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reaction kinetics | Finding the rate of a reaction given experimental data for reaction kinetics | https://chemistry.stackexchange.com/questions/152863/finding-the-rate-of-a-reaction-given-experimental-data-for-reaction-kinetics | <p>Here is the question:</p>
<blockquote>
<p>For the reaction:
<span class="math-container">$$\ce{2 A + 2 B → C + D}$$</span></p>
<p>The following data was obtained from three experiments:
<span class="math-container">\begin{array}{c|ccc}\hline
\bf{Experiment} &\textbf{[A] (mol/L)} &\textbf{[B] (mol/L)} &... | <p>As I said in the comments, your image is quite low resolution. But, if I read it correctly, you have got the exponents in the rate law wrong.</p>
<p>Solving this type of problem is simple, you just need to check if the rate law makes intuitive sense. The data given in the question contains various instantaneous rate... | 362 |
reaction kinetics | Special case of Cannizaro reaction of formaldehyde with 100% NaOH/KOH follows 4th order kinetics | https://chemistry.stackexchange.com/questions/88145/special-case-of-cannizaro-reaction-of-formaldehyde-with-100-naoh-koh-follows-4t | <p>It is given that when we use $50{-}\pu{60\%}\ \ce{KOH}$ in a Cannizaro reaction of formaldehyde, the reaction follows third order kinetics, but under special cases of Cannizaro reactions it was given than when formaldehyde reacts with $\pu{100\%}\ \ce{NaOH/KOH}$ the reaction follows fourth order kinetics.</p>
<p>Wh... | 363 | |
reaction kinetics | Kinetics of Sabatier reaction | https://chemistry.stackexchange.com/questions/136134/kinetics-of-sabatier-reaction | <p>I am modelling a methanation process in MATLAB, where I have a rate equation for methanation</p>
<p><span class="math-container">$$\ce{CO2 + 4 H2 → CH4 + 2 H2O}$$</span></p>
<p>in which I need partial pressure of <span class="math-container">$\ce{CO2},$</span> <span class="math-container">$\ce{H2},$</span> <span cla... | <p>So you need three things:</p>
<ol>
<li>Partial pressures of species.</li>
<li>Amount of catalyst.</li>
<li>Reactor volume.</li>
</ol>
<p>We will design a PBR in order to calculate the mass of catalyst <span class="math-container">$ W $</span> needed to achieve a certain conversion <span class="math-container">$ X $<... | 364 |
reaction kinetics | Chemical kinetics of a reaction, rate constant, and activation energy | https://chemistry.stackexchange.com/questions/43576/chemical-kinetics-of-a-reaction-rate-constant-and-activation-energy | <p>From the Arrhenius equation in kinetics of reactions,</p>
<p>$$k = A\exp{\left(-\frac{E_\mathrm{a}}{RT}\right)}$$</p>
<p>Which tells us about <strong>the temperature dependence on rate constant of a reaction.</strong></p>
<p><strong>Activation energy is dependent on the temperature</strong> (as it is the energy d... | <p>The rate constant and the activation energy tell us how fast the reaction proceeds (moles/sec), not whether it is spontaneous. The higher the temperature, the higher the rate constant and, for specified concentrations of reactants, the faster the reaction. The rate of a reaction always increases with increasing temp... | 365 |
reaction kinetics | Chemical Kinetics(Hypothetical elementary reaction) | https://chemistry.stackexchange.com/questions/125824/chemical-kineticshypothetical-elementary-reaction | <p><a href="https://i.sstatic.net/mrjg4.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/mrjg4.jpg" alt="So this is the question, hope someone can help."></a></p>
<p>For a hypothetical elementary reaction(image).
Initially, only 2 moles of A are present. The total number of moles of A, B, and C at the en... | <p><span class="math-container">$75$</span>% of <span class="math-container">$2$</span> moles of A is <span class="math-container">$1.5$</span> mole. <span class="math-container">$1,5$</span> mol A produce twice as much of B or C. This makes <span class="math-container">$3$</span> mol of B and/or C. It remains <span cl... | 366 |
reaction kinetics | Kinetics of the thiosulfate and hydrochloric acid reaction | https://chemistry.stackexchange.com/questions/188374/kinetics-of-the-thiosulfate-and-hydrochloric-acid-reaction | <p>As an exercise in chemistry, I decided to observe the kinetics of the decay of thiosulfate ions in an acidic medium. As far as I am aware, it is a very well known exercise among chemists.</p>
<p>I found a paper in which the author uses a sodium thiosulfate solution with a concentration of 0.25 mol/L and sulfuric aci... | 367 | |
reaction kinetics | How to make sense of the 'Relaxation Method' for measuring reaction kinetics? | https://chemistry.stackexchange.com/questions/24416/how-to-make-sense-of-the-relaxation-method-for-measuring-reaction-kinetics | <p>I get the concept that one can measure the rate of reaction by measuring the rate at which an equilibrium state reaches another equilibrium state after the system is perturbed (usually by heating). However, I do have an issue with it. Consider the reaction $$\ce{A <=> B}$$ </p>
<p>My lecture handout suggests... | <p>You have two simultaneous reactions, </p>
<p>$$\begin{array}{rcl}
\ce{A} &\xrightarrow{k_1}& \ce{B}\\[6pt]
\ce{B} &\xrightarrow{k_{-1}}& \ce{A}
\end{array}$$</p>
<p>and $\dfrac{\mathrm d[\ce{A}]}{\mathrm dt}$ equals $-k_1 [\ce{A}]$ for the first reaction alone and $k_{-1} [\ce{B}]$ for the second a... | 368 |
reaction kinetics | Kinetics: Order of Reaction | https://chemistry.stackexchange.com/questions/26887/kinetics-order-of-reaction | <p>I am confused as to how an order of a reactant (n or m) in the rate law can be negative. This means that increasing the concentration of a reactant would actually decrease its rate of disappearance. How does this make sense? Doesn't a higher concentration always allow for more collisions? Also, when the order is 0, ... | <p>In principle, <strong><a href="http://chemwiki.ucdavis.edu/Physical_Chemistry/Kinetics/Reaction_Rates/Zero-Order_Reactions" rel="nofollow">there are no zeroth-order reaction</a></strong>. Experimentally, however, zeroth-order rate law occurs because of the reaction condition. For example, in catalytic reactions such... | 369 |
reaction kinetics | Is there a way to find the kinetics data for the strong acid weak base reaction? | https://chemistry.stackexchange.com/questions/34340/is-there-a-way-to-find-the-kinetics-data-for-the-strong-acid-weak-base-reaction | <p>I am layman of chemistry. Latterly, I am asked to do an mathematical optimization task for a bio-chemical process, which contains a conditioning step to neutralize the sulfuric acid using ammonia hydroxide. I am trying to use the mathematical model of the reaction (kinetic model) to optimize the reaction time/energy... | 370 | |
reaction kinetics | Chemical kinetics of a reversible reaction | https://chemistry.stackexchange.com/questions/31047/chemical-kinetics-of-a-reversible-reaction | <p>I am having trouble with the following question:</p>
<blockquote>
<p>Consider the following reversible reaction in which the reaction is first order in both
directions: $$\ce{[A] <=> [B]}$$ $k_\mathrm a$ is the rate constant for the forward reaction and $k_\mathrm b$ is the rate constant for the reverse r... | <p>Third equation looks right to me. That's a <a href="http://pruffle.mit.edu/3.016-2005/Lecture_20_web/node3.html" rel="nofollow noreferrer">non-homogeneous (some would say heterogeneous) first-order differential equation</a>.</p>
<p>I think the heterogeneity is what is giving you problems. Those equations have a g... | 371 |
reaction kinetics | Understanding uni- and termolecular reactions in combustion kinetics | https://chemistry.stackexchange.com/questions/166777/understanding-uni-and-termolecular-reactions-in-combustion-kinetics | <p>I'm trying to understand and incorporate 9-species 19-reaction H2/O2 combustion mechanism into my numerical solver. The reaction mechanism in question is <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/kin.20036" rel="nofollow noreferrer">O'Conaire</a>. It seems that the paper is in some standard chemical-... | 372 | |
reaction kinetics | Kinetics of A + 2 B -> C reaction | https://chemistry.stackexchange.com/questions/86826/kinetics-of-a-2-b-c-reaction | <blockquote>
<p>A reaction $\ce{A + 2 B -> C}$ is carried out in constant volume at $\pu{227 ^\circ C}$. the volume is $\pu{2 L}$. There is no $\ce{C}$ at the beginning. $[\ce{A}]_0 = \pu{0.035 mol L-1}$. $\ce{B}$ concentration changes over time.</p>
<p>\begin{array}{l|cccccccc}
t~(\pu{min})& 0 & 1 &a... | 373 | |
reaction kinetics | Analytical solution for kinetics of bimolecular reaction | https://chemistry.stackexchange.com/questions/83631/analytical-solution-for-kinetics-of-bimolecular-reaction | <p>Consider two chemicals, $\ce{A}$ and $\ce{B}$ that react with each other to make $\ce{C}$ with a reaction rate $k$. The reaction can be expressed as $$\ce{A + B->C}$$ The equation expressing the rate of the reactions can be expressed as $$\frac{d[\ce{A}]}{dt}=\frac{d[\ce{B}]}{dt}=-\frac{d[\ce{C}]}{dt}=-k[\ce{A}][... | <p>Assuming that the <em>bimolecular</em> chemical reaction $\ce{A + B ->[\kappa] C}$ has <a href="https://en.wikipedia.org/wiki/Law_of_mass_action" rel="nofollow noreferrer">mass action</a> kinetics, we have the following pair of coupled ODEs</p>
<p>$$\begin{array}{rl} \dot a &= - \kappa \, a \, b\\ \dot b &am... | 374 |
reaction kinetics | Kinetics vs Thermodynamics | https://chemistry.stackexchange.com/questions/25077/kinetics-vs-thermodynamics | <p>The way kinetics is taught at the undergraduate level (Arrhenius and collision theory) chemical equilibrium is determined governed immensely by activation energy of the reaction. According to thermodynamics, however equilibrium is a function of free energy change. In a way, thermodynamics and kinetics seem to contra... | <p>A great deal of chemistry is determined by the interaction of kinetics and thermodynamics. The world would be a dull place if we didn't have both.</p>
<p>While thermodynamics determines what directions a reaction can go, the kinetics often determines whether the reaction can happen. Take a simple example: diamond i... | 375 |
reaction kinetics | Chemical kinetics for cyclic reversible reaction | https://chemistry.stackexchange.com/questions/168399/chemical-kinetics-for-cyclic-reversible-reaction | <blockquote>
<p>Find <span class="math-container">$[\ce{C}]/[\ce{A}]$</span> for the following system at equilibrium:</p>
<p><a href="https://i.sstatic.net/tY2EA.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/tY2EA.png" alt="Cyclic reversible reaction ABC" /></a></p>
</blockquote>
<p>I know that at equi... | <p>Using the <a href="https://en.wikipedia.org/wiki/Steady_state_(chemistry)" rel="nofollow noreferrer">steady state approximation</a> (SSA), we can obtain the following:</p>
<p><span class="math-container">$$\frac{[\ce{C}]}{[\ce{A}]} = \frac{k_{-2}\frac{[\ce{B}]}{[\ce{A}]} + k_{-3}}{k_2 + k_3} \tag{1}$$</span></p>
<p>... | 376 |
reaction kinetics | Sequential first order reaction graph in chemical kinetics | https://chemistry.stackexchange.com/questions/174588/sequential-first-order-reaction-graph-in-chemical-kinetics | <p>In graph given below is a sequential first order reaction</p>
<p><span class="math-container">$$\ce{A ->[$k_1$] B ->[$k_2$] C}$$</span></p>
<p>For <span class="math-container">$k_2 \gg k_1$</span> the graph of concentration of <span class="math-container">$\ce{A}$</span>, <span class="math-container">$\ce{B}$<... | <p>This question is about the <strong>rate-determining step</strong> of multi-step reactions. Bear in mind that the overall rate of reaction is equal to the slowest step of the reaction, in which case, from <span class="math-container">$\ce{A}$</span> to <span class="math-container">$\ce{B}$</span> (<span class="math-c... | 377 |
reaction kinetics | What guarantees that there is a thermodynamic equilibrium in a closed chemical reaction network independently of the mass-action kinetics? | https://chemistry.stackexchange.com/questions/54519/what-guarantees-that-there-is-a-thermodynamic-equilibrium-in-a-closed-chemical-r | <p>I would like to know according to which we can state that there is a unique equilibrium of a closed chemical reaction network (at constant circumstances) without supposing mass-action kinetics if time is increasing beyond all limits. Can we derive it from a non-equilibrium thermodynamic law or is it a postulate? Tha... | <p>The equilibrium is determined by the thermodynamics, not by the kinetics. The rate constants for the reaction kinetics must be consistent with the equilibrium determined by the thermodynamics. For example, for a single reversible reaction, the reverse reaction rate constant must be equal to the forward rate consta... | 378 |
reaction kinetics | How does a reaction exhibit kinetics with a non-integer reaction order? | https://chemistry.stackexchange.com/questions/42145/how-does-a-reaction-exhibit-kinetics-with-a-non-integer-reaction-order | <p>What does it mean when the order of reaction isn't an integer, e.g., a reaction order of 2.43. Not with something acting as a catalyst but rather as a inhibitor. Why does the inhibitor produce an unusual reaction order? Specifically fluoride ions slowing down the reaction between calcium carbonate and acid by formin... | 379 | |
reaction kinetics | What is the relation between chemical thermodynamics and chemical kinetics? | https://chemistry.stackexchange.com/questions/44155/what-is-the-relation-between-chemical-thermodynamics-and-chemical-kinetics | <p>Can one be understood on the basis of the other or are they not interrelated at all?</p>
<p>The first thing my kinetics textbook demonstrated was how thermodynamics ignores time taken for a process whereas kinetics considers the time and rate of the process and hence kinetics is a more effective way to view change.... | <p>No. Both I think are equally theoritical or experimental. You must study both seperately. Thermodynamics doesn't speak about rates. While kinetics doesn't tell you stability.
If a reaction produces more than one product, thermodynamics will tell you which is more stable, while that doesn't necessarily mean it is th... | 380 |
reaction kinetics | Differences in AChE inhibition kinetics between VX and VR | https://chemistry.stackexchange.com/questions/147164/differences-in-ache-inhibition-kinetics-between-vx-and-vr | <p>According to the referenced paper, VR has an AChE inhibition reaction rate constant almost 4 times that of VX. Interestingly, its reaction rate constant for aging of the enzyme is less than that of VX, despite the fact that, as acknowledged by the authors of the paper, aging tends to occur faster when the leaving gr... | 381 | |
reaction kinetics | Organic-catalysis microwaves | https://chemistry.stackexchange.com/questions/142850/organic-catalysis-microwaves | <p>When we perform a organic reaction without any addtional catalyst except that the reaction is carried out under microwave condition we can accelerate this reaction in comparison with one under heating only. So, microwaves can be considered a form of catalysis according to the concept of reaction kinetics?</p>
| <p>Here is an example of an entire online GoogleBook dedicated to the topic <a href="https://www.google.com/books/edition/Microwave_Assisted_Organic_Synthesis/CrfzIiN5qlgC?hl=en&gbpv=1&dq=organic+microwave+assisted+synthesis&pg=PR5&printsec=frontcover" rel="nofollow noreferrer">Microwave Assisted Organi... | 382 |
reaction kinetics | Rate of change and kinetics order of reaction question | https://chemistry.stackexchange.com/questions/144756/rate-of-change-and-kinetics-order-of-reaction-question | <p>The rate of reaction is given by the following equation, where [Ker-S-S-Ker] is just the molecule being broken down and [RSH] is an abbreviation for thioglycolic acid</p>
<p>The thioglycolate is in large excess and so essentially remains unchanged.</p>
<p><a href="https://i.sstatic.net/eQb9Q.png" rel="nofollow noref... | <p>Indeed, the only thing you'll need is solving the first order differential equation (but before that, let me define <span class="math-container">$R_0 := \ce{[RSH]_0}$</span> and <span class="math-container">$C :=\ce{[Ker-S-S-Ker]}$</span>.</p>
<p>Now, let's solve it assuming (that's what is given) that <span class="... | 383 |
reaction kinetics | Factors that influence the kinetics of an irreversible exothermic reaction | https://chemistry.stackexchange.com/questions/91147/factors-that-influence-the-kinetics-of-an-irreversible-exothermic-reaction | <p>I'm trying to understand what are the main factors that influence the reaction rate of an irreversible exothermic reaction. </p>
<p>I think these could be the main factors: </p>
<ol>
<li>chemical nature of the reagents and their concentration;</li>
<li>nature of the solution (homogeneous or heterogeneous)</li>
<li... | <p>I assume by kinetics you mean the rate of the reaction (i.e. how fast it happens), in which case the factors you mention are fine. </p>
<p>Regarding the temperature: the rate constant and therefore the reaction rate at a given concentration always increases with temperature as you can see in the Arrhenius equation.... | 384 |
reaction kinetics | How do thermodynamics and kinetics control this reaction? | https://chemistry.stackexchange.com/questions/70344/how-do-thermodynamics-and-kinetics-control-this-reaction | <p>The answer is A, but how is that? I know B is an intermediate, so that after short time it will be bigger than C, but what does "thermodynamic control" and "kinetic control" mean?</p>
<p><a href="https://i.sstatic.net/7yoMM.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/7yoMM.png" alt="https://i.sst... | <p>Initially no B and C exist. At short times as $k_1 > k_2$ production of B is favoured over C. (The initial amounts of B and C are so small that back reactions can be ignored wrt. forwards ones.) At long times equilibrium constants matter and as the equilibrium constant $K_2$ is greatest this is favoured to produ... | 385 |
reaction kinetics | Finding the reaction order from a given plot of chemical kinetics | https://chemistry.stackexchange.com/questions/162616/finding-the-reaction-order-from-a-given-plot-of-chemical-kinetics | <p>What will be the order of the reaction for a chemical change having <span class="math-container">$\log t_{1/2}$</span> VS <span class="math-container">$\log a$</span> Where <span class="math-container">$a=$</span> is the initial concentration of reactant and <span class="math-container">$t_{1/2} =$</span> Half Life?... | <p>The equation that you have derived is correct. For a zeroth-order reaction, <span class="math-container">$$\log t_{1/2}=\log a-\log2K$$</span>
By superficially observing, this seems to be giving a straight line with the equation <span class="math-container">$y=mx-c$</span> but actually there are several(not all) rea... | 386 |
reaction kinetics | Arrhenius equation in Kinetics and Thermodynamics | https://chemistry.stackexchange.com/questions/74634/arrhenius-equation-in-kinetics-and-thermodynamics | <p>It is always stressed that one should never mix Kinetics with Thermodynamic. How is it then possible to calculate the free energy of activation with the Arrhenius equation? As I understood, the Arrhenius equation and thus the activation energy of a reaction "belongs" to kinetics, whereas the free energy represents a... | 387 | |
reaction kinetics | Effect of stirring and shaking on chemical kinetics | https://chemistry.stackexchange.com/questions/150043/effect-of-stirring-and-shaking-on-chemical-kinetics | <p>Why don't we take the effects of stirring and shaking on the rates of chemical reactions? While studying chemical kinetics, I've seen that the rates depend on the concentrations of various species, temperature, pressure, etc. But I've never seen an equation taking into account the mechanical stirring, shaking and ge... | 388 | |
reaction kinetics | Chemical kinetics with the reaction of tert-butyl bromide with azide ion | https://chemistry.stackexchange.com/questions/73243/chemical-kinetics-with-the-reaction-of-tert-butyl-bromide-with-azide-ion | <blockquote>
<p>The reaction of tert-butyl bromide with azide ion in aqueous solution
is proposed to proceed by the following mechanism:</p>
<p>$\ce{(CH3)3CBr(aq) <=>(CH3)3C+(aq) + Br–(aq)}$</p>
<p>$\ce{(CH3)3C+(aq) + N3–(aq) \to (CH3)3CN3(aq)}$</p>
<p>Assuming that $\ce{(CH3)3C+ (aq)}$ achieve... | <p>You really don't have to write all that differential equations. </p>
<p>Note: I'll write all my steps on a paper, since MathJax formatting is a little time-taking at the moment.</p>
<p>Consider the rate laws for the two reactions:
<img src="https://i.sstatic.net/6Dzil.jpg" alt="enter image description here"></p>
... | 389 |
reaction kinetics | Optical techniques for kinetics studies | https://chemistry.stackexchange.com/questions/80848/optical-techniques-for-kinetics-studies | <p>What optical methods can be used to measure the concentration of reacting gases in a reactor during an exothermic and fast reaction? I need to monitor and measure the <em>local concentration of my gases</em> (in the methane production reaction) along a reactor bed in order to be able to clarify the <em>kinetics</em>... | <p>There are a number of techniques but what you would use depends on how you plan to start the reaction. What use to be called Flash-Photolysis and now called Pump-Probe Spectroscopy is the most general and can be used from the femtosecond to multi-second time range. This is a general method as it measured the absorpt... | 390 |
reaction kinetics | Would sodium metal react differently with aqueous solutions than with pure water? | https://chemistry.stackexchange.com/questions/57351/would-sodium-metal-react-differently-with-aqueous-solutions-than-with-pure-water | <p>I know sodium metal reacts violently with water, but what about aqueous solutions (like sodium bicarbonate). Also, what would the reaction kinetics be? </p>
<p>I have watched YouTube videos were a small piece of elementary sodium reacts completely with water in a matter of seconds. Would that also be the case of el... | <p>It helps to know what the reaction actually is. When sodium metal reacts with water, it is oxidised and the hydrogen in water is reduced according to the following equation:</p>
<p>$$\ce{2Na (s) + 2 H2O (l) -> 2 Na+ (aq) + 2 OH- (aq) + H2 ^ (g)}\tag{1}$$</p>
<p>Note that no other components play a role; the onl... | 391 |
reaction kinetics | Auto-catalysis Mechanism | https://chemistry.stackexchange.com/questions/86979/auto-catalysis-mechanism | <p>I just read about the theory of auto-catalysis, and here's one thing which is sort of unclear to me: </p>
<blockquote>
<p>In this type of catalysis, one of the reaction product catalyses the reaction. For example, in the oxidation of oxalic acid by potassium permanganate, Mn(II) cation is formed which is known to... | <p>(1) There are several web sites giving details of this reaction and so this need not be copied out here.</p>
<p>(2,3) Rather than describe a complex reaction scheme it is easier to understand a generic autocatalytic reaction. The general autocatalytic reaction of species A with catalyst B has the form $\ce{A + B $\... | 392 |
reaction kinetics | Conceptual tussle with kinetics of equilibrium and non-equilibrium processes | https://chemistry.stackexchange.com/questions/81039/conceptual-tussle-with-kinetics-of-equilibrium-and-non-equilibrium-processes | <p><strong>Prologue</strong>:</p>
<p>Recently started with <em>Chemical Kinetics</em> at class. Came across a couple of points in Levine's <em>Physical Chemistry</em> (the book was <a href="https://chemistry.stackexchange.com/questions/37303/resources-for-learning-chemistry">recommended on Chem.SE</a>; so I thought I'd... | <p>OK, I think I am correct about this. If not then I suppose somebody will come along and correct me anyway.</p>
<p>The author here is referring to the <strong>net</strong> rate being infinitesimal. To understand where the infinitesimal comes from, we need to figure out what is being meant by an "equilibrium process"... | 393 |
reaction kinetics | Loaded and unloaded solutions | https://chemistry.stackexchange.com/questions/61780/loaded-and-unloaded-solutions | <p>What is the difference between a loaded solution and an unloaded solution? I was reading this article and I didn't understand these parts:</p>
<blockquote>
<ul>
<li>The reaction kinetics of $\ce{CO2}$ with <strong>loaded</strong> aqueous MEA solution...</li>
<li>$\ce{CO2}$ <strong>loading</strong> from $\math... | <p>Unloaded solutions are solutions without absorbed $\ce{CO2}$ and loaded solutions contain absorbed $\ce{CO2}$. Please see the <a href="https://spiral.imperial.ac.uk/bitstream/10044/1/26161/7/acs%252Ejced%252E5b00282.pdf" rel="nofollow noreferrer">this link</a>.</p>
| 394 |
reaction kinetics | How can a reaction exhibit first order kinetics when there is more than one reactant (the other being water) | https://chemistry.stackexchange.com/questions/90475/how-can-a-reaction-exhibit-first-order-kinetics-when-there-is-more-than-one-reac | <p>This is for the hydrolysis of p-nitrophenyl phosphate by alkaline phosphatase, whereby the enzyme is in a solution of distilled water. We also add glycine buffer to the solution. It exhibits first-order kinetics, even though there is a second reactant (being water) - how is this possible?</p>
| <p>It is because water is the solvent in the reaction and therefore its concentration remains practically constant throughout the course of the reaction. Hence, it is absorbed in the rate constant: </p>
<p>rate=k[p-nitrophenyl phosphate]$^1$[H$_2$O]$^x$=k'[p-nitrophenyl phosphate]$^1$</p>
<p>Hence, we say the reactio... | 395 |
reaction kinetics | Half-life equation for 2nd order kinetics | https://chemistry.stackexchange.com/questions/87363/half-life-equation-for-2nd-order-kinetics | <p>My friends and I were doing some problems from this year's IChO Preparatory Problems (<a href="https://icho2017.sc.mahidol.ac.th/pdf/49th_IChO_PreparatoryProblem.pdf" rel="nofollow noreferrer">PDF from the 49th International Chemistry Olympiad (2017)</a>) when we stumbled upon a question which we had some confusion ... | <p>Roughly speaking, <strong>half-life is not a thing at all for the second order</strong> (or <em>any</em> order other than first, for that matter).</p>
<p>What would they do after finding the number of half-lives? Raise 2 to that power? Too bad, because that only works for the exponential decay, which is the solutio... | 396 |
reaction kinetics | Query in Chemical Kinetics | https://chemistry.stackexchange.com/questions/82089/query-in-chemical-kinetics | <p>I have been recently studying chemical kinetics. I've understood what the rate law and the rate constant mean, and also that, kinetics depends completely on experimental observations, due to which we have zero order reactions as well as fractional order reactions.</p>
<p>Take for example, this: $$\text{Rate of a ce... | <p>Order of a reaction can be found by the following methods:</p>
<p><strong>1. Plotting a graph of concentration of reactant versus time</strong></p>
<p>For example, let us take decomposition of <span class="math-container">$\ce{N2O}$</span> to <span class="math-container">$\ce{N2}$</span> and <span class="math-contai... | 397 |
reaction kinetics | Order in Enzyme Kinetics | https://chemistry.stackexchange.com/questions/165992/order-in-enzyme-kinetics | <p>In an interview for post-grad level, I was asked to explain the "order" of any generic enzymatic reaction involving <a href="https://chem.libretexts.org/Bookshelves/Biological_Chemistry/Book%3A_Biochemistry_Online_(Jakubowski)/08%3A_Transport_and_Kinetics/8.4%3A_Enzyme_Inhibition/Competitive_Inhibition" re... | 398 | |
reaction kinetics | What is the non-ideal equivalent of mass action kinetics? | https://chemistry.stackexchange.com/questions/19234/what-is-the-non-ideal-equivalent-of-mass-action-kinetics | <p>Starting from the equations of <a href="http://en.wikipedia.org/wiki/Law_of_mass_action" rel="nofollow">mass action kinetics</a>, one may show that (for suitably chosen numbers $A_i$), the function $\sum_i x_i(A_i + \log x_i)$ is a <a href="http://en.wikipedia.org/wiki/Lyapunov_function" rel="nofollow">Lyapunov func... | <p>According to <a href="http://iglesia.cchem.berkeley.edu/Publications/JournalofMolecularCatalysisA_163_189_2000.pdf" rel="nofollow">Catalytic reaction rates in thermodynamically non-ideal systems</a> Journal of Molecular Catalysis A: Chemical 163 (2000) 189–204 (citing to kinetics textbooks) non-ideal kinetics needs ... | 399 |
chemical bonding | Chemistry chemical bonding | https://chemistry.stackexchange.com/questions/70494/chemistry-chemical-bonding | <p>when a chemical bond is formed, does chemical reaction occur? if i have done a coating on metal substrate then how does it adhere to the substrate? If there is a chemical bond then which reaction does takes place?</p>
| <p>If a chemical bond between atoms is split, or newly generated, than there is occurrence of a chemical reaction. Not all bonds, however, are equal -- covalent bonds differ from hydrogen bonds, for example.</p>
<p>Your question <em>may</em> be interpreted as if you were unsure to discern between <a href="https://en.... | 400 |
chemical bonding | What is this wave function in Chemical bonding? | https://chemistry.stackexchange.com/questions/9612/what-is-this-wave-function-in-chemical-bonding | <p>Was studying chemical bonding(Valence bond theory) but there came this topic called <em>wave equation</em> but have not studied quantum mechanics,so finding hard to understand these terms.Please help!!!</p>
| <p>$\Psi$ is the wavefunction describing an electron's motion. $\Psi^2$ is the probability density function for the electron. $\Psi^2$ is usually interpreted as the probability of finding the electron at a given set of coordinates.</p>
<p>In the case that $\Psi$ is a complex function (in that it contains imaginary nu... | 401 |
chemical bonding | What does chemical bonding look like at the quantum level? | https://chemistry.stackexchange.com/questions/46959/what-does-chemical-bonding-look-like-at-the-quantum-level | <p>How does chemical bonding look like on the quantum scale per se since the electron is a wave, and a particle?</p>
| <p>I believe that generally in chemistry the wave characteristics of the electron are far more prevalent/relevant that the particle characteristics. So it's usually easiest just to think of it as a wave (or I think "region of space" is easier).</p>
<p>A chemical bond looks like the electron wave or area spread out bet... | 402 |
chemical bonding | chemical bonding | https://chemistry.stackexchange.com/questions/186037/chemical-bonding | <p>How exactly does bonding work?
For example, in CH4 orbital overlap structure, the internet shows 4 lobes with one hydrogen attached to each...</p>
<p><a href="https://i.sstatic.net/f9yPx06t.gif" rel="nofollow noreferrer"><img src="https://i.sstatic.net/f9yPx06t.gif" alt="enter image description here" /></a></p>
<p>d... | <blockquote>
<p>[OP] if we talk about the p orbitals in carbon, 3 s-p bonds are formed, hydrogen(s) to carbon(p), p orbital usually consists of 2 lobes, one lobe forms a bond with hydrogen, what does the other one do?</p>
</blockquote>
<p>During the early days of quantum chemistry, researchers were wondering the same t... | 403 |
chemical bonding | Chemical bond-covalent-valence electrons OH- | https://chemistry.stackexchange.com/questions/7264/chemical-bond-covalent-valence-electrons-oh | <p>I would like to ask how many valence electrons took part in creating chemical bond in $\ce{OH-}$? Is the minus related to $\ce{O}$ or to $\ce{H}$? Are there any spare valence electrons which didnt take part in creating chemical bond in $\ce{OH-}$?</p>
| <p><img src="https://i.sstatic.net/BtYqt.jpg" alt="enter image description here"></p>
<p>In the photo the orange electrons are non bond electrons.<br>
And the black electrons are bond electrons.</p>
<p>There are 2 electrons took part in creating chemical bond in $\ce{OH}$.
The first one is from oxygen.<br>
The second... | 404 |
chemical bonding | Chemical bonding | https://chemistry.stackexchange.com/questions/87917/chemical-bonding | <p>How do we compare the strength of permanent dipole permanent dipole (PDPD) interaction? Is it by bond polarity?
Since H-X (where X is halogen) is polar, and for bond polarity (PDPD bond strength): HCl > HBr > HI, why is it that for boiling point: HCl < HBr < HI which is inversely proportional to bond strength... | 405 | |
chemical bonding | Are intermolecular forces a type of chemical bond? | https://chemistry.stackexchange.com/questions/91369/are-intermolecular-forces-a-type-of-chemical-bond | <p>My chemistry teacher told me that chemical bonds are of two types: intramolecular and intermolecular. He said that intermolecular forces come under the category of intermolecular chemical bond. </p>
<p>I have never read such statement anywhere. Nor can I find anything on the Internet that would support this stateme... | <p>The IUPAC <a href="https://goldbook.iupac.org/html/C/CT07009.html" rel="nofollow noreferrer">definition</a> of "chemical bond" is: </p>
<blockquote>
<p>When forces acting between two atoms or groups of atoms lead to the formation of a stable independent molecular entity, a chemical bond is considered to exist bet... | 406 |
chemical bonding | Chemical bond of adsorbed atoms | https://chemistry.stackexchange.com/questions/16475/chemical-bond-of-adsorbed-atoms | <p>When oxygen is adsorbed on iron metallic surface, does it create $\ce{Fe-O}$ bonds like the one in iron oxide? Can it be considered as a monolayer of iron oxide on the surface?</p>
<p>If not, how is the atomic bond of adsorbed oxygen and iron? How much is it strong? and what is its difference with normal chemical b... | 407 | |
chemical bonding | Chemical bond at Aluminum / Aluminum oxide interface | https://chemistry.stackexchange.com/questions/38505/chemical-bond-at-aluminum-aluminum-oxide-interface | <p>I am trying to find out what chemical bond holds aluminum oxide to the aluminum on which it forms. The only information I was able to find on the internet was in a Google book which suggested that the bond was ionic in nature.</p>
| 408 | |
chemical bonding | VSEPR theory, chemical bond and quantum mechanics | https://chemistry.stackexchange.com/questions/89244/vsepr-theory-chemical-bond-and-quantum-mechanics | <p>VSEPR theory correctly predicts the shapes of many symmetry-broken molecules such as $\ce{H2O}$ and $\ce{NH3}$. Take $\ce{NH3}$ for example. In VSEPR theory, the nitrogen atom is (approximately) at the center of a tetrahedron, the three $\ce{N-H}$ bonds point to three of the four vertices of the tetrahedron, and the... | <p><strong>VSEPR is a simple and generalised approach based</strong> (mainly) <strong>on empirical observation.</strong> It is a great theory in predicting, in a first order approximation, the geometrical shape of molecules. That is a lot harder with other methods. It is of course based on a physical foundation, not on... | 409 |
chemical bonding | How do the relativistic effects influence chemical bonding of hassium or other closely related super heavy elements? | https://chemistry.stackexchange.com/questions/184390/how-do-the-relativistic-effects-influence-chemical-bonding-of-hassium-or-other-c | <p>While superheavy elements are notoriously unstable, there's plenty of theoretical research and even some experimental techniques are valid for nuclides decaying in a matter of seconds. They can verify presence of relativistic effects, which may cause behavior defying expectations</p>
<p>How do the relativistic effec... | 410 | |
chemical bonding | Chemical bonding - lattice energy | https://chemistry.stackexchange.com/questions/14132/chemical-bonding-lattice-energy | <p>Question: Why is ionic lattice energy inversely proportional to the radius of the atom?</p>
<p>Most heterogeneous covalent molecules are polar to some extent. The degree of polarity, or the dipole moment, depends on the difference in electronegativity difference between the two atoms. The larger the dipole moment, ... | <p>Considering your doubt, from <strong><em>Born-Lande</em></strong> equation:</p>
<blockquote>
<p>$$E = -\frac{N_\text{A}Mz^+z^- e^2 }{4 \pi \varepsilon_0 r_0}\left(1-\frac{1}{n}\right)$$</p>
</blockquote>
<hr>
<blockquote>
<p>$N_\text{A}$ = <em><strong>Avogadro constant</strong></em>;<br>
$M$ = <em><stro... | 411 |
chemical bonding | Help with chemical bond associated with 1500cm-1 and 1600cm-1 | https://chemistry.stackexchange.com/questions/167866/help-with-chemical-bond-associated-with-1500cm-1-and-1600cm-1 | <p>I have IR spectra of polystyrene with characteristic peaks at 1450cm-1. 1500cm-1 and 1600cm-1. What chemical bond is associated with 1600cm-1 and 1500cm-1?</p>
| <p>As shown <a href="https://www.spectroscopyonline.com/view/the-infrared-spectra-of-polymers-iii-hydrocarbon-polymers" rel="nofollow noreferrer">here</a> (Figure 2), the lines at 1600 and 1492 (~1500) cm<span class="math-container">$^{-1}$</span> correspond to aromatic ring modes.</p>
<p>From my doctoral dissertation ... | 412 |
chemical bonding | Chemical bonding and dipole moment | https://chemistry.stackexchange.com/questions/62262/chemical-bonding-and-dipole-moment | <p>We know that ammonia undergoes amine inversion. Why doesn't the dipole moment decrease in ammonia, since the direction of the dipole changes to the opposite direction every time there's inversion?</p>
<p>Shouldn't the effective dipole moment become zero?</p>
| <p>Ivan Neretin is correct in stating that no particle in a (nondegenerate) state can have a permanent electric dipole moment in the laboratory frame. In fact, a permanent dipole moment would require a violation of time (T) and parity (P) symmetry. This is because any such dipole should be directed along the angular mo... | 413 |
chemical bonding | Chemical bonding with f orbitals | https://chemistry.stackexchange.com/questions/78542/chemical-bonding-with-f-orbitals | <p>For the elements such as rhenium, osmium, iridium how probable is for electrons in the inner 4f orbitals to gain energy and take part in a molecular orbital (such as an $f^2 d^2 s p^3$ hybrid orbital) when these elements are in their 6,7,8,9 oxidation state? </p>
| <p>By transition metals, 4f becomes full and becomes quite deeply buried in the electron cloud. So the main orbitals that participate are 5d and 6s orbitals - especially in ion formation. However in actinides, 5f orbitals are diffuse and so can participate and so chemicals like diuranium have 5f participation. Even at ... | 414 |
chemical bonding | Chemical Anti-bonding and Pauli repulsion | https://chemistry.stackexchange.com/questions/123448/chemical-anti-bonding-and-pauli-repulsion | <p>We can explain chemical anti-bonding just using the Pauli repulsion correct?Let's take He2.</p>
<p>2 atoms of He share 4 1s electrons and since the magnetic spin for electrons has 2 values there would be 2 electrons with the same wave function which would violate the Pauli exclusion principle.This makes He2 unstabl... | <p>The reason we speak of orbitals as being exclusively inhabited by 2 (max) electrons (with opposing electron spin quantum number) is because electrons are fermions and therefore observe the exclusion principle. The exclusion principle constrains the allowed electron configurations, disallowing occupation of lower E o... | 415 |
chemical bonding | Chemical bonding and hybridization of organic compounds | https://chemistry.stackexchange.com/questions/24989/chemical-bonding-and-hybridization-of-organic-compounds | <p>What happens to the lobe of the p-orbital during sp² hybridization?</p>
<p>During the formation of <span class="math-container">$\ce{C2H4}$</span> molecule:</p>
<p>We know that both the carbon atoms will have a total of 3 p-orbitals and they will be involved in hybridization.</p>
<p>Let us number the carbon atoms... | <p>You talk about hybridisation but you haven't actually looked at any hybrid orbitals in your description. Since the geometry around the carbons is trigonal planar, each carbon hybridises its $\ce{2s}$, $\ce{2p}_x$ and $\ce{2p}_y$ orbitals to form three $\ce{sp^2}$ orbitals which lie in the $xy$ plane at $120^\circ$ a... | 416 |
chemical bonding | Chemical bonding based on hybridisation model | https://chemistry.stackexchange.com/questions/109261/chemical-bonding-based-on-hybridisation-model | <p>A snippet from a textbook:</p>
<blockquote>
<p>Therefore, the hybridization model predicts that an <span class="math-container">$\mathrm{sp}$</span>-hybridized carbon atom is more electronegative than an <span class="math-container">$\mathrm{sp}^3$</span>-hybridized carbon atom. Evidence for this effect is that t... | <p>The usual explanation for <span class="math-container">$sp$</span> orbitals being more electronegative than <span class="math-container">$sp^3$</span> is the fact that more <span class="math-container">$s$</span> character means a shorter average distance from the nucleus, thus experiencing a greater effective nucle... | 417 |
chemical bonding | How energy is released when chemical bond is formed? | https://chemistry.stackexchange.com/questions/126598/how-energy-is-released-when-chemical-bond-is-formed | <p>In books it is commonly written that whenever a chemical bond is formed the energy of the molecules/atoms gets lowered and hence energy is released. This is generally explained by diagrams like this </p>
<p><a href="https://i.sstatic.net/uXJub.jpg" rel="noreferrer"><img src="https://i.sstatic.net/uXJub.jpg" alt="en... | <p>Let us assume the simplest case to form a bond from two atoms (assumed to be in their ground state) that approach each other from an infinite distance. For convenience, we put the potential energy of the system at zero here. If the atoms come closer, they start to interact via long-range forces (such as van der Waal... | 418 |
chemical bonding | Why is an ionic bond a chemical and not a physical bond? | https://chemistry.stackexchange.com/questions/32533/why-is-an-ionic-bond-a-chemical-and-not-a-physical-bond | <p>Ionic bonds seem to be intermolecular but are classified as chemical bonds.</p>
<blockquote>
<p>"Ionic bonding is a type of chemical bond that involves the electrostatic attraction between oppositely charged ions." - <em>Wikipedia, definition of an ionic bond</em></p>
<p>"The physical force of attrac... | <p><strong>Short version:</strong></p>
<p>We don't call bonds "physical", there are chemical bonds and other types of interactions between particles. The chemical bonds are classified this way because they make up molecules, salts, polymers and such, which are the materials chemists are interested in studying, and not... | 419 |
chemical bonding | How is energy released when a chemical bond is formed? | https://chemistry.stackexchange.com/questions/111936/how-is-energy-released-when-a-chemical-bond-is-formed | <p>Chemical reactions are classed as endothermic or exothermic.</p>
<p>Defn: exothermic</p>
<blockquote>
<p>(of a reaction or process) accompanied by the release of heat.</p>
</blockquote>
<p>The heat is released when the chemical bonds in the product are formed.</p>
<p>Defn: heat</p>
<blockquote>
<p>heat is e... | <p>It is easier first to think of what happens when a bond is broken in an exothermic reaction. The energy is initially released into vibrations, rotations and translational motion of the two fragments. This energy is then lost as these fragments collide with other gas molecules or with solvent molecules and so eventu... | 420 |
chemical bonding | Squiggly line in chemical bond notation | https://chemistry.stackexchange.com/questions/145043/squiggly-line-in-chemical-bond-notation | <p>In general is there a convention as to how one interprets squiggly lines in chemical structure notation?</p>
<p>e.g. see the below sketch. I suppose it has something to do with cis / trans isomerism. But e.g. where do you draw the squiggly i.e. which side of the double bond? Is it used in other contexts as well? And... | 421 | |
chemical bonding | Is the 3D spacing arrangement of atoms in chemical bond always unique? | https://chemistry.stackexchange.com/questions/163336/is-the-3d-spacing-arrangement-of-atoms-in-chemical-bond-always-unique | <p>I would like to ask if the 3D spacing arrangement of atoms in chemical bond configurations are always unique, please?</p>
<p>For example, glycine consists of the set of atoms HHNCHHCOOH. Does there exist a different stable 3D arrangement of this collection of atoms, other than:</p>
<p><a href="https://i.sstatic.net/... | <p>From a given number of atoms, you can usually construct multiple molecules (isomers), so we shall just concentrate on the case where the bond connectivity is the same.</p>
<p>The terms you are looking for are <em>conformation</em> and <em>configuration</em>. The latter is most usually related to double bonds and E/Z... | 422 |
chemical bonding | What does CkC mean in chemical bonding? | https://chemistry.stackexchange.com/questions/93953/what-does-ckc-mean-in-chemical-bonding | <p>I'm working on a chemistry question where I'm supposed to use average bond energies to estimate enthalpy changes for a reaction. It gives me these bond energies to work with:</p>
<p>$$\begin{align}
\ce{C-H}&=&413\\
\ce{C-C}&=&348\\
\ce{C-Br}&=&276\\
\ce{H-Br}&=&366\\
\ce{CkC}&=&a... | <p>$\ce{C=C}$ <strong>average bond energy</strong> is somewhere around $\pu{614 kJ/mol}$ so "k" probably indicates a double bond</p>
| 423 |
chemical bonding | Chemical bonding and crystal structure of silicon | https://chemistry.stackexchange.com/questions/133493/chemical-bonding-and-crystal-structure-of-silicon | <p>I can understand that in Silicon Crystal a central Silicon atom shares its 4 valance electrons with 4 surrounding silicon atoms. And the chain continues. But then What happens to the outermost such Silicon atoms (in the drawing). They each will have incomplete so called octate.</p>
| <p>In a Silicon crystal, outermost Silicon atoms are probably oxidized yielding a monoatomic layer of Oxygen atoms, chemically bound by covalences like in <span class="math-container">$\ce{SiO_2}$</span>, by analogy with Aluminium. Silicon and Aluminium are neighbors in the periodic table : they often have similar prop... | 424 |
chemical bonding | Which chemical reactions don't involve bond breaking? | https://chemistry.stackexchange.com/questions/99967/which-chemical-reactions-dont-involve-bond-breaking | <p>I recently came across a question in which an option is 'Breaking a chemical bond is the first step in any chemical reaction', which lead me to think of reactions which do not involve bond breaking. The only reaction I can think of is dimer formation, but a Google search reveals no more. Surely this cannot be the on... | <p>The reaction of a Lewis acid with a Lewis base results only in bond formation. Your question gets at the essence of chemistry, though. A chemical reaction is the rearrangement of electrons between atoms. So generally, most reactions will involve breaking bonds. Even for monomers (e.g. alkenes) to polymerize, $\pi$-b... | 425 |
chemical bonding | Spatial form of an atom and type of chemical bond | https://chemistry.stackexchange.com/questions/68768/spatial-form-of-an-atom-and-type-of-chemical-bond | <p>As we know, the first excited states of Hydrogen atoms is $2p$.
The wave functions in cartesian basis we can represent as
$$
p_x = \frac{1}{\sqrt{2}} \left( Y_{1, +1} + Y_{1, -1}\right) =\sqrt{\frac{3}{16\pi}} \frac{x}{r} \\
p_y = \frac{i}{\sqrt{2}} \left( Y_{1, +1} - Y_{1, -1}\right) = ... | 426 | |
chemical bonding | why chemical bond between Na and Cl happens | https://chemistry.stackexchange.com/questions/173378/why-chemical-bond-between-na-and-cl-happens | <p>We know that if Cl and Na get too close, they produce ionic bonding.</p>
<p>Cl has 17 proton and 17 electrons and is considered stable.</p>
<p>Na has 11 protons and 11 electrons and is considered stable.</p>
<p>I understand that in Na, we have 1 valence electron and in Cl, we have 7 valence electrons. Now, if they g... | <p>Here is an easier explanation not relying on "stability" or quantum mechanics.</p>
<p>You start out with some sodium ions and some chloride ions in aqueous solution. Each sodium ion is surrounded by water, and each chloride ion is surrounded by water. Then, you let the water evaporate, the sodium and chlor... | 427 |
chemical bonding | Quantum chemistry and covalent bonding | https://chemistry.stackexchange.com/questions/175972/quantum-chemistry-and-covalent-bonding | <p>How can the formation of a covalent bond be described from a quantum perspective, and what implications does it have for traditional chemical bonding theory?</p>
<p>Specifically, in the context of many-electron systems where electron correlation becomes significant, how do modern quantum chemical methodologies, such... | <p><strong>Quantum Chemistry and Covalent Bonding:</strong></p>
<p>Quantum chemistry, a nexus between quantum mechanics and molecular science, furnishes an in-depth framework for comprehending and predicting the nuances of chemical bonding. By incorporating quantum principles, this domain offers a granular look into el... | 428 |
chemical bonding | Would a hypothetical Og2 +235 form a chemical bond? | https://chemistry.stackexchange.com/questions/169595/would-a-hypothetical-og2-235-form-a-chemical-bond | <p>In a hypothetical (?) Og<sub>2</sub><sup>+235</sup> we would have a simple sigma bonding orbital occupied by one electron (leading to a bond order of 1/2). But how to take into account the giant repulsion of the two nuclei? Generally how are nucleis taken into account for energy calculations from molecular orbitals ... | <p>I would not bet on it. We apparently can't even get <span class="math-container">$\ce{He2^{3+}}$</span>, let alone higher single-electron diatomic ions. From <a href="https://en.wikipedia.org/wiki/Helium_compounds" rel="nofollow noreferrer">Wikipedia</a>:</p>
<blockquote>
<p><span class="math-container">$\ce{He2^+}$... | 429 |
chemical bonding | Explanation of certain chemical bond diagrams | https://chemistry.stackexchange.com/questions/14460/explanation-of-certain-chemical-bond-diagrams | <p>Here's a "simple" bond diagram of 1,1,1,2-Tetrafluoroethane which I believe is a Lewis structure:</p>
<p><a href="https://upload.wikimedia.org/wikipedia/commons/thumb/a/a4/1,1,1,2-Tetrafluoroethane.svg/100px-1,1,1,2-Tetrafluoroethane.svg.png" rel="nofollow noreferrer"><img src="https://upload.wikimedia.org/wikipedi... | <p>The second structure you posted is a line angle diagram. In this diagram, methyl groups (-CH3) are implied using sticks with nothing at the end.</p>
<p><img src="https://i.sstatic.net/kXRjA.png" alt="enter image description here"></p>
<p>Carbon atoms are also implied; carbons exist at every "corner" of the polygon... | 430 |
chemical bonding | Is a chemical, molecular bond considered more effective for paint adhesion than the often-recommended “mechanical bond” by roughening a substrate? | https://chemistry.stackexchange.com/questions/187939/is-a-chemical-molecular-bond-considered-more-effective-for-paint-adhesion-than | <p>Both in fine art, decorative and in utilitarian painting, sanding or roughening a substrate to provide a so-called “mechanical bond” has often been recommended as a preliminary step before applying paint.</p>
<ol>
<li><p>Interestingly, sanding is said to both roughen a surface, giving it some “tooth” for paint to ad... | 431 | |
chemical bonding | How to define a chemical bond computationally? | https://chemistry.stackexchange.com/questions/165918/how-to-define-a-chemical-bond-computationally | <p>I'm working with an amorphous system. With oxygen, my system has both covalent and ionic bond forming cations. I utilise the <a href="https://en.wikipedia.org/wiki/Wannier_function" rel="nofollow noreferrer">Wannier centre</a> to define a covalent bond, and my theory is that if the Wannier centre is near to the line... | 432 | |
chemical bonding | What does it mean by non-bonding p pi orbital? | https://chemistry.stackexchange.com/questions/157594/what-does-it-mean-by-non-bonding-p-pi-orbital | <p>In a paper by Peng <em>et. al.</em>,<sup>[1]</sup> I read about the valence band maximum of <span class="math-container">$\ce{TiO2}$</span> consists of <strong>non-bonding O p<sub>π</sub></strong> orbitals</p>
<blockquote>
<p>... the valence band maximum (VBM) consists of non-bonding O p<sub>π</sub> states</p>
</blo... | <p>When you have atoms bonded all in one plane, there will be <span class="math-container">$p$</span> orbitals oriented perpendicular to the plane which may not interact significantly with adjacent atoms. Such orbitals would then be called nonbonding.</p>
<p>We may compare water with carbon dioxide. Introductory textbo... | 433 |
chemical bonding | How does hydrogen bonding affect the boiling points of chemical compounds? | https://chemistry.stackexchange.com/questions/76727/how-does-hydrogen-bonding-affect-the-boiling-points-of-chemical-compounds | <p>My main question is why is the boiling point of methanol so much different from that of water? </p>
<p>I understand that both compound are able to develop hydrogen bonding, and obviously water can develop one more hydrogen bond than methanol. </p>
<p>But on the other hand:</p>
<blockquote>
<p>Due to presence of... | <p>A hydrogen bond is a particularly strong dipole:dipole interaction with some covalent character. If we ignore the covalent character for a moment, we can say the higher the partial positive charge on the hydrogen, the stronger the hydrogen bond (keeping the O-H bond distance constant). If you relate "electron defici... | 434 |
chemical bonding | How does a reduction in potential energy in a chemical bond release energy | https://chemistry.stackexchange.com/questions/176232/how-does-a-reduction-in-potential-energy-in-a-chemical-bond-release-energy | <p>This question has to do with the idea of stability and energy. The premise is that systems will tend towards lower energy states, that’s why bonding happens and electrons prefer single orbitals. And that makes sense in all considering the second law of thermodynamics, but it still doesn’t answer what causes the rele... | <p>Consider <span class="math-container">$$\ce{2 H <=> H2^{*} ->[collision][emission] H2 + energy}.$$</span></p>
<p>Imagine a hydrogen atom figuratively rolling down to the potential pit of the bond with another hydrogen atom.</p>
<p>Without passing energy elsewhere, it will bounce and appear free again, keepi... | 435 |
chemical bonding | Using real wave functions for chemical bond explanation | https://chemistry.stackexchange.com/questions/91050/using-real-wave-functions-for-chemical-bond-explanation | <p>My question related with another one <a href="https://physics.stackexchange.com/questions/387723/shape-of-hydrogen-atom-in-excited-state-with-nonzeros-angular-momentum">here</a>.</p>
<p>For explanation valence bond direction chemists are used real wave functions, for example $p_x, p_y, p_z, \ldots$. But this functi... | <p>Chemists use the linear combinations of hydrogen atom wavefunctions which are real because this is simply much more convenient to think about. Notice that for hydrogen, all the orbitals for a given $n$ are degenerate, so taking these linear combinations does not affect the energy, and thus thinking about the shapes ... | 436 |
chemical bonding | When calculating a dihedral angle for a chemical bond, how is the direction defined? What are the most common convention? | https://chemistry.stackexchange.com/questions/40181/when-calculating-a-dihedral-angle-for-a-chemical-bond-how-is-the-direction-defi | <p>I understand the geometry and calculation of a dihedral angle, discussed in <a href="https://math.stackexchange.com/q/47059/221321">this question</a>. It is not clear how the direction is defined for a chemical bond. On the <a href="https://en.wikipedia.org/wiki/Dihedral_angle" rel="nofollow noreferrer">wiki page f... | <p>The <a href="http://goldbook.iupac.org/T06406.html" rel="nofollow">IUPAC Gold Book</a> states that, </p>
<blockquote>
<p>In a <a href="http://goldbook.iupac.org/N04134.html" rel="nofollow">Newman projection</a> the torsion angle is the angle (having an absolute value between 0° and 180°) between bonds to two spec... | 437 |
chemical bonding | Does the diiodide(1−) anion exist? | https://chemistry.stackexchange.com/questions/87971/does-the-diiodide1%e2%88%92-anion-exist | <p>With respect to chemical bonding does the $\ce{I2-}$ ion exist?</p>
| <p>I found a <a href="http://pubs.acs.org/doi/pdf/10.1021/jp0671087" rel="nofollow noreferrer">paper</a><span class="math-container">$\ce{^{[1]}}$</span> regarding the formation of diiodide anion species(<span class="math-container">$\ce{I2^-}$</span>). It is assumed to be an unstable species which forms during the for... | 438 |
chemical bonding | Can d-orbitals participate in bonding? | https://chemistry.stackexchange.com/questions/33869/can-d-orbitals-participate-in-bonding | <p>My textbook says:</p>
<blockquote>
<p>It is appropriate to remark that the trick of rationalizing apparent violations of the octet rule by invoking the participation of d-orbitals in the bonding scheme is a matter of some controversy. Some scientists feel that the d-orbitals lie so high in energy that they should no... | <p>Yes it works, according to result they have with organometallic chemistry. You may not know $e_g$ and $t_{2g}$ orbitals. Have a look at this diagram of orbitals : </p>
<p>Its diagram for an octaedric complex, where M is the metal. Positions of $e_g$ and $t_{2g}$ depends of what L is. </p>
<p><img src="https://i.ss... | 439 |
chemical bonding | Antimatter molecules properties | https://chemistry.stackexchange.com/questions/116704/antimatter-molecules-properties | <p>Do the antimatter molecules have the same chemical properties with matter molecules?Should we define electropositivity for antimatter molecules since the chemical bonding would be between positrons?</p>
| <p>The following is an approximation based on the most accepted theories about cosmology (that I know of).</p>
<p>We currently consider that our observable universe is composed only of normal matter, by opposition with antimatter. Also, matter and antimatter should have the exact same physical and chemical properties.... | 440 |
chemical bonding | If hydrogen bonds are chemical bonds, and these bonds are broken when water changes phases, why doesn't this classify as a "chemical" change? | https://chemistry.stackexchange.com/questions/85906/if-hydrogen-bonds-are-chemical-bonds-and-these-bonds-are-broken-when-water-chan | <p>This is more of a terminology question. How are phase changes considered a physical property, not a chemical property when hydrogen bonds break. A chemical property can only be observed during a chemical change. Aren't hydrogen bonds a type of chemical bond, and those bonds are being broken during a phase change fro... | <p>You must realize that the line between physical and chemical properties is very thin. Most bonds work via the same principle, which has mostly to do with electronegativity. When looked at in reactions it has probably also to do with the according entropy and enthalpy change. Hydrogenbonds are basically bonds based o... | 441 |
chemical bonding | Bonding in the nitrate anion | https://chemistry.stackexchange.com/questions/118527/bonding-in-the-nitrate-anion | <p>Hi so I was studying chemical bonding where i encountered a problem which is stated below.</p>
<p>When we talk about <span class="math-container">${NO_3}^-$</span> we draw its structure as following
<img src="https://i.sstatic.net/Q8cda.jpg" alt="enter link description here">
But the thing which I dont understand i... | <p>The problem lies in the electron count. Each bond contains 2 electrons and the pair is counted twice, once for being around each atom in the bond. And don't forget the extra electron to make the ion.</p>
<p>The + and - are from the point of view of the atom nucleus: e.g., consider the nitrogen to share 2 electrons ... | 442 |
chemical bonding | If chemical bonding is quantum mechanic, is saying they bend and vibrate like springs wrong? | https://chemistry.stackexchange.com/questions/41889/if-chemical-bonding-is-quantum-mechanic-is-saying-they-bend-and-vibrate-like-sp | <p>I don't know much about quantum mechanics, but I do know that it's quite far removed from the easily observable and that anything "quantum" involves things that are discreet. So, how close is the analogy between molecular bending and vibration with that of springs? Is there maybe a better way to think, maybe a bette... | <p>That's a good question, but remember, an analogy is just that: comparing <em>dissimilar</em> things on the basis of structure or function. Though there may not be a <em>physical</em> similarity, the analogy is effective in describing what happens, and can even be used to calculate outcomes, within limits.</p>
<p>In... | 443 |
chemical bonding | Textbook Claim: "... in all cases it is the electrostatic force acting between charged particles that is responsible for all the forms of bonding." | https://chemistry.stackexchange.com/questions/111708/textbook-claim-in-all-cases-it-is-the-electrostatic-force-acting-between-c | <p>I am reading an introductory semiconductor physics textbook. The textbook states the following:</p>
<blockquote>
<p>Several types of atomic bonding have been identified, including ionic, covalent, van der Waals, hydrogen, and metallic. Whatever the name given to the type of bonding, in all cases it is the electro... | <p>You ask how bonding between two neutral atoms can be electrostatic. In the case of covalent and van der waals the electrostatic basis is not so obvious as it is for ionic compounds. A covalent bond forms when two neutral atoms establish a shared molecular orbital which is much larger than the separate atomic orbital... | 444 |
chemical bonding | Energy Levels of Molecular Orbitals formed by combination of Atomic Orbitals | https://chemistry.stackexchange.com/questions/125090/energy-levels-of-molecular-orbitals-formed-by-combination-of-atomic-orbitals | <p>In general when we talk about chemical bonding, we say that it is "nature's way to stabilize the systems" and the energy of the molecule formed by atoms will be lower than that of the individual atoms; hence leading to stabilization. </p>
<p>However, while reading about the Molecular Orbital Theory in my NCERT Chem... | 445 | |
chemical bonding | Does it sometimes take energy to create a chemical bond? | https://chemistry.stackexchange.com/questions/118911/does-it-sometimes-take-energy-to-create-a-chemical-bond | <p><a href="https://simple.wikipedia.org/wiki/Molecule" rel="nofollow noreferrer">Wikipedia</a> says so:</p>
<blockquote>
<p>Bonds can also be broken apart. Since most bonds require energy to form, they also give off energy when they are broken. But before most bonds break, the molecule has to be heated. Then the at... | <p>"Molecules that require less energy to break than they give off when broken are called fuels." is the most imprecise sentence in the paragraph, because fuels don't give off energy when their bonds are broken, but when these broken bonds form new bonds (with oxygen) that are much more stable and release more energy t... | 446 |
chemical bonding | Pi bond need sigma bond to exist | https://chemistry.stackexchange.com/questions/58300/pi-bond-need-sigma-bond-to-exist | <p>My teacher was teaching about chemical bonding and she said that pi bond needs sigma bond to exist, but she didn't know why. It is a doubt which I get in my mind, can someone explain it?</p>
| <p>I think it would be more correct to say that pi bonds tend to exist in conjunction with sigma bonds, rather than that they <em>need</em> sigma bonds to exist - as pointed out in the comments. </p>
<p>This can be explained rather easily by basic molecular orbital (MO) theory, which seems like an appropriate framewor... | 447 |
chemical bonding | Bond angles in sulfate | https://chemistry.stackexchange.com/questions/37875/bond-angles-in-sulfate | <p>My chemical bonding professor says that the $\ce{O-S-O}$ bond angles in $\ce{SO4^2-}$ are ideal (109.5°).</p>
<p>Why? Is this because all bonds are equivalent, and electron distribution is shared among all oxygens?</p>
| <p>Yes. All the bonds are equivalent as in the 4 resonating structures, each with 1.5 S and O bonds. So the resonant hybrid has four 1.5 double bonds (sigma and pi) with -0.5 formal charge on each O. This is why, the ion has a perfect tetrahedral geometry and shape as it is very symmetric and equivalent.
Hope it helps.... | 448 |
chemical bonding | What is the difference between physical and chemical bonds? | https://chemistry.stackexchange.com/questions/230/what-is-the-difference-between-physical-and-chemical-bonds | <p>If you characterize the chemical bonds to two categories physical and chemical bonds, how do you do it? Aren't all bonds <strong><em>chemical and physical</em></strong>?</p>
<p>From the freedictionary.com, chemical bond:</p>
<blockquote>
<p>Any of several forces, especially the ionic bond, covalent bond, and met... | <p>In short: the definition of a chemical bond is not unique and a clearly-drawn line. The simplest and most common definition is <strong>the sharing of electrons between two or more nuclei</strong>. In contrast, other interactions are often said to be <em>intermolecular</em> (which is somewhat more specific than the t... | 449 |
spectroscopy | Statistical methods used for testing the homogeneity of the sample | https://chemistry.stackexchange.com/questions/139661/statistical-methods-used-for-testing-the-homogeneity-of-the-sample | <p>So, if I have multiple FTIR spectra each taken on different location of the sample and averaged from ~20 spectra, how can I check if the sample is homogeneous, i.e., if there are statistically significant differences between the spectra based on location? For visuals, I tried to compute at each wavenumber confidence... | 450 | |
spectroscopy | Can you do SERS without a Raman microscope? | https://chemistry.stackexchange.com/questions/142749/can-you-do-sers-without-a-raman-microscope | <p>Surface-enhanced Raman spectroscopy or surface-enhanced Raman scattering (SERS) is a surface-sensitive technique that enhances Raman scattering by molecules adsorbed on rough metal surfaces or by nanostructures such as plasmonic-magnetic silica nanotubes.</p>
<p>Does this require a Raman microscope? Remember you are... | 451 | |
spectroscopy | How to compute Franck-Condon Factors for spin-orbit states? | https://chemistry.stackexchange.com/questions/145328/how-to-compute-franck-condon-factors-for-spin-orbit-states | <p>I am computing Franck-Condon Factors between the neutral ground state and cationic states to simulate the photoelectron spectra (using Gaussian 16, freq=FCHT). The target cationic state is a pi state and has 3/2 and 1/2 spin-orbit components. I have done optimization and frequency calculation for the pi state in TDD... | 452 | |
spectroscopy | Fourier transform for spectroscopy spectra? | https://chemistry.stackexchange.com/questions/3957/fourier-transform-for-spectroscopy-spectra | <p>I was thinking back to my chemistry major days and remembering the bunch of cool spectra we produced by various means (HNMR, IR, UV/Vis) and I remember all the cool 'self-interference' like couplets, triplets doublets, etc. </p>
<p>My question is basically motivated by the complexity of spectra, and the reductionis... | <p>As Mad Scientist said, many spectroscopy methods are already based on Fourier transform of a time-dependent observable. (This is not true of the basic <a href="http://en.wikipedia.org/wiki/Spectrophotometry" rel="noreferrer">spectrophotometry</a> measurements, where you directly measure the transmittance as a functi... | 453 |
spectroscopy | Explanation of the Selection rule in light of IR spectroscopy | https://chemistry.stackexchange.com/questions/4488/explanation-of-the-selection-rule-in-light-of-ir-spectroscopy | <p>I am in mathematics, but I am writing a paper on molecular vibrations (because you can use representation theory to handle this).</p>
<p>I want to prove the selection-rule, but I also have to give a presentation of my intermediate results. Can someone give a little (maybe trivial) explanation (in one or maximal two... | <p>The operator for interaction with infrared light is the permanent dipole of the molecule, $\mu$. I don't know anything about representation theory, but in group theory, you decompose the molecule by its symmetry elements to find the eigenmodes. The infrared active modes are those modes in which the permanent dipol... | 454 |
spectroscopy | What does the signals in a XPS spectrum mean? | https://chemistry.stackexchange.com/questions/4772/what-does-the-signals-in-a-xps-spectrum-mean | <p>I was trying to figure out the different peaks in a XPS spectrum for Molybdenum, but I could not understand them. About XPS, I know that this technique is based on the binding energy of the electrons of different elements</p>
| <p>you are quite right, XPS does measure the 'binding energy' of electrons. More specifically, XPS bombards a surface with X-rays and when those X-rays have sufficient energy they are able to sufficiently excite electrons to be emitted from the sample. Each peak in an XPS spectrum corresponds to the energy necessary to... | 455 |
spectroscopy | How did Scientists Capture The First Images of Molecules Before and After Reaction? | https://chemistry.stackexchange.com/questions/5170/how-did-scientists-capture-the-first-images-of-molecules-before-and-after-reacti | <blockquote>
<p>Using a state-of-the-art atomic force microscope, the scientists have taken the first atom-by-atom pictures, including images of the chemical bonds between atoms, clearly depicting how a molecule's structure changed during a reaction. Until now, scientists have only been able to infer this type of inf... | <p>There are a ton of papers on how AFM works, but I'll have a go at explaining it anyhow.</p>
<p>Atomic Force Microscopy (AFM) is a venerable technology for imaging nanostructures down to individual molecules by physically contacting atoms on surfaces. The whole process is very similar to a finger reading Braille.</p... | 456 |
spectroscopy | Do chemical compounds have spectral lines, or only elements? | https://chemistry.stackexchange.com/questions/5235/do-chemical-compounds-have-spectral-lines-or-only-elements | <p>I know that elements (ex. Ag) have spectral/emission/absorption lines, but do chemical compounds (ex. NaCl) have spectral lines as well? Ones that when seen you can tell that that compound (NaCl) is made up of certain elements (Na and Cl).</p>
| <p>Yes, but for "spectral lines" the gaseous state would generally be the implication. In solids and liquids photon interactions are generally over "bands" of energy not a very discrete wavelength as in a "spectral line."</p>
| 457 |
spectroscopy | Are there any molecules with the same spectrum? | https://chemistry.stackexchange.com/questions/6994/are-there-any-molecules-with-the-same-spectrum | <p>Are there any two distinct types of atom or molecule that have identical emission or absorption spectra?</p>
| <p>In addition to the R/S chiral molecules mentioned by @user26143. There are also molecules with a distinct atomic composition that have experimentally indistinguishable spectra, even though theoretically there will be minor differences. One example, according to <a href="http://link.aps.org/doi/10.1103/PhysRevLett.10... | 458 |
spectroscopy | Red glow in the dark pigments | https://chemistry.stackexchange.com/questions/7096/red-glow-in-the-dark-pigments | <p>I want to do some spectrometry experiments with glow in the dark paints. The red paints I've read product details for all seem to require a uv light to charge. Are there any red glow in the dark paints that can be charged with visible light?</p>
<p>I was also wondering why most red phosphorescent pigments don't hav... | <p>The wikipedia page on <a href="http://en.m.wikipedia.org/wiki/Phosphorescence" rel="nofollow">Phosphoresence</a> has a red pigment. Calcium Sulfide. I can imagine that the lower energy (higher wavelength, lower energy) is more stable because the triplet is not as high in state energy as lower wavelength emitters. Be... | 459 |
spectroscopy | Why does the excitation and emission spectrum of a fluorescent molecule have overlap? | https://chemistry.stackexchange.com/questions/7235/why-does-the-excitation-and-emission-spectrum-of-a-fluorescent-molecule-have-ove | <p>Question is rather self-explanatory. Came up during a lecture without a concrete answer. </p>
<p>I understand that the differences in emission wavelengths is due to relaxation to the lowest energy level of S1, but <strong>why do fluorescent molecules necessarily overlap in their excitation and emission spectra?</st... | <p><a href="https://i.sstatic.net/mnC9H.png" rel="nofollow noreferrer">Energy-Level Diagram</a>
<br>There is overlap because between the excitation and the emission spectra because there exists a Range of orbitals at different energies. You'll always notice that the energy for excitation is always higher, or the lambda... | 460 |
spectroscopy | Is visible spectroscopy the only non-electronic method of all the spectroscopy method? | https://chemistry.stackexchange.com/questions/10928/is-visible-spectroscopy-the-only-non-electronic-method-of-all-the-spectroscopy-m | <p>Is visible spectroscopy the only non-electronic method of all the spectroscopy method?</p>
<p>I know some of the spectroscopy method is possible being used because of electronics.</p>
| <p>No, Ultraviolet spectroscopy and Infra-red spectroscopy were practiced without any use of electricity. </p>
<p>Infra-red and ultraviolet light were both known by 1801.</p>
<p>Ultraviolet absorption lines had been observed by 1843. </p>
| 461 |
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