category
stringclasses
107 values
title
stringlengths
15
179
question_link
stringlengths
59
147
question_body
stringlengths
53
33.8k
answer_html
stringlengths
0
28.8k
__index_level_0__
int64
0
1.58k
acid base equilibrium
Auto-ionization equilibrium of water shifted with acid-base addition?
https://chemistry.stackexchange.com/questions/129275/auto-ionization-equilibrium-of-water-shifted-with-acid-base-addition
<p>Adding acids or bases to water, so that either pH or pOH decreases independently of the other, will that affect the auto-ionization of water? For example, pure water + auto-ionized state, with some base added to remove some protons, will it auto-ionize a bit more (create more H+ and OH-) or a bit less (remove some H...
<p>It depends how you write the reaction.</p> <blockquote> <p>For example, pure water + auto-ionized state, with some base added to remove some protons, will it auto-ionize a bit more (create more H+ and OH-) or a bit less (remove some H+ and OH-)?</p> </blockquote> <p>If we call the base <span class="math-containe...
162
acid base equilibrium
Confused about weak/strong acids, conjugated acid-base pairs and buffers
https://chemistry.stackexchange.com/questions/55059/confused-about-weak-strong-acids-conjugated-acid-base-pairs-and-buffers
<p>I learned that </p> <p>a) the conjugate base to a weak acid is a strong base (and vice versa).</p> <p>b) a buffer consists of a weak acid (base) and its conjugate base (acid). </p> <p>However, <a href="http://chemcollective.org/activities/tutorials/buffers/buffers3" rel="nofollow">this</a> explanation of buffers ...
<p>A strong acid (or base) forms a weak conjugate base (or acid). This is correct. By saying that $\ce{HA}$ is a weak acid and $\ce{A-}$ is a weak conjugate base they mean:</p> <ul> <li>Acid shouldn't be too strong - don't use $\ce{NaCl + HCl }$ </li> <li>Conjugated base shouldn't be too strong - don't use $\ce{EtOH/...
163
acid base equilibrium
Are there acid/base processes in aqueous solution that are so slow that they are kinetically controlled?
https://chemistry.stackexchange.com/questions/133203/are-there-acid-base-processes-in-aqueous-solution-that-are-so-slow-that-they-are
<p>This question came up in figuring out what the fundamental differences are between redox chemistry and acid/base chemistry (if any).</p> <p>In redox chemistry, strong oxidants and strong reductants can co-exist in solution because they react slowly with each other (or not at all). An example from biology is a low N...
<p>Since water is a protic solvent, the predominant form of aqueous acid-base reactions involve proton transfer and that mechanism tends to be quite fast.</p> <p>But not always.</p> <p>Most readers are familiar with the use of phenolphthalein as an indicator for titrating acid solutions with a strong base such as sodiu...
164
acid base equilibrium
Predicting acid-base equilibria
https://chemistry.stackexchange.com/questions/168215/predicting-acid-base-equilibria
<p>I was looking at acid-base equilibria of weak acids and weak bases. To determine the equilibrium constant of a reaction of those, I found a formula on the libretexts page:</p> <p><a href="https://i.sstatic.net/ndfSk.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/ndfSk.png" alt="enter image descriptio...
<p>Consider a generic acid dissociation reaction of the form:</p> <p><span class="math-container">$$\ce{HE &lt;=&gt; H^+ + E^-}$$</span></p> <p>Let:</p> <p><span class="math-container">$A$</span> represent <span class="math-container">$HE$</span></p> <p><span class="math-container">$B$</span> represent <span class="mat...
165
acid base equilibrium
Which acid/base does a strong base/acid react when added to a buffer solution?
https://chemistry.stackexchange.com/questions/111957/which-acid-base-does-a-strong-base-acid-react-when-added-to-a-buffer-solution
<p>I'm in high school chemistry and just learning about buffer solutions. For example, given a buffered solution of <span class="math-container">$\ce{CH3COOH}$</span> and <span class="math-container">$\ce{NaCH3COO}$</span> with <span class="math-container">$K_a = 1.8 \times 10^{-5}$</span>, we might want to find what t...
<p><span class="math-container">$$\ce{CH3COOH + H2O &lt;=&gt; H3O+ + CH3COO-}$$</span></p> <blockquote> <p>My question is, which acid (CH3COOH or the conjugate H3O+) will the base KOH react with?</p> </blockquote> <p>You have to satisfy two equilibria, the one you wrote and the auto-dissociation of water.</p> <p><...
166
acid base equilibrium
competing solubility and acid-base equilibria
https://chemistry.stackexchange.com/questions/188551/competing-solubility-and-acid-base-equilibria
<p>Fluorides such as <span class="math-container">$\ce{CaF2}$</span> or <span class="math-container">$\ce{LiF}$</span> are sparingly soluble in water. Does their solubility product constant <span class="math-container">$K_\text{sp}$</span> about the equilibrium of</p> <p><span class="math-container">$$\ce{CaF2 &lt;&lt...
167
acid base equilibrium
How to find the concentrations of the acid-base equilibrium between sulfuric acid and sulfur dioxide for a known pH using Octave?
https://chemistry.stackexchange.com/questions/34924/how-to-find-the-concentrations-of-the-acid-base-equilibrium-between-sulfuric-aci
<p>The system is an aqueous solution of sulfuric acid and sulfur dioxide. I know how much sulfur there is and I know the pH. The system is in equilibrium. I would like to use Octave to solve the system.</p> <p>I set up the following equations, ignoring $\ce{SO3^2-}$ because the pH is around 1.5.</p> <p>By definitio...
<p>Your code seems to be calculating the <em>differences</em> between a guessed concentration vector <code>x</code> and a calculated concentration vector. These differences in concentrations between guessed and calculated are <code>y</code>. For example, the guessed pH is apparently <code>x(1)</code>, and the calcula...
168
acid base equilibrium
Equilibrium constant for the neutralization of weak acid by strong base
https://chemistry.stackexchange.com/questions/109948/equilibrium-constant-for-the-neutralization-of-weak-acid-by-strong-base
<blockquote> <p>Acetic acid has a <span class="math-container">$K_\mathrm{a}$</span> of <span class="math-container">$\pu{1.8e-5}$</span>. What is the equilibrium constant for the neutralization of this acid with <span class="math-container">$\ce{NaOH}$</span>?</p> </blockquote> <p>Given acetic acid</p> <p><span cl...
<p>Sodium hydroxide is a strong base and is supposed to be fully dissociated. You then should've started by writing down the neutralization reaction itself for which you have to determine the equilibrium constant <span class="math-container">$K$</span> and unravel a tangle from there:</p> <p><span class="math-containe...
169
acid base equilibrium
Understanding weak acid-strong base titration
https://chemistry.stackexchange.com/questions/158751/understanding-weak-acid-strong-base-titration
<p>Today I stumbled across a website which defined the titration of weak acid and strong base as the following:</p> <p>&quot;The titration of a weak acid with a strong base involves the direct transfer of protons from the weak acid to the hydoxide ion. The reaction of the weak acid, acetic acid, with a strong base, NaO...
<p>Your second equation is an equilibrium. Both acetic acid and acetate ions are always present in a solution, although their proportion may vary. When <span class="math-container">$\ce{CH3COOH}$</span> is dissolved into water, a fraction of the molecules are transformed by reaction with water, producing some <span cla...
170
acid base equilibrium
How to estimate the equilibrium constant of the reaction between NaF and HCl
https://chemistry.stackexchange.com/questions/39406/how-to-estimate-the-equilibrium-constant-of-the-reaction-between-naf-and-hcl
<p>Since $\ce{HCl}$ is more acidic than $\ce{HF}$, the left hand side of a reaction has a stronger acid than the right hand side.</p> <p>Since $\ce{NaF}$ is more basic than $\ce{NaCl}$, the left hand side has a stronger base relative to the right hand side.</p> <p>$$\begin{align}\text{Stronger Acid/Base} &amp; \ce{-&...
<p>We can entirely ignore the sodium cation; it is only a spectator ion. This means, the reaction we are observing is:</p> <p>$$\ce{HCl + F- &lt;=&gt; Cl- + HF}\tag{1}$$</p> <p>The equilibrium constant for this reaction is:</p> <p>$$K = \frac{[\ce{Cl-}][\ce{HF}]}{[\ce{HCl}][\ce{F-}]}\tag{2}$$</p> <p>We can expand t...
171
acid base equilibrium
Why does pKa of a acid-base indicator equal to the pH when the equivalence point is reached?
https://chemistry.stackexchange.com/questions/29697/why-does-pka-of-a-acid-base-indicator-equal-to-the-ph-when-the-equivalence-point
<p>To be honest, I just don't get it. I had this question while reading a Chemguide article, on this topic: <img src="https://i.sstatic.net/AMrse.jpg" alt="enter image description here"></p> <p>I think my confusion is caused by the way I look at pKa of acid-base indicator. Should you think of it more as a reaction quo...
<p>Look at the following equation:</p> <blockquote> <p>$$\mathrm{pH} = \mathrm pK_{\mathrm a} + \log\frac{[\ce{A^-}]}{[\ce{HA}]}$$</p> </blockquote> <p>At the <em>half equivalence point</em>, say we have 10 moles of $\ce{WA},$ and so there will be 5 moles of $\ce{SB}$ as the name suggests ("half equivalence"). So w...
172
acid base equilibrium
Which of the following can be a source of error in Spectrophotometry? Mark the wrong answer
https://chemistry.stackexchange.com/questions/145857/which-of-the-following-can-be-a-source-of-error-in-spectrophotometry-mark-the-w
<p>a) Differences in solvent</p> <p>b) Acid base equilibrium (differences of pH)</p> <p>c) Parasitic or stray radiation</p> <p>d) Monochromatic radiation</p> <p>I have some doubts about pH in spectrophotometry. I'm not sure if it is correct but here is what I thought:</p> <p>a)Differences in solvent. It can be a source...
<p>It is a very open ended question, but first three choices will cause errors. Regarding your pH issue, you are right, it is multiplicative error. Take the example of phenolphthalein, as you say that its color (=absorption spectrum) is different in acidic or basic medium. So pH change can shift the lambda max of analy...
173
acid base equilibrium
How to calculate he equilibrium constant change for acid-base reactions in a different solvent?
https://chemistry.stackexchange.com/questions/85644/how-to-calculate-he-equilibrium-constant-change-for-acid-base-reactions-in-a-dif
<p>So we know that $K_\mathrm w$ is $10^{-14}$. But what if I am working with non-aqueous systems? Suppose I were to add LDA to liquid ammonia, or dissolve HCl in concentrated sulfuric acid. How would I calculate the percentage of dissociation? I have some inkling of how to do this but I don't really see discussions on...
<p>For all solvents that can dissociate into ions, a dissociation constant can indeed be measured. Expect them to be unpredictable in each direction.</p> <p>Furthermore, the $\mathrm pK_\mathrm a$ values you know are typically those measured in water, although some organic chemists rely more heavily on the DMSO tables...
174
acid base equilibrium
A simple equilibrium problem
https://chemistry.stackexchange.com/questions/99890/a-simple-equilibrium-problem
<p>Take the following simple equilibrium: $$\ce{CH3COOH + H2O &lt;=&gt; H3O+ + CH3COO-}$$</p> <p>Ethanoic acid will act as a typical Brønsted-Lowry acid and donate a proton to water, forming a conjugate acid-base pair. In this case, H<sub>3</sub>O<sup>+</sup> is the conjugate acid, and CH<sub>3</sub>COO<sup>-</sup> is...
<p>You are neglecting the hydronium ions produced during dissociation of acetic acid.</p> <p>We can consider the following sequence of events when we add more acetic acid to solution. In reality they occur simultaneously, but it's easier to think about it sequentially.</p> <ol> <li>We have more than the equilibrium c...
175
acid base equilibrium
What actually happens in strong acid- weak base reactions?
https://chemistry.stackexchange.com/questions/134540/what-actually-happens-in-strong-acid-weak-base-reactions
<p>I'm going back through my notes from a chemistry class, which I did well in despite not having a very good conceptual understanding, in order to hopefully develop that understanding, but there's something I can't find in the book or online. Why is it that, when solving for the pH of a solution that results from the ...
<p><strong>The strategy of major species</strong></p> <p>You correctly describe the strategy. First, let reactions go to completion (in the direction that makes sense, i.e. weak base and strong acid forms weak acid and spectator ion - never the other way around). Then, check what the major species are and estimate the...
176
acid base equilibrium
Why does equilibrium favour weak acid or weak base?
https://chemistry.stackexchange.com/questions/38831/why-does-equilibrium-favour-weak-acid-or-weak-base
<p>For example, in the reaction $\ce{NaOH +HCl-&gt;NaCl +H_2O}$, the products are favoured by a factor of approximately $10^{24}$. Is this a general rule? Is it because the products are more stable than the reactants?</p>
<p>Here is a simple intuitive explanation. In your above example, there is actually 2 reactions occurring, the forward and the reverse reaction. Let us consider the forward reaction. Here, both $\ce{NaOH}$ and $\ce{HCl}$ are strong bases and acids. What this means is that HCl has a strong ability to donate a proton and...
177
acid base equilibrium
Determine which ion, H3O+ or OH-, is in excess at the end of the reaction
https://chemistry.stackexchange.com/questions/147865/determine-which-ion-h3o-or-oh-is-in-excess-at-the-end-of-the-reaction
<p>How would you know when an acid or base is paired with <span class="math-container">$\ce{H2O}$</span> that it will form an <span class="math-container">$\ce{OH-}$</span> ion or a <span class="math-container">$\ce{H3O+}$</span> ion? I just started the acid and base equilibrium unit, and I'm just confused on what cond...
<p>Acids are hydrogen ion donors. When the react with water, they can give a hydrogen ion to form <span class="math-container">$ \ce{H3O+}$</span>.<br/> For example:<br/></p> <p><span class="math-container">$ \ce{HCl(aq) + H2O(l) \rightarrow Cl-(aq) + H3O+(aq)}$</span></p> <p>Simple acids, such as <span class="math-c...
178
acid base equilibrium
What are the concentration changes when diluting an equimolar acetic acid: acetate buffer?
https://chemistry.stackexchange.com/questions/109968/what-are-the-concentration-changes-when-diluting-an-equimolar-acetic-acid-aceta
<p>When a buffer (for example, a mixture of 100 mM acetic acid and 100 mM acetate), is diluted 10-fold, all the concentrations change drastically. Surprisingly, after re-establishment of equilibrium, the pH is not much different from the starting pH.</p> <p>How can you visualize how diluting a buffer disturbs the equi...
<p>Consider an acid buffer with <span class="math-container">$pK_a=5$</span>. Ignore the hydroxyl concentration, assuming it is negligible.</p> <p>Dilution leads to an identical (proportional) reduction in the concentration of all solutes: undissociated acid, complementary base (anion), and protium. Because the concen...
179
acid base equilibrium
Base/acid reaction -&gt; alcohol amphoteric? why no pkb value?
https://chemistry.stackexchange.com/questions/145185/base-acid-reaction-alcohol-amphoteric-why-no-pkb-value
<p>I have a question concerning acid/base reactions. Is it true that an alcohol is a better base than water? My Professor listed the basicity (because we talked about E1/E2 and Sn1/Sn2 reactions) of the following compounds the following way: RO- &gt; OH- &gt; ROH &gt; H2O (with stronger base being the RO- and the weake...
180
acid base equilibrium
What happens if I have an acid/base equillibrium and remove hydronium ions until there is 50/50 of acid and conjugate base?
https://chemistry.stackexchange.com/questions/27146/what-happens-if-i-have-an-acid-base-equillibrium-and-remove-hydronium-ions-until
<p>Suppose I had an acid HA, and it reaches equilibrium in water. Then I remove the hydronium ions. I don't know how I would do this, maybe adding some hydroxide ions. My question is can I do this and will I be able to eventually create a 50/50 mixture of acid and conjugate base? Is this a very good buffer?</p>
<p>You can't just remove hydronium ions because the solution needs to remain electrically neutral.</p> <p>You can't just add hydroxide ions, but you could add sodium hydroxide until the HA/A- ratio was 50/50.</p> <blockquote> <p>Is this a very good buffer?</p> </blockquote> <p>It is the optimum ratio of HA and A- ...
181
acid base equilibrium
What solution is not in equilibrium?
https://chemistry.stackexchange.com/questions/81550/what-solution-is-not-in-equilibrium
<blockquote> <p>An example of a solution not in equilibrium<br> (A) Chemical ph indicator<br> (B) Acid/base buffer<br> (C) Anhydrous solution<br> (D) hypotonic solution<br> (E) Supersaturated solution</p> </blockquote> <p>I eliminated A and B. Then, I chose E, which is a right answer. Nonetheless, I r...
182
acid base equilibrium
Does concentration or pKa define acid strength?
https://chemistry.stackexchange.com/questions/105242/does-concentration-or-pka-define-acid-strength
<p>For example, is 3M HCl a stronger acid than 1M HCl? </p> <p>I would reason that the concentration of an acid/base does not influence its strength. Strength is determined by the pKa, and, as per Le Chatelier's Principle, the initial concentration does not influence the equilibrium constant. </p> <p>It ...
<p>The term ‘strong acid’ is sometimes used in a rather fuzzy way and you ran into problems doing so. I prefer to use the term ‘strong acid’ <em>only</em> with respect to an acid’s <span class="math-container">$\mathrm pK_\mathrm{a}$</span> value and disregard all other influences. This gives a clearly defined measure ...
183
acid base equilibrium
How do you know is a solution is acid or basic when you dissolve a weak acid/base?
https://chemistry.stackexchange.com/questions/123428/how-do-you-know-is-a-solution-is-acid-or-basic-when-you-dissolve-a-weak-acid-bas
<p>If I dissolve the weak acid HCN into water, I get a solution of oxonium and CN ions and since there is an equilibrium there is more HCN left.</p> <p>So I thought CN ions can consequently react with water to form hydroxide-ions, which is a weak base-reaction, by which we also get the original HCN molecules. I am co...
<p>There are 3 equilibriums, described by 3 equilibrium constants:</p> <p>The first one is the equilibrium of water dissociation:</p> <p><span class="math-container">$$\ce{H2O &lt;&lt;=&gt;H+ + OH-}$$</span></p> <p><span class="math-container">$$K_\mathrm{w}=[\ce{H+}][\ce{OH-}]$$</span></p> <hr /> <p>The second one is ...
184
acid base equilibrium
Algebraic treatment of equilibrium
https://chemistry.stackexchange.com/questions/131643/algebraic-treatment-of-equilibrium
<p>This is from Laitinen and Harris, "Chemical Analysis, An Advanced Text &amp; Reference" which describes a simple acid-base equilibrium. They derive a relation in the end directly. I haven't seen this expression in many books which teach solution equilibria. The authors cite an article from the Journal of Chemical Ed...
<p>There is only one source of hydroxyl ions, ionization of water (Eq. 3 in the OP). Ionized water contributes equal amounts of hydroxyl and hydronium ion. Similarly, dissociation of acid <span class="math-container">$\ce{HA}$</span> results in equal amounts of hydronium and of conjugate base <span class="math-containe...
185
acid base equilibrium
In acid/base chemistry, are there amphoteric substances that undergo something that resembles disproportionation in redox chemistry
https://chemistry.stackexchange.com/questions/133202/in-acid-base-chemistry-are-there-amphoteric-substances-that-undergo-something-t
<p>Some substances disproportionate. This means a species with an intermediate oxidation state yields two species with higher and lower oxidation state. For example:</p> <p><span class="math-container">$$\ce{Hg2Cl2 -&gt; Hg + HgCl2}$$</span></p> <p>My question is if there are substance that have the analogous acid/ba...
<p>As I mentioned in the comments, I know of one case where a polyprotic acid has a second proton which is more acidic than the first: the aqueous pervanadyl complex, <span class="math-container">$\ce{[VO_2(H_2O)_4]^+}$</span>. <a href="https://en.wikipedia.org/wiki/Acid_dissociation_constant#Polyprotic_acids" rel="nor...
186
acid base equilibrium
Calculating error in acid-base titration
https://chemistry.stackexchange.com/questions/171766/calculating-error-in-acid-base-titration
<p>You perform a titration of an acid (let's say <span class="math-container">$\pu{20 ml}$</span> <span class="math-container">$\ce{CH_3COOH}$</span>) with a base (let's say <span class="math-container">$\pu{0.5 M}$</span> <span class="math-container">$\ce{NaOH}$</span>). The burette is marked at <span class="math-cont...
187
acid base equilibrium
How do salts of a weak acid + weak base behave in solution?
https://chemistry.stackexchange.com/questions/82959/how-do-salts-of-a-weak-acid-weak-base-behave-in-solution
<p>Say you have Ammonium Formate in solution, the salt formed by the reaction of Formic Acid and Ammonia. Would both the Formate ion and Ammonium ion protonate and deprotonate, respectively, to form their conjugates until equilibrium is reached? I would also assume that one of the ions would form more of their conjug...
188
acid base equilibrium
Why do acids usually completely react with bases?
https://chemistry.stackexchange.com/questions/22208/why-do-acids-usually-completely-react-with-bases
<p>When a neutralisation reaction happens, for example, <span class="math-container">$ \pu{100 mol l^-1}$</span> of <span class="math-container">$\ce{HCl}$</span> with <span class="math-container">$\pu{100 mol l^-1}$</span> <span class="math-container">$\ce{NH_3}$</span>, why does <em>all</em> of the base and acid get ...
<p>Acids and bases don't necessarily completely react with each other. Consider your hypothetical reaction between hydrochloric acid and ammonia. </p> <p><span class="math-container">\begin{align} \ce{HCl + H3N &amp;-&gt; H4N+ + Cl-}&amp; \text{Extent:}&amp; \approx100\% \end{align}</span></p> <p>The products are <s...
189
acid base equilibrium
What is the difference between the titration of a strong acid with a strong base and that of the titration of a weak acid with a strong base?
https://chemistry.stackexchange.com/questions/4081/what-is-the-difference-between-the-titration-of-a-strong-acid-with-a-strong-base
<blockquote> <p>Which of the following statements best characterizes the difference between the titration of a strong acid with a strong base and that of the titration of a weak acid with a strong base?</p> <p>A) Both the strong acid and the strong base are completely dissociated in solution whereas the weak aci...
<p>The answer is A.</p> <p>Let's look at a weak acid: acetic acid. It has a $K_a$ of $1.8\cdot 10^{-5}$. From this you can calculate how much it will dissociate in water. Let's say we have a concentration of $1~\mathrm{M}$:</p> <p>\begin{align} K_a &amp;= \frac{[\ce{CH3COO^{-}}][\ce{H+}]}{[\ce{CH3COOH}]}\\ 1.8 \cdot...
190
acid base equilibrium
Do weak acid/weak base neutralisation reactions go to completion?
https://chemistry.stackexchange.com/questions/83429/do-weak-acid-weak-base-neutralisation-reactions-go-to-completion
<p>I'm wondering if reactions that involve a weak acid and a weak base go to completion. For example, say we have equal amounts and equal volumes of acetic acid and ammonia being mixed together. Would this neutralisation reaction go to completion or would it reach a state of equilibrium?</p> <p>$\ce{NH_3 + CH_3COOH &l...
<p>Weak acids and bases do indeed remain in an equilibrium state with a certain concentration of the free acid and the free base alongside a certain concentration of the deprotonated acid anion and the protonated base cation.</p> <p>In general, you can consider any acid-base reaction to be essentially the following:</p...
191
acid base equilibrium
What pH indicators are commonly used for non-polar medium?
https://chemistry.stackexchange.com/questions/87521/what-ph-indicators-are-commonly-used-for-non-polar-medium
<p>Compounds, commonly used as <a href="https://en.wikipedia.org/wiki/PH_indicator" rel="nofollow noreferrer">pH-indicators</a>, are soluble in aqueous media and polar solvents (DMSO, DMF, NMP etc.) and are functional pretty much across all these solvents. However, practically none these indicators are soluble in non-p...
192
acid base equilibrium
Why isn&#39;t nitrous acid a product of nitrite and water?
https://chemistry.stackexchange.com/questions/8862/why-isnt-nitrous-acid-a-product-of-nitrite-and-water
<blockquote> <p><strong>Question</strong><br> Predict the products of the following acid-base reactions, and predict whether the equilibrium lies to the left or to the right of the equations $$\ce{NO2- + H2O -&gt; ?}$$</p> </blockquote> <p>I thought it would be $\ce{NO2- + H2O -&gt; HNO2 + OH-}$, but my textbook...
<p>It should form nitrous acid... If it was $NO_3^{-}$, nitrate ion, then it would presumably form nitric acid $HNO_3$.</p> <p>Nitrous acid reacts with water to form nitrite and hydronium:</p> <p>$$\ce{HNO_2 + H_2O -&gt; NO_2^- + H_3O^+} $$</p> <p>Water is an amphoteric species. Assuming we just have water the nitri...
193
acid base equilibrium
Why must a buffer solution contain both a weak acid and a salt solution of its conjugate base?
https://chemistry.stackexchange.com/questions/105646/why-must-a-buffer-solution-contain-both-a-weak-acid-and-a-salt-solution-of-its-c
<p>Doesn’t the weak acid dissociate to produce the conjugate base on its own? </p> <p>I understand that when a strong base is added to the buffer solution, the hydroxide ions will react with the hydrogen ions formed via the dissociation of the weak acid. The equilibrium position will shift rightwards to replenish thes...
<p>You are correct that a weak acid will only partially dissociate in water. Taking for example the weakly acidic salt <span class="math-container">$\ce{NH4Cl}$</span> of which the ammonium cation is acidic, in water we get reaction (1).</p> <p><span class="math-container">$$\ce{NH4+ + H2O &lt;=&gt; NH3 + H3O+}\tag{1}...
194
acid base equilibrium
EQPt pH of a Monoprotic Acid-Base Titration: Product of Molarites Over Their Sum
https://chemistry.stackexchange.com/questions/99538/eqpt-ph-of-a-monoprotic-acid-base-titration-product-of-molarites-over-their-sum
<h2>Context</h2> <p>The Henderson-Hasselbalch equation is as follows. $$pH=-\log\big(K_a\big)+\log\bigg(\frac{[A^-]}{[HA]}\bigg)$$ One may follow <a href="https://en.wikipedia.org/wiki/Henderson%E2%80%93Hasselbalch_equation#Derivation" rel="nofollow noreferrer">its derivation</a> in order to understand how it came to ...
195
acid base equilibrium
Why is the hydrolysis of the conjugate base of a weak acid neglected in buffer solutions?
https://chemistry.stackexchange.com/questions/82963/why-is-the-hydrolysis-of-the-conjugate-base-of-a-weak-acid-neglected-in-buffer-s
<p>Consider a solution which contains a weak acid and the salt of its conjugate base with a strong base. e.g. $$\ce{CH3COOH + H2O &lt;=&gt;[$K_\rm{a}$] CH3COO- + H3O+}\tag1$$ $$\ce{CH3COO- + H2O &lt;=&gt;[$K_\rm{h}$] CH3COOH + OH-}\tag2$$</p> <p>Now, $\displaystyle{K_\rm{a} = \frac{[\ce{H3O+}] [\ce{CH3COO-}]}{[\ce{CH...
<p>$\mathrm{p}K_\mathrm{a} = 4.75$, therefore $K_\mathrm{a} = 10^{-4.75}$. Thus,</p> <p>$$K_\mathrm{a} = \frac{[\ce{AcO^-}][\ce{H+}]}{[\ce{AcOH}]}$$</p> <p>So, let's assume $[\ce{AcOH}] = \pu{1.0 M}$. Just to get a feel, how far the acid is dissociated:</p> <p>$$K_\mathrm{a} = \frac{x \cdot x}{\pu{1.0 M}} \to x = \s...
196
acid base equilibrium
Weak acid and weak base salt hydrolysis
https://chemistry.stackexchange.com/questions/85650/weak-acid-and-weak-base-salt-hydrolysis
<p>While solving for weak acid and weak base salt hydrolysis, why do we take the degree of hydrolysis for both the anion and cation to be the same?</p> <p>If we assume they are the same, when solving for $K_\mathrm{a}$ and $K_\mathrm{b}$ for the cation and anion using simultaneous equilibrium, I always get them to be ...
197
acid base equilibrium
Is equilibrium point for a coupled equilibria of arbitary number of coupled reactions is a unique point?
https://chemistry.stackexchange.com/questions/152689/is-equilibrium-point-for-a-coupled-equilibria-of-arbitary-number-of-coupled-reac
<p>I was solving a question of salt hydrolysis for a mixture of Weak Acid-Base Salts, given the initial amount of salt and Equilibrium constants. I was trying to approach the problem in two ways, Assuming initially that we have all reactants and no products and move the reaction forward OR assuming all the reactants ha...
<p>One of the first experimental demonstrations that the same equilibrium point is reached if the reaction starts with all reactants or all products was <span class="math-container">$\ce{2HI&lt;=&gt;I_2 + H_2}$</span> made by Bodenstein in <span class="math-container">$\approx 1894$</span>. I have redrawn the data.</p>...
198
acid base equilibrium
How exactly does a buffer made up of a weak acid and its conjugate base work upon addition of hydroxide ions?
https://chemistry.stackexchange.com/questions/153741/how-exactly-does-a-buffer-made-up-of-a-weak-acid-and-its-conjugate-base-work-upo
<p>Consider a buffer solution containing a weak acid and its conjugate base (<span class="math-container">$c_\mathrm{total} = \pu{0.1 mol L-1}$</span>): <span class="math-container">$$\ce{HA &lt;=&gt; H^+ + A^-}$$</span></p> <p>When <span class="math-container">$\ce{H+}$</span> ions are added (from a strong acid), the ...
<p>During neutralization of the buffer by a strong base solution, there are ongoing three reversible reactions, maintaining three equilibria:</p> <p><span class="math-container">$$ \begin{align} \ce{H2O + A- &amp;&lt;=&gt; OH- + HA} &amp;\quad K_\mathrm{b} &amp;= \frac{\ce{[OH-][HA]}}{\ce{[A-]}} \tag{1}\\ \ce{H2O &amp...
199
oxidation states
Oxidation States?
https://chemistry.stackexchange.com/questions/68558/oxidation-states
<p>Metals in low Oxidation states are usually reducing agents. Is there any example of a metal in zero Oxidation state acting as an oxidizing agent. </p>
<p>As with pretty much every "is there ______?" in chemistry, the answer is yes, there is.</p> <p>Of course, using the pure <em>metal</em> itself as an oxidising agent would be really tough. However, if you use certain tricks to stabilise the negative oxidation state, it is possible. For example, π-acceptor ligands su...
200
oxidation states
variable oxidation states
https://chemistry.stackexchange.com/questions/147911/variable-oxidation-states
<p>which of the statements is true:</p> <ol> <li><p>looking at the electronic configuration of an element, can the possible oxidation states/oxidation number of an elemnet be predicted. for example, the valence electronic configuration of nitrogen is 2s^2 2p^3. From this can we know all the possible oxidation states ex...
<p>The oxidation numbers cannot be predicted from the structure of the atom. They are experimentally determined. Not much chance you predict that while nitrogen can get all integer oxidation numbers from <span class="math-container">$−3$</span> to <span class="math-container">$+5$</span>, its neighbor oxygen can only h...
201
oxidation states
Oxidation states of oxygen
https://chemistry.stackexchange.com/questions/60961/oxidation-states-of-oxygen
<p>I'm given a question:</p> <blockquote> <p>Oxidation number of $\ce{O}$ in $\ce{BaO2}$ is $x$ and in $\ce{OF2}$ is $y$; then the value of $x+y$ is what?</p> </blockquote> <p>Now my main question is that if $\ce{F}$ has $-1$ valency in $\ce{OF2}$ then $\ce{O}$ must have valency of $+2$. But is that possible sin...
<p>The concept of oxidation state simply works on concept of electronegativity.The more electronegative atom acquire a negative charge while less electronegative atom acquire a positive charge. Depending on this hypothesis oxygen have 5 oxidation states.</p> <ol> <li><p>In all the oxides,oxygen has an oxidation state ...
202
oxidation states
What are oxidation states used for?
https://chemistry.stackexchange.com/questions/61040/what-are-oxidation-states-used-for
<p>When I took high school chemistry many years ago, considerable effort was spent on teaching us to <em>compute</em> oxidation states of atoms in various compounds, following a set of rules that looked somewhat arbitrary to me at the time. As far as I remember, we were never told what benefits (other than passing test...
<p>Of course they are useful. Perhaps you have not come across them yet, but being able to determine the oxidation state of an atom allows us to understand the properties of chemicals and how redox reactions work.</p> <p>Let's just give two very simple examples. There are tons more. (I don't even want to go into organ...
203
oxidation states
Unusual oxidation states of alkali metals
https://chemistry.stackexchange.com/questions/109846/unusual-oxidation-states-of-alkali-metals
<p>When going through list of oxidation states on <a href="https://en.m.wikipedia.org/wiki/List_of_oxidation_states_of_the_elements" rel="noreferrer">Wikipedia</a> I encounterd there that sodium, potassium, rubidium and caesium exhibit oxidation states of -1, but not lithium, even though its electronegativity is more ...
<p>You are talking about alkalides, salts where the anion is an alkali metal. There is a very brief overview on <a href="https://en.wikipedia.org/wiki/Alkalide" rel="noreferrer">Wikipedia</a> which also provides a couple of examples, including <span class="math-container">$\ce{[Na(\text{cryptand[2.2.2]})]+Na-}$</span>....
204
oxidation states
Elements with multiple oxidation states
https://chemistry.stackexchange.com/questions/60679/elements-with-multiple-oxidation-states
<p>I downloaded a periodic table app which gives detailed information for each element. The app shows some elements, however, have two different oxidation states. Hydrogen, for instance, can have either a 1+ or 1- state. What do these two states signify? Why do these elements have <em>more</em> than one oxidation state...
<p>The oxidation state of an element in a compound is simply decided on the basis of electronegativity of other atoms. As the definition of oxidation state says </p> <blockquote> <p>Oxidation state of an element in a given compound is the charged acquired by its atom on the basis of electronegativity of other atom...
205
oxidation states
Explaining the oxidation states of palladium
https://chemistry.stackexchange.com/questions/7705/explaining-the-oxidation-states-of-palladium
<p>Palladium follows an exception to normal electron filling-up rules and so has the electron configuration of $\ce{[Kr] 4d^{10} 5s^0}$</p> <p>The oxidation states of palladium are $\ce{+II}$ and $\ce{+IV}$. How can these oxidation states be explained by looking at the special electron configuration of $\ce{Pd}$? </...
<p>Ions of the transition metals do not often occur "naked" the way one might think of a sodium ion. Of course, sodium ions cannot occur by themselves either, but let's compare the two for a moment. </p> <blockquote> <p>Sodium nitrate, $\ce{NaNO3}$</p> </blockquote> <p>When $\ce{NaNO3}$ dissolves in water, the two ...
206
oxidation states
Anomalous oxidation states of Transition Metals
https://chemistry.stackexchange.com/questions/59926/anomalous-oxidation-states-of-transition-metals
<p><a href="https://i.sstatic.net/5huav.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/5huav.png" alt="enter image description here"></a></p> <blockquote> <p>I have noted down the available positive oxidation states of the first row of transition elements (on the Periodic Table) from the respective...
<p>Regarding the maximum oxidation state achievable, there are two competing trends. Both have to do with ionisation energies.</p> <p>In going to a higher oxidation state, the additional IEs are always balanced against the release in energy in the formation of stronger ionic/covalent bonds. However, if the additional ...
207
oxidation states
Oxidation states of Thiosulphate
https://chemistry.stackexchange.com/questions/178247/oxidation-states-of-thiosulphate
<p><a href="https://i.sstatic.net/YjBmj.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/YjBmj.png" alt="enter image description here" /></a></p> <p>I was given this question and don't understand why the two sulphur atoms have different oxidation states - and how to actually figure it out. Could someone p...
<p>If the last paragraph in your quotation is meant to be the book's answer, I would stain that text with my intensely colored, anthocyanin-rich cranberry jam*. I would find either <span class="math-container">$-1$</span> and <span class="math-container">$+5$</span> or <span class="math-container">$0$</span> and <span ...
208
oxidation states
Plutonium having more oxidation states than samarium?
https://chemistry.stackexchange.com/questions/7704/plutonium-having-more-oxidation-states-than-samarium
<p>Why does plutonium have more oxidation states than samarium?</p> <p>Electron configuration of Pu: <span class="math-container">$\ce{[Rn] 5f^6 7s^2}$</span></p> <p>Electron configuration of Sm: <span class="math-container">$\ce{[Xe] 4f^6 6s^2}$</span></p> <p>I thought that only the valence electrons affected the oxid...
<p>This is yet another interesting effect of <a href="http://web.archive.org/web/20150511024324/http://depa.fquim.unam.mx/amyd/archivero/LecturasobreNodosRadiales_12854.pdf" rel="nofollow noreferrer">the anomalous compactness of orbitals in the first appearance of each type of subshell</a> (<span class="math-container"...
209
oxidation states
Negative oxidation states of Si
https://chemistry.stackexchange.com/questions/37209/negative-oxidation-states-of-si
<p>According to <em><a href="https://en.wikipedia.org/wiki/List_of_oxidation_states_of_the_elements" rel="noreferrer">List of oxidation states of the elements</a></em>, silicon has a possible oxidation state of $-4$.</p> <p><a href="https://i.sstatic.net/xpktm.jpg" rel="noreferrer"><img src="https://i.sstatic.net/xpkt...
<p>I am not sure if Silane ($\ce{SiH_4}$) can really be considered. </p> <p>But there are <a href="http://www.wikiwand.com/en/Silicide" rel="noreferrer">silicides</a> which silicon forms with strongly electropositive metals. In these compounds, silicon has a negative oxidation state.</p> <p>For <a href="http://www.wi...
210
oxidation states
Why are multiple oxidation states useful for a catalyst?
https://chemistry.stackexchange.com/questions/28828/why-are-multiple-oxidation-states-useful-for-a-catalyst
<p>Transition elements are good catalysts because they have multiple oxidation states?Why multiple oxidation states matter?</p>
<p>The answer has a lot to do with "what is a catalyst in the first place?" A catalyst is a compound that can affect the rate of a chemical reaction by providing an alternative and lower energy profile or pathway. That is, it is a substance that makes it so that A -> B at a lower energy cost. But it only has an effect...
211
oxidation states
Covalency of metal oxides in high oxidation states
https://chemistry.stackexchange.com/questions/128634/covalency-of-metal-oxides-in-high-oxidation-states
<p>So, metal oxides are generally basic, right? But in higher oxidation states their covalent character is predominant. For example in Mn2O7 the Mn - O bond is covalent. Why is that?</p>
<p>Metal oxides are not always basic. In many cases where the bonding is strongly ionic, the oxide ions do act as a base. However, if the metal is in a high oxidation state an ionic bond would require a prohibitively high charge on the metal ion; the ionization energy required to put seven positive charges on one man...
212
oxidation states
What are the oxidation states in Borohydride (BH4-)
https://chemistry.stackexchange.com/questions/14038/what-are-the-oxidation-states-in-borohydride-bh4
<p>The CRC Elecrochemical Series and the solution to our exercise suggest that the oxidation states of borohydride are -V for Boron and +I for Hydrogen.</p> <p>Since H (2.2) is more electronegativ than B (2.0), I would have expected the oxidation states to be +III for B and -I for H.</p> <p>What am I missing here?</p...
<blockquote> <p>I would have expected the oxidation states to be +III for B and -I for H.</p> </blockquote> <p>You're right, boron is in the (+3) oxidation state in these equations.</p> <p>In $\ce{B(OH)_3}$ each $\ce{OH}$ is (-1) and the boron is (+3), overall the molecule is neutral</p> <p>In $\ce{BH_{4}^{-}}$ ...
213
oxidation states
Why do heavier transition metals show higher oxidation states?
https://chemistry.stackexchange.com/questions/67510/why-do-heavier-transition-metals-show-higher-oxidation-states
<p>In p-block elements, higher oxidation states are less stable down the group due to the inert pair effect. This is not the case for transition metals.</p> <p>Why do heavier transition metals show higher oxidation states than lighter ones? Is the inert pair effect not valid for transition metals also?</p>
<p>The inert pair effect is based on the fact that main group elements’ oxidation states depend on s and p orbitals (and only them). When going down the periodic table, the energy difference between s and p orbitals changes leading to some elements losing their valence s electrons more easily than others.</p> <p>Trans...
214
oxidation states
Comparing the number of oxidation states of Vanadium and Arsenic
https://chemistry.stackexchange.com/questions/107718/comparing-the-number-of-oxidation-states-of-vanadium-and-arsenic
<p>USNCO 2004 Question 45 states:</p> <blockquote> <p>Which element exhibits the greatest number of oxidation states in its compounds?</p> <p>(A) Ca (B) V (C) Cu (D) As</p> </blockquote> <p>I ruled out Ca, as I know it only exists as +2. I then drew electron configurations for V, Cu and As. I ruled out Cu as...
215
oxidation states
How does one calculate oxidation states?
https://chemistry.stackexchange.com/questions/129501/how-does-one-calculate-oxidation-states
<p>For example, how could I calculate the oxidation state of lead in <span class="math-container">$\ce{PbS}$</span>? Or for that matter how would I calculate it for sulfur? Or I have two unknowns, for example sulfur in <span class="math-container">$\ce{PbSO4}$</span>? Do I assume that lead has a 2+ charge and therefore...
<p>For compounds where you have a non-metal with a metal, there is likely an ionic bond. The oxidation states are just the charges on the ion. PbS has Pb2+ and S2-, so those charges are simply the oxidation states.</p> <p>For PbSO4, you know sulfate is a 2- ion, so it must be bonded to a Pb2+. Therefore, again, Pb has...
216
oxidation states
Why do negative oxidation states not extend to -8?
https://chemistry.stackexchange.com/questions/15337/why-do-negative-oxidation-states-not-extend-to-8
<p>There are oxidation states from -4 to +8</p> <p>Why do the negative oxidation states not go all the way down to -8? I mean if an atom is hypervalent meaning that it can have more than an octet than that means it can have potentially 8 bonds(counting a double bond as 2 bonds and a triple bond as 3 bonds respectively...
<blockquote> <p>Why do the negative oxidation states not go all the way down to -8?</p> </blockquote> <p>Let's think about what we would need for this to occur - i.e. an oxidation state of -8.</p> <p>We would need a central atom that has considerable electronegativity - one that is at least more electronegative tha...
217
oxidation states
Why are fluorides of transition metals unstable in low oxidation states?
https://chemistry.stackexchange.com/questions/55778/why-are-fluorides-of-transition-metals-unstable-in-low-oxidation-states
<p>Why are fluorides of transition metals unstable in low oxidation states? </p> <p>I would think that since fluorine and oxygen are highly electronegative, it's obvious that they be stable at high oxidation states. However, $\ce{Cl}$ is also highly electronegative, but it does exist in low oxidation states with tra...
<p>You can take the example of $\ce{CuF}$ which is not known.</p> <p>Reason: $\ce F$ is such an electronegative element that it will always oxidise $ \ce{Cu}$ to $\ce{Cu^2+}$ and not $\ce{Cu^1+}$. Hence, whenever $\ce{Cu}$ reacts with flourine, copper(II) flouride is formed. The following reaction illustrates this:</p...
218
oxidation states
Electronegativity Considerations in Assigning Oxidation States
https://chemistry.stackexchange.com/questions/10944/electronegativity-considerations-in-assigning-oxidation-states
<p>I have never seen anything other than a set of rules like these when textbooks present how to assign oxidation numbers. Such as these: </p> <p><img src="https://i.sstatic.net/YlxeX.png" alt="enter image description here"></p> <p>However, if we keep in mind that oxidation numbers are simply imaginary numbers which ...
<p>In the IUPAC Recommendations 2016 the definition of oxidation state underwent a significant and comprehensive change. It does now resemble the version wich was proposed be Hans-Peter Loock and is quoted in the earlier version of this answer, parts of which are included below.</p> <p>The electronegativity battle sche...
219
oxidation states
Balancing redox equations with oxygens in multiple oxidation states
https://chemistry.stackexchange.com/questions/129467/balancing-redox-equations-with-oxygens-in-multiple-oxidation-states
<p>How do you balance this using the ion-electron method;</p> <p><span class="math-container">$\ce{CrO5 + H2SO4 -&gt; Cr2(SO4)3 + H2O + O2}$</span></p> <p>The oxygen has multiple oxidation states in <span class="math-container">$\ce{CrO5}$</span>, and none of the sites I looked this up on dealt with that.</p>
<p>This is a rather unusual case of what is discussed in answers like <a href="https://chemistry.stackexchange.com/a/91664/17175">this one</a>, where we circumvent problems with multiple atoms being oxidized or reduced by considering whole compounds as oxidizing or reducing agents.</p> <p>Here, the whole-compound redo...
220
oxidation states
Can you write oxidation states with negative Roman numerals?
https://chemistry.stackexchange.com/questions/171876/can-you-write-oxidation-states-with-negative-roman-numerals
<p>As I understand, Roman numerals are used for oxidation states, whereas Arabic numerals are used for the charge of full ions, with some ambiguity allowed when a metal centre is all but ionised, such as in hexaaqua compounds.</p> <p>But I have never seen a Roman numeral with a negative sign in front of it. Would I wr...
<p>According to IUPAC guidelines, roman numerals are used to denote oxidation states when used in the name of a compound. This is used when the cationic group can have varying oxidation states. For example, <span class="math-container">$\ce{FeSO4}$</span> is written as iron (II) sulphate, and <span class="math-containe...
221
oxidation states
Reactivity of Ni Vs. Pd - available oxidation states
https://chemistry.stackexchange.com/questions/111829/reactivity-of-ni-vs-pd-available-oxidation-states
<p>I'm hoping someone can help me tighten up my understanding of the origins of the differences between Ni and Pd catalysis. </p> <p>I understand that Ni has higher charge density and this is the reason for it's larger capacity for oxidative addition for say an aryl halide. It also has access to the oxidtaion states (...
222
oxidation states
What are the oxidation states of sulfur in the tetrathionate ion?
https://chemistry.stackexchange.com/questions/5643/what-are-the-oxidation-states-of-sulfur-in-the-tetrathionate-ion
<p>What are the oxidation states of the sulfur in the tetrathionate ion <span class="math-container">$\ce{S4O6^{2-}}$</span>?</p> <p><a href="https://i.sstatic.net/l5kDW.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/l5kDW.png" alt="Structure"></a></p>
<p>Consider the structure of <a href="http://en.wikipedia.org/wiki/Tetrathionate">tetrathionate</a>. The two central sulfurs each have two lone pairs and are assigned half of the electrons from the two bonds they make, since the electrons of bonds between atoms of the same element must be distributed evenly (due to the...
223
oxidation states
why oxidation states of suphur atoms of Disuphur-monoxide is +2 and 0?
https://chemistry.stackexchange.com/questions/71924/why-oxidation-states-of-suphur-atoms-of-disuphur-monoxide-is-2-and-0
<p><a href="https://i.sstatic.net/Szzjs.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Szzjs.jpg" alt="enter image description here"></a></p> <p>I) According to my logic, sulfur-sulfur linkage (linkage between same atoms) result in no charge separation.So, the oxidation number of the sulfur atom linked...
224
oxidation states
Difference in the change in oxidation states of transition elements and p-block elements
https://chemistry.stackexchange.com/questions/44220/difference-in-the-change-in-oxidation-states-of-transition-elements-and-p-block
<p>In transition elements the oxidation states differ by one (+2 to +7 in Mn). However, in the p-block elements, the oxidation states differ by two (-1,+1,+3,+5 in the halogen group). Why is this so?</p>
<p>In d block, variable valency occurs due to small differences in successive ionization enthalpy. Hence, it shows valency with difference of 1</p> <p>While in p block, variable valency occurs due to inert pair effect. Due to this 2 electrons remain paired and become inert for bonding. Hence, in p block the difference ...
225
oxidation states
Why middle elements of transition series show more number of oxidation states
https://chemistry.stackexchange.com/questions/168510/why-middle-elements-of-transition-series-show-more-number-of-oxidation-states
<p>Why do the elements in the middle of the transition series show more number of common oxidation states than others?</p> <p><img src="https://2.bp.blogspot.com/-gl6AodOkf5c/VLPvPFYxBPI/AAAAAAAAA1M/YFFFFmXKHU0/s1600/variable-oxidation-states-of-transition-elements.JPG" alt="" /></p>
226
oxidation states
Why do osmium and iridium have the most oxidation states of all the elements?
https://chemistry.stackexchange.com/questions/61353/why-do-osmium-and-iridium-have-the-most-oxidation-states-of-all-the-elements
<p>Both osmium and iridium have 12 oxidation states. Indeed, iridium has the highest oxidation state of all elements at +9. see <a href="https://en.wikipedia.org/wiki/List_of_oxidation_states_of_the_elements" rel="nofollow">https://en.wikipedia.org/wiki/List_of_oxidation_states_of_the_elements</a></p> <p>I'm just cu...
227
oxidation states
Why are oxidation states such a fundamental quantity for elements?
https://chemistry.stackexchange.com/questions/70463/why-are-oxidation-states-such-a-fundamental-quantity-for-elements
<blockquote> <p>Why is it that there are fixed oxidation states for most elements out there, with no to very rare exceptions? </p> </blockquote> <p>I was taught that oxidation state is a totally artificial concept we have invented for book-keeping purposes. How is it that its applicable so widely? I understand the c...
228
oxidation states
Which oxidation states were used when Pauling developed his electronegativity scale?
https://chemistry.stackexchange.com/questions/151759/which-oxidation-states-were-used-when-pauling-developed-his-electronegativity-sc
<p>Paulings electronegativity is a relative scale, based on the difference in electronegativity between X and Y, <span class="math-container">$\Delta EN = 0.102 \sqrt {\Delta}$</span>, where <span class="math-container">$\Delta = (X-Y)_{measured}-(X-Y)_{theoretical}$</span> bond energies.</p> <p>But what is the oxidati...
229
oxidation states
Can an element have variable oxidation states in a compound?
https://chemistry.stackexchange.com/questions/111748/can-an-element-have-variable-oxidation-states-in-a-compound
<p>Take propanoic acid for example. If I assign oxidation states to the 3 carbons in it using the idea that the more electronegative element gets all the electrons in the bonds it makes, the 3 carbons get -3( the one in the CH3), -2( the one in the middle), and +3( the one in the acid group). </p> <p>Is this conclusio...
230
oxidation states
How are oxidation states of bioinorganic molybdenum/tungsten complexes determined?
https://chemistry.stackexchange.com/questions/180636/how-are-oxidation-states-of-bioinorganic-molybdenum-tungsten-complexes-determine
<p>Here a screenshot from our lecture on bioinorganic molybdenum complexes, dealing with the catalytic cycle of xanthine oxidase:</p> <p><a href="https://i.sstatic.net/oSChf.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/oSChf.png" alt="enter image description here" /></a></p> <p>It is said that the onl...
231
oxidation states
Oxidation states of boron
https://chemistry.stackexchange.com/questions/108521/oxidation-states-of-boron
<p>I have just been looking at <a href="https://en.wikipedia.org/wiki/List_of_oxidation_states_of_the_elements" rel="nofollow noreferrer">https://en.wikipedia.org/wiki/List_of_oxidation_states_of_the_elements</a> and found that boron has a -5 oxidation state. I would like to know which boron compounds form this ox...
<p>As I remember I have read somewhere that <span class="math-container">$\ce{Al3BC}$</span> is konwn to have Boron in -5 oxidation state. </p> <ul> <li>you can also reffer to this PDF page no. 139 <a href="https://d-nb.info/995006210/34" rel="nofollow noreferrer">PDF IN GERMAN</a></li> </ul>
232
oxidation states
Oxidation states of iron in Roussin&#39;s salts
https://chemistry.stackexchange.com/questions/53588/oxidation-states-of-iron-in-roussins-salts
<blockquote> <p>For preservation of meat, sodium nitrite is usually added and as a result <span class="math-container">$\ce{NO}$</span> is then formed. Consequently, <span class="math-container">$\ce{NO}$</span> reacts with the sulfur and iron atoms from decomposition of proteins, forming <span class="math-container"...
<p>I suppose it's asked about formal oxidation numbers of iron as there is not enough information to make assumptions about the ones that reflect electronic structure. For instance, analysis of interatomic distances could point to a delocalized electron pair, but you are not given any linear or angular geometrical para...
233
oxidation states
Is it possible for halogens to show oxidation states less than -1?
https://chemistry.stackexchange.com/questions/59146/is-it-possible-for-halogens-to-show-oxidation-states-less-than-1
<p>Halogens like $\ce{Cl,Br,I}$ generally show oxidation states between $-1$ and $+7$. However, is it possible that they can show an oxidation state beyond $-1$ (e.g. $-3$)?</p> <p>I was thinking of some compound in which chlorine is bonded with a less electronegative element and forms more than one bond with such ele...
<p>Yes, they can show oxidation states lower than -1. For example in <a href="http://onlinelibrary.wiley.com/doi/10.1002/rcm.2712/abstract">hyperlithiated compounds</a>, like $\ce{Li3Cl}$, the chlorine would formally have an oxidation state of -3.</p> <p>However, a word of caution, oxidation states are a tricky thing....
234
oxidation states
Oxidation States of Actinides
https://chemistry.stackexchange.com/questions/82722/oxidation-states-of-actinides
<p>It is observed that actinides do not exhibit +2 oxidation state, contrary to that of some of the lanthanide elements. Why?</p>
<p>See also: <a href="https://chemistry.stackexchange.com/q/48971/16683">Why is WF6 stable whereas CrF6 is unknown?</a></p> <p>Whenever one wants to compare oxidation states, there are a couple main factors to take into account. To reach a <em>higher</em> oxidation state, one obviously has to pay for it in the form of...
235
oxidation states
Stability of 3d metal fluorides and iodides in different oxidation states
https://chemistry.stackexchange.com/questions/102326/stability-of-3d-metal-fluorides-and-iodides-in-different-oxidation-states
<p>I read that the fluorides of 3d metals in lower oxidation states, e.g. <span class="math-container">$\ce{VF2}$</span>, <span class="math-container">$\ce{TiF2}$</span>, and <span class="math-container">$\ce{CuF}$</span> are thermodynamically unstable. For example, <span class="math-container">$\ce{CuF}$</span> dispro...
<p>In general, iodides stabilise lower oxidation states and fluorides stabilise higher oxidation states, e.g. <span class="math-container">$\ce{CuF2}$</span> versus <span class="math-container">$\ce{CuI}$</span>. This can be explained with some thermodynamics. Consider</p> <p><span class="math-container">$$\ce{M(s) + ...
236
oxidation states
Reference for electronegativities of different metal oxidation states
https://chemistry.stackexchange.com/questions/115469/reference-for-electronegativities-of-different-metal-oxidation-states
<p>A long time ago I was researching the effect of the self regulatory response in Fe and Co. I found that my results made sense based on the idea of the electronegativity of the ions considered. I found a webpage that listed the relationship between the different electronegativities for different oxidation states of ...
<p>Pearson conveniently lists cumulative experimental data in the 1988 paper [<a href="https://doi.org/10.1021/ic00277a030" rel="noreferrer">1</a>], referrring to the earlier work of Moore [2]. Selected values of <span class="math-container">$I$</span> (ionization potential), <span class="math-container">$A$</span> (el...
237
oxidation states
Are fractional oxidation states possible?
https://chemistry.stackexchange.com/questions/5357/are-fractional-oxidation-states-possible
<p>To get the oxidation state of carbon (denoted $x$) in octane, $\ce{C8H18}$, I used the fact that hydrogen has an oxidation state of $+1$:</p> <p>$$8x + 18\cdot 1 = 0 \qquad \Longrightarrow \qquad x = -\frac{18}{8} = -2.25$$</p> <p>But in that way, I get an oxidation number that is fractional, or not an integer. Is...
<p>The "oxidation number" is a theoretical value used to do electron bookkeeping and is one way of comparing the number of electrons "owned" by an atom in a molecule or ion versus how many valence electrons present in the atom as depicted on the periodic table.</p> <p>Your calculation is assuming that all of the carbo...
238
oxidation states
How to determine the oxidation states of the metal atoms when both cation and anion are coordination complexes?
https://chemistry.stackexchange.com/questions/59089/how-to-determine-the-oxidation-states-of-the-metal-atoms-when-both-cation-and-an
<p>How to determine the oxidation states of the metal atoms when both cation and anion are coordination complexes?</p> <p>For example, how to determine the oxidation states of <span class="math-container">$\ce{Pt}$</span> in the following compound?:</p> <p><span class="math-container">$[\ce{Pt(NH3)4}][\ce{PtCl6}]$</s...
<p>There is something called an average oxidation state, which is typically not very meaningful chemically, but can (usually) easily be calculated by just knowing the structural formula. In your case, since chlorine is the most electronegative element (save nitrogen), you can assume it to be in $\mathrm{-I}$ state whil...
239
oxidation states
What are the magnetic properties of [Ni(S2C2Ph2)2]^z&#39;s 3 oxidation states?
https://chemistry.stackexchange.com/questions/91903/what-are-the-magnetic-properties-of-nis2c2ph22zs-3-oxidation-states
<p><a href="https://i.sstatic.net/je5ua.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/je5ua.png" alt="enter image description here"></a></p> <p>I was doing some research on Wikipedia and I came across the article on <a href="https://en.wikipedia.org/wiki/Non-innocent_ligand" rel="nofollow noreferrer">...
<p>$\ce{Ni^{2+}}$ is a $d^8$ metal. In a square planar orbital splitting, all $8$ electrons are paired, hence it is diamagnetic. Even when the complex is neutral, the electron loss is at the ligands (by definition, non-innocent), and they are antiferromagnetically coupled, which means that their spins "cancel" each oth...
240
oxidation states
Do different oxidation states of the same element have the same emission spectrum?
https://chemistry.stackexchange.com/questions/119671/do-different-oxidation-states-of-the-same-element-have-the-same-emission-spectru
<p>I looked at the flames of copper (I) chloride and of copper (II) chloride through a spectroscope and they looked the same. The flame colour is the same too. But since they have different oxidation states, and therefore different electron configurations, should their emission spectra be slightly different?</p> <p>Wo...
<p>Interesting question. Keep in mind that the elemental emission spectrum in a flame or plasma and even a discharge does not remember its history in solution or a solid phase.</p> <p>The punchline is that the emission spectrum is dependent on the elements <em>gas phase chemistry</em> in the flame/plasma/discharge. Pr...
241
oxidation states
Are such high oxidation states as reported by Vojovodic et al. possible?
https://chemistry.stackexchange.com/questions/99065/are-such-high-oxidation-states-as-reported-by-vojovodic-et-al-possible
<p>I am a student in theoretical chemistry and I am confused about the paper: Trends in adsorption of electrocatalytic water splitting intermediates on cubic $\ce{ABO3}$ oxides (Montoya, J. H.; Doyle, A. D.; Nørskov, J. K.; Vojvodic, A.; <em>Phys. Chem. Chem. Phys.</em> <strong>2018,</strong> <em>20</em> (5), 3813–3818...
<p>Oxidation states are just numbers, a bookkeeping tool for chemistry. These hardly ever correspond to anything observable. Point in case: hypofluorous acid $\ce{HOF}$, see for example <a href="https://chemistry.stackexchange.com/q/15579/4945">the oxidation state of oxygen</a> and <a href="https://chemistry.stackexcha...
242
oxidation states
why heavier transition metals can stabilise higher oxidations states
https://chemistry.stackexchange.com/questions/139680/why-heavier-transition-metals-can-stabilise-higher-oxidations-states
<p>I believe similar questions have been asked but this is different and the answers I have looked at don't answer this question. I have read that oxidation states of heavier transition elements (Ru, Os etc) are more <strong>stable</strong> than first row transition metals.</p> <p>I understand how they can get to the o...
243
oxidation states
Why is silver considered a &quot;type 1&quot; metal although it has multiple oxidation states?
https://chemistry.stackexchange.com/questions/167988/why-is-silver-considered-a-type-1-metal-although-it-has-multiple-oxidation-sta
<p>I noticed that the metals I learned were &quot;type 1&quot; back in early chemistry class as they have one oxidation state including silver, aluminum, zinc, and cadmium. However, those metals weren't reported as &quot;type 1&quot; when I looked online. I noticed that although silver has three oxidative states, it is...
<p>I haven't heard of this classification of metals before. Anyways, the below image is from <a href="https://www.amherst.edu/media/view/226859/original/Chem11%2B1011F%2BD1%2BNomenclature%2Bhandout.pdf" rel="nofollow noreferrer">a nomenclature handout</a> where silver has been considered &quot;type 2&quot; metal:</p> <...
244
oxidation states
Is there an error in a Wikipedia article explaining the influence of oxidation states?
https://chemistry.stackexchange.com/questions/136697/is-there-an-error-in-a-wikipedia-article-explaining-the-influence-of-oxidation-s
<p>Referring to the series of oxoacids of chlorine: <span class="math-container">$\ce{HClO, HClO2, HClO3},$</span> and <span class="math-container">$\ce{HClO4}$</span>, tabulated in <a href="https://en.wikipedia.org/wiki/Electronegativity#Variation_of_electronegativity_with_oxidation_number" rel="nofollow noreferrer">t...
<p>Please do not edit the Wikipedia article, as your wording is incorrect, and the existing wording, while awkward, is correct.</p> <p>What the article is trying to say is that the electron density on <em>each oxygen</em> is less as the oxidation state of the Cl increases. We can understand this by imagining progressiv...
245
oxidation states
Oxidation states the elements in nitrosyl chloride
https://chemistry.stackexchange.com/questions/127893/oxidation-states-the-elements-in-nitrosyl-chloride
<p>I have read that <span class="math-container">$\ce{NOCl}$</span> dissociates to <span class="math-container">$\ce{NO+}$</span> and <span class="math-container">$\ce{Cl-},$</span> and the various reasons stated as such seem fine.</p> <p>But what I don't get is this: if we follow the actual rules of assigning oxidati...
246
oxidation states
Manganese Oxidation States, Reverse Chameleon?
https://chemistry.stackexchange.com/questions/181885/manganese-oxidation-states-reverse-chameleon
<p>A well known experiment is where a basic sodium hydroxide and sucrose solution is added to a KMnO4 solution. The colors change from purple permanganate to green manganate to yellow/orange manganese dioxide (sometimes blue hypomanganate is formed as an intermediate). This common demo is called the 'Chemical Chameleon...
<p>Probably your best approach is to use the methods reported by <a href="https://en.wikipedia.org/wiki/Potassium_permanganate" rel="nofollow noreferrer">Wikipedia</a>. The most commonly used method in industry involves these steps:</p> <ul> <li><p>Dissolve solid <span class="math-container">$\ce{MnO2}$</span> in molte...
247
oxidation states
Why Scandium (Sc) doesn&#39;t show variable oxidation states (especially +2), while other transition elements show variable oxidation states?
https://chemistry.stackexchange.com/questions/167718/why-scandium-sc-doesnt-show-variable-oxidation-states-especially-2-while
<p>I have read answer to this question on various sites, but was not satisfied by the answers, because I am not able to understand, that if we remove initially 1 electron from scandium, then 4s would be ome unstable, but if we remove 1 more electron, there remains only one electron in 3d subshell. But we have already o...
<p>The claim that the second ionization energy of scandium far exceeds the first is simply not true, or as least not specifically true of scandium. A quick look at the <a href="https://en.wikipedia.org/wiki/Scandium" rel="nofollow noreferrer">Wikipedia page</a> reveals that the first ionization energy is 633 kJ/mol and...
248
oxidation states
Explanation for increase in the number of oxidation states for transition elements from Sc to Mn of the 4th period
https://chemistry.stackexchange.com/questions/14539/explanation-for-increase-in-the-number-of-oxidation-states-for-transition-elemen
<p>From Sc, to Mn, the number of oxidation states increases from one (Sc) to seven (Mn). The explanation for this is because the unpaired 3d electrons can be lost along with the 4s electrons during bonding.</p> <p>Should this be the case? Wouldn't it be easier to lose an electron when it is paired because of interelec...
<p>The oxidation state of a transition metal is an accounting device. It's not the number of "lost electrons". In potassium permanganate, which has Mn (VII), the manganese atom shares its seven 3d electrons with the ligand (oxygen) in what are essentially covalent bonds, and the "positive charge" associated with the ...
249
electrochemistry
Effect of passing hydrogen sulfide gas on electrode potential
https://chemistry.stackexchange.com/questions/49640/effect-of-passing-hydrogen-sulfide-gas-on-electrode-potential
<blockquote> <p>Consider the cell reaction</p> <p><span class="math-container">$$\ce{2Ag+ + Pb &lt;=&gt; 2Ag + Pb^2+}$$</span> If <span class="math-container">$\ce{H2S}$</span> gas is passed through the solution, what will be the effect on the EMF of the cell?</p> </blockquote> <p><strong>My attempt:</strong></p> <p>Th...
250
electrochemistry
How to calculate the electromotive force of a silver chloride/ silver bromide cell?
https://chemistry.stackexchange.com/questions/59383/how-to-calculate-the-electromotive-force-of-a-silver-chloride-silver-bromide-ce
<blockquote> <p>For the galvanic cell: $\ce{Ag|AgCl(s)|KCl(0.2M)||KBr(0.001M)|AgBr(s)|Ag}$, calculate the electromotive force (EMF) generated.<br> $K_\mathrm{sp}(\ce{AgCl}) = 2.8\times10^{-10}$; $K_\mathrm{sp}(\ce{AgBr}) = 3.3\times10^{-13}$</p> </blockquote> <p>I have tried this forming the cell reaction which...
<p><span class="math-container">$$\begin{align} E_{\ce{Ag/AgBr}}&amp;=E_{\ce{Ag/Ag+}}^{\circ}+0.059\log\frac{K_{\rm sp, AgBr}}{[\ce{Br-}]} \\ E_{\ce{Ag/AgCl}}&amp;=E_{\ce{Ag/Ag+}}^{\circ}+0.059\log\frac{K_{\rm sp, AgCl}}{[\ce{Cl-}]} \\ EMF&amp;=0.059 \cdot \left| \log \left( {\frac { K_{\rm sp, AgCl} \cdot [\ce{Br-}]...
251
electrochemistry
Cell notation for the lead-acid battery
https://chemistry.stackexchange.com/questions/89562/cell-notation-for-the-lead-acid-battery
<p>Reactions for the lead acid battery are: </p> <p><span class="math-container">$$ \begin{array}{} \text{Oxidation}&amp;\ce {Pb(s) + HSO4^-(l) &amp;-&gt; PbSO4(s) + H+(l) + 2e-}\\ \text{Reduction}&amp;\ce{PbO2 + HSO4^-(l) + 3H+(l) + 2e- &amp;-&gt; PbSO4(s) + 2H2O}\\ \text{Total reaction}&amp;\ce{Pb(s) + PbO2(s) +2HSO...
<p>There are a couple of things wrong here. First off, your final reaction is <strong>unbalanced</strong>. Once you've fixed the balancing, read the other mistakes:</p> <ol> <li>The ions do not exist in the <strong>liquid</strong> state! They are solvated/hydrated by the solvent. Since the solvent is water here, we'll...
252
electrochemistry
Role of potassium hydroxide in alkaline battery?
https://chemistry.stackexchange.com/questions/135351/role-of-potassium-hydroxide-in-alkaline-battery
<p>Is the role of potassium hydroxide (<span class="math-container">$\ce{KOH}$</span>) in an alkaline battery to provide hydroxide for the reaction with zinc? Would the battery cease to work if <span class="math-container">$\ce{KOH}$</span> was removed and only <span class="math-container">$\ce{OH-}$</span> from autoio...
<p>The role of <span class="math-container">$\ce{KOH}$</span> is to provide enough ions for redox reactions. Remember that redox reactions come in pairs, for every reduction there must be oxidation. If <span class="math-container">$\ce{Zn}$</span> reacts with <span class="math-container">$\ce{OH-}$</span> to form a hyd...
253
electrochemistry
Are electrostatic effects temperature dependent?
https://chemistry.stackexchange.com/questions/135373/are-electrostatic-effects-temperature-dependent
<p>A charged particle like an ion, does its repulsive or attractive effect on other particles change with temperature? Are electrostatic effects temperature dependent?</p>
<p>The strength of the electric charge does <em>not</em> change with temperature (unless approaching that of the Big Bang). However, <em>effects</em> of the charges do change with temperature. For example, at low temperatures (near 0 K), <a href="https://phys.org/news/2020-06-arrays-strontium-rydberg-atoms-quantum.html...
254
electrochemistry
Current with an ionic solution
https://chemistry.stackexchange.com/questions/135389/current-with-an-ionic-solution
<p>For the last assignment of the school year, my science teacher gave the class questions about chem, physics, etc. The third question had me confused and I'll be thankful for all the help given. The question is:</p> <blockquote> <p>An ionic solution is created and tested to see how much current can go through it. Two...
<p>No offence to you (certainly to the original author of this question), I call such home-work questions such as garbage in-garbage out type questions. No wonder a student will be confused if they see such open ended questions. The reason is that the author is not telling you or us of 2.0 grams of what?</p> <p>Even if...
255
electrochemistry
Can I use activated carbon electrod as a reference electrod in a pH meter instead of using murcury?
https://chemistry.stackexchange.com/questions/139774/can-i-use-activated-carbon-electrod-as-a-reference-electrod-in-a-ph-meter-instea
<p>Activated carbon is less expensive than mercury . They are recyclable . Mercury is toxic. Nowadays activated carbon is being used in supercapacitors,Li-ion battery.</p>
<p>Reference electrodes must involve a well defined redox system with reproducible potential.</p> <p>Mercury is an essential part of the redox system of the calomel reference electrode <span class="math-container">$\ce{Hg|Hg2Cl2(s)|Cl-}$</span>: <span class="math-container">$$\ce{2 Hg &lt;=&gt; Hg2^2+ + 2 e-}$$</span> ...
256
electrochemistry
How does solution which electrodes are immersed in effect electrode potential?
https://chemistry.stackexchange.com/questions/123539/how-does-solution-which-electrodes-are-immersed-in-effect-electrode-potential
<p>When we make an electrochemical cell, we dip the electrodes in the salt solution. How exactly does the electrode potential change as we dip the electrodes in the salt solutions? Would different salt solutions change the effect of the electrode potential?</p>
<p>The short answer is that we want a cathodic reaction so we can use the metals with a positive standard reduction potential (because 0 is for <span class="math-container">$\ce{H2} $</span> reduction).</p> <p>In reality however to really find a suitable electrolyte cyclic voltammetry is typically used and electrolyte...
257
electrochemistry
What is the relationship between the stability constant of a copper (II) electrolyte complex ion and the output voltage Ecell?
https://chemistry.stackexchange.com/questions/141116/what-is-the-relationship-between-the-stability-constant-of-a-copper-ii-electro
<p>As a part of a school investigation I constructed a voltaic cell experiment where for each run I added a different ligands to the copper (II) sulfate half-cell electrolyte in a daniell cell to see if there was a change in the output voltage Ecell. When plotting a graph of this, it seemed that Ecell increased as the ...
<p>The redox potential of Copper does not depend directly on the stability of the complex Cu-ligand. It depends on the concentration of the residual <span class="math-container">$\ce{Cu^{2+}}$</span> ion in solution. And in any solution of <span class="math-container">$\ce{CuSO4}$</span>, adding a ligand produces a dec...
258
electrochemistry
How to derive the Henderson equation for liquid junction potentials given in Bard and Falkner?
https://chemistry.stackexchange.com/questions/142862/how-to-derive-the-henderson-equation-for-liquid-junction-potentials-given-in-bar
<p>The general equation for liquid junction potential is given by <span class="math-container">$$E = {-RT\over F}\sum_i\int_a^b{t_i\over z_i}d ln(a_i)$$</span> Where a and b are the two phases, <span class="math-container">$t_i$</span> is the transport number of the ions and <span class="math-container">$z_i$</span> is...
259
electrochemistry
How long do rechargeable Batteries last vs Standard Batteries?
https://chemistry.stackexchange.com/questions/143664/how-long-do-rechargeable-batteries-last-vs-standard-batteries
<p>Ordinary Batteries will deplete most of their Power in a 10 year period. What happens to rechargeable Batteries? How long would they still functin properly?</p> <p>Hope this is the right community for this question. If you need a specific example:</p> <p>Powertoll Battery: <a href="https://www.metabo.com/ch/de/zubeh...
<p>It mostly depend on battery type, and after that current. Batteries usually dislike very high currents, that would make them charge or discharge faster than in 1 hour, because of heating and secondary reactions, and very low currents, that would make them discharge in a year, because of dendrite formation.</p> <p>Wo...
260
electrochemistry
Why does lower concentration cause the metal atoms to dissipate more?
https://chemistry.stackexchange.com/questions/145201/why-does-lower-concentration-cause-the-metal-atoms-to-dissipate-more
<p>In a <a href="https://en.wikipedia.org/wiki/Concentration_cell" rel="nofollow noreferrer">concentration cell</a>, one can measure a voltage because in one of the half cells (the one with lower concentration electrolyte), the atoms tend to dissipate more into the electrolyte as ions, leaving more electrons behind (co...
<p>It is not primarily that the process <span class="math-container">$\ce{M(s) -&gt; M^n+(aq) + n e-}$</span> is faster for more diluted solutions.</p> <p>The main reason is that the opposite process <span class="math-container">$\ce{M^n+(aq) + n e- -&gt; M(s)}$</span> is slower for more diluted solutions.</p> <p>As th...
261