instruction stringlengths 15 21.8k |
|---|
Who devised the term elements? |
I'm trying to understand ions.
From what I understand, an ion is when the atom gains or loses electrons. More electrons means it is negatively charged (anion). Less electrons means it is positively charged (cation).
My problem is with the following premise:
> Many atoms gain/lose electrons with the hope of hav... |
I'm working on a project that identifies average characteristics of different elements. I'm stuck on lithium, I can't find a way to ratio lithium I and lithium II that symbolizes how it is in nature. I tried looking around on the internet but I haven't found any mention of ratios to ions only ratios to isotopes. Does a... |
I'm trying to understand ions.
From what I understand, an ion is when the atom gains or loses electrons. More electrons means it is negatively charged (anion). Less electrons means it is positively charged (cation).
My problem is with the following premise:
> Many atoms gain/lose electrons with the hope of hav... |
The correct answer for this question is **A**.
Prior to start explaining the answer for your question, I would like to show you a mistake you have done.
You have said
>"**any gas has a volume of 22.4 litres regardless of what the gas is.**"
This true only if the gas exist in standard temperature and pressure ... |
The correct answer for this question is **A**.
Prior to start explaining the answer for your question, I would like to show you a mistake you have done.
You have said
>"**any gas has a volume of 22.4 litres regardless of what the gas is.**"
This true only if the gas exist in standard temperature and pressure ... |
Why doesn’t diamond have $\Delta H_\mathrm{f}^\circ=0$, when graphite does? Is it something to do with the definition – diamonds can’t really form at STP, even though it is naturally occurring? |
Why is the standard enthalpy of formation of diamond not zero? |
I'm trying to understand ions.
From what I understand, an ion is when the atom gains or loses electrons. More electrons means it is negatively charged (anion). Less electrons means it is positively charged (cation).
My problem is with the following premise:
> Many atoms gain/lose electrons with the hope of hav... |
Okay, let me give you the screen shot of this doubtful question.
![enter image description here][1]
**I got the answer for the Roman number 1,here is the way I did it,**
- Since they have given the pH ,I did found the $\ce{[H^+~(aq)]}$
\begin{align}
\mathrm{pH} &=-\log[\ce{H^+~(aq)}]\\
[\ce{H^+~(aq)}] ... |
I always (possible naively) thought that elements are either natural or synthetic, either one or the other. But, according to the Wikipedia page about [Synthetic Elements][1], it states that:
> All elements with atomic numbers 1 through 98 are naturally occurring at least in trace quantities, but the following elem... |
Is there an abundance threshold of a 'synthetic' element for it to be considered natural? |
For the sake of the question,let's assume that you are provided with two labelled rods of the pure metals **A** and **B** and two unlabelled bottles containing $1.0 moldm^{-3}$ aqueous solution of $A^{m+}$ and the other bottle containing $1.0 moldm^{-3}$ aqueous solution of $B^{n+}$ .
So here ,if I want to ... |
How to identify the two solutions and the which of given electrodes is reducing more? |
For the sake of the question, let’s assume that you are provided with two labelled rods of the pure metals $\ce{A}$ and $\ce{B}$ and two unlabelled bottles containing $1.0\ \mathrm{mol\ dm^{-3}}$ aqueous solution of $\ce{A^{$m$+}}$ and the other bottle containing $1.0\ \mathrm{mol\ dm^{-3}}$ aqueous solution of $\ce{B... |
I'm reading document about Solid phase protein synthesis (SPPS) from Wikipedia
https://en.wikipedia.org/wiki/Peptide_synthesis#Solid-phase_synthesis
And according to the document:
> SPPS is limited by yields, and typically peptides and proteins in the
> range of 70 amino acids are pushing the limits of syntheti... |
Why solid phase peptide synthesis is limited to 70 amino acids? |
Below is a transcript of [this][1] doubtful question:
> A weak monobasic organic acid **HA** issoluble in both solvents, water
> and $\ce{CHCl3}$. 500.0 cm$^{3}$ of a solution of $\ce{HA}$ is 0.057
> mol dm$^{-3}$, is shaken well with 500.0 cm$^{3}$ of water and allowed
> to attain equilibrium at $27^{\circ}\mat... |
The first step toward answering this question is understanding the extent to which the statement "Group 11 metals are unreactive" is or isn't true.
As stated in [How do plants respond to copper deficiency?][1] *Plant Signaling and Behavior* vol. 3, pages 231-232:
>The transition metal copper is essential for al... |
Under "[reducing agent][1]" in Wikipedia it says
> good reducing agents are reagents that deliver H<sub>2</sub>
Wouldn't that make water unsafe to dissolves oxidizing agents?
[1]: https://en.wikipedia.org/wiki/Reducing_agent |
Are aquaeos solutions of oxidizing agents safe? |
> Is there a natural abundance threshold of a 'synthetic' element for it
> to be considered natural?
$\mathrm{> 0}$, in other words, any element that can be detected outside of the laboratory (*e.g.* in the natural environment). This would include the 80 stable elements along with the 18 radioactive elements with ... |
> Is there a natural abundance threshold of a 'synthetic' element for it
> to be considered natural?
$\mathrm{> 0}$, in other words, any element that can be detected outside of the laboratory (*e.g.* in the natural environment). This would include the 80 stable elements along with the 18 radioactive elements with ... |
The first step toward answering this question is understanding the extent to which the statement "Group 11 metals are unreactive" is or isn't true.
As stated in [How do plants respond to copper deficiency?][1] *Plant Signaling and Behavior* vol. 3, pages 231-232:
>The transition metal copper is essential for al... |
$\Delta G = -n {\mathcal F} \Delta {\mathcal E} $
$\mathcal F$ is Faraday's constant, which physicists currently believe has been constant throughout the universe for all time. $n$ is the number of electrons transfered in an electrochemical reaction. For a given reaction, $n$ is also constant in all places and tim... |
In the "[reducing agent][1]" article in Wikipedia it says
> Good reducing agents are reagents that deliver $\ce{H2}$.
Wouldn't that make water unsafe to dissolve oxidizing agents?
[1]: https://en.wikipedia.org/wiki/Reducing_agent |
The book's explanation about a noble gas configuration is somewhat accurate, but fairly incomplete.
The elements on the right and on the left of the periodic table (the alkali (earth) metals, the halogens, the chalcogens (the group that starts with Oxygen) and the pnictogens (Nitrogen group)) have electron configura... |
I'm reading document about Solid phase protein synthesis (SPPS) from [Wikipedia](https://en.wikipedia.org/wiki/Peptide_synthesis#Solid-phase_synthesis), and according to the document:
> SPPS is limited by yields, and typically peptides and proteins in the
> range of 70 amino acids are pushing the limits of syntheti... |
Why is solid phase peptide synthesis limited to 70 amino acids? |
The book's explanation about a noble gas configuration is somewhat accurate, but fairly incomplete.
The elements on the right and on the left of the periodic table (the alkali (earth) metals, the halogens, the chalcogens (the group that starts with Oxygen) and the pnictogens (Nitrogen group)) have electron configura... |
Are aqueous solutions of oxidizing agents safe? |
The book's explanation about a noble gas configuration is somewhat accurate, but fairly incomplete.
The elements on the right and on the left of the periodic table (the alkali (earth) metals, the halogens, the chalcogens (the group that starts with Oxygen) and the pnictogens (Nitrogen group)) have electron configura... |
I bought a thermometer from Cole-Parmer having kerosene as the fluid, and the fluid is broken up. The fluid in the bottom part goes up to about 10 °C even though it is 20 °C in the room, then there is a gap followed by fluid between 23 °C and 25 °C, then there is no fluid going all the way to the top where there is ano... |
As an amateur soda maker, I have noticed an odd phenomenon: lemon juice sodas do not foam. Virtually every juice I have tried foams to some degree when mixed with carbonated water. Lemon juice does not. I have read "folk" explanations for this as being due to the "acidity" of the lemon juice, but this is not correct be... |
Lemon juice, the ultimate anti-foaming agent? |
Different sources have different answers. In the reduction of an aldehyde or ketone to an alcohol by Sodium Borohydride, how many moles of aldehyde are reduced by one mole of Sodium Borohydride?
While my teacher claims it is 1, Solomons-Fryhle claims it to be 4.
|
How many hydride ions are available in NaBH4? |
The classic paper of [Dr. Norskov](https://profiles.stanford.edu/jens-noerskov) explained this phenomenon very well. (Off topic: Dr. Norskov is like the godfather of catalysis and I had a chance to meet him at a summer school and that was a great experience for me.)
The inertness of metal surface to adsorb depends ... |
The first step toward answering this question is understanding the extent to which the statement "Group 11 metals are unreactive" is or isn't true.
As stated in [How do plants respond to copper deficiency?][1] *Plant Signaling and Behavior* vol. 3, pages 231-232:
> The transition metal copper is essential for a... |
> Is there a natural abundance threshold of a 'synthetic' element for it
> to be considered natural?
$\mathrm{> 0}$
In other words, any element that can be **detected** outside of the laboratory (*e.g.* in the natural environment) is a naturally occurring element. This would include the 80 stable elements along... |
Are my protolysis equations right? |
For the sake of the question, let’s assume that you are provided with two labelled rods of the pure metals $\ce{A}$ and $\ce{B}$ and two unlabelled bottles containing $1.0\ \mathrm{mol\ dm^{-3}}$ aqueous solution of $\ce{A^{$m$+}}$ and the other bottle containing $1.0\ \mathrm{mol\ dm^{-3}}$ aqueous solution of $\ce{B... |
For the sake of the question, let’s assume that you are provided with two labelled rods of the pure metals $\ce{A}$ and $\ce{B}$ and two unlabelled bottles containing $1.0\ \mathrm{mol\ dm^{-3}}$ aqueous solution of $\ce{A^{$m$+}}$ and the other bottle containing $1.0\ \mathrm{mol\ dm^{-3}}$ aqueous solution of $\ce{B... |
Dispersion of Lithium Ions in Nature (Ratio Similar to Isotopes?) |
One answer is that the ancient Greeks, specifically Plato, devised the term "element". Quoting from [wikipedia article on Classical elements](https://en.wikipedia.org/wiki/Classical_element#Greece):
> Plato seems to have been the first to use the term "element (στοιχεῖον, stoicheion)" in reference to air, fire, ear... |
What is the quickest way to dissolve a large chunk of steel? and I mean a very quick reaction, assuming that the interaction occurs in a sealed or semi-sealed environment? reaction times of the order of a few minutes versus tens of minutes, hours or days are the objective.
I'm curious as to how quickly acids like HN... |
Two to look up as "homework ". Aqua Regia which is a mixture that dissolves gold. Not good enough for engineering and some other rare earth metals. Steel? Maybe. The other is Caro's acid. There's a YouTube video of it dissolving a fly. That's organic matter so it may not be good enough for steel. Worth a look though. |
An alloy is a material composed of two or more metals or a metal and a nonmetal. And, they are usually formed by heating the elements to their melting points, and then cooling them, so that the components mix. Now, why doesn't this works backwards i.e. if we heat the alloy again to melting point of their constituents, ... |
If alloys are homogeneous mixtures, why can't we separate their components? |
What is the quickest way to dissolve a large chunk of steel? I mean a very quick reaction, assuming that the interaction occurs in a sealed or semi-sealed environment? Reaction times of the order of a few minutes versus tens of minutes, hours or days are the objective.
>I'm curious as to how quickly acids like $\ce{... |
What is the quickest way to dissolve a large chunk of steel? I mean a very quick reaction, assuming that the interaction occurs in a sealed or semi-sealed environment? Reaction times of the order of a few minutes versus tens of minutes, hours or days are the objective.
I'm curious as to how quickly acids like $\ce{H... |
What is the quickest way to dissolve steel? |
For the sake of the question, let’s assume that you are provided with two labelled rods of the pure metals $\ce{A}$ and $\ce{B}$ and two unlabelled bottles containing $1.0\ \mathrm{mol\ dm^{-3}}$ aqueous solution of $\ce{A^{$m$+}}$ and the other bottle containing $1.0\ \mathrm{mol\ dm^{-3}}$ aqueous solution of $\ce{B... |
How to identify which of two given electrodes with corresponding solutions is reducing more? |
I'm now learning about nomenclature. In particular, oxyanions.
Basically, when you have an anion that is a combination of a non-metal with oxygen.
According to my book:
> It ends with -ate for the most common oxyanions of the element. It
> ends with -ite for the oxyanions that have the same charge but with
>... |
When to use -ate and -ite for naming oxyanions? |
I'm now learning about nomenclature. In particular, oxyanions.
Basically, when you have an anion that is a combination of a non-metal with oxygen.
According to my book:
> It ends with -ate for the most common oxyanions of the element. It
> ends with -ite for the oxyanions that have the same charge but with
>... |
I want to know how to easily make the difference or just understand the importance of stereocenters of ephedrine ? |
What is the difference between threo/erythro ephedrine? |
The resin is made up from two components:
Component A: silicic acid, sodium salt (less than 10% sodium silicate)
Component B: Diphenylmethane-4,4'-Diisocyanate, isomers and homologs (MDI,Polymer-MDI)
It has been cured in place, however it became stuck to a piece of equipment made out of rubber. ... |
How to dissolve a strong resin in difficult situation? |
My textbook ([Organic Chemistry, 2nd Ed. Hornback, Joseph][1]) states that if a hydrogen is located near the center of an aromatic ring it will experience an (often quite sizable) upfield shift, as seen in these images (borrowed from aforementioned textbook)
Structure 1
![enter image description here][2]
Struc... |
I'd like to investigate into the ring opening, the migratory reverse reaction of the electrocyclic ring-closure of Dimethyldioxirane:
![enter image description here][1]
As a first question I'd like to ask if I have drawn the through bond interaction correctly?
![enter image description here][2]
Following sc... |
Is there any such thing as a twist chair conformation?
Also, the boat and the chair conformations are achiral, while the twist boat conformation of cyclohexane is chiral and dissymetric.
What about the half chair conformation? It has a plane of symmetry and is achiral (I wanted to confirm this; I haven't been able to... |
Is there any such thing as a twist chair conformation?
Also, the boat and the chair conformations are achiral, while the twist boat conformation of cyclohexane is chiral and dissymetric.
What about the half chair conformation? Am I right in thinking that it is achiral because it has a plane of symmetry? |
The anode region is on the iron where the following reaction occurs:
$$\ce{Fe(s) -> Fe^2+(aq) + 2e-}$$
and at the cathode region, the following reaction occurs
$$\ce{O2(g) + 4H+(aq) + 4e- -> 2H2O(l)}$$
However, the textbook does not explicitly state what the cathode region is. Can someone provide an answer? |
**You raise an excellent question and the short answer is "yes, quantum chemistry calculations are intrinsically in vacuum".**
Approximate methods like semiempirical (AM1, PM6, PM7) and hybrid DFT methods (e.g., B3LYP) use experimental data, which often comes from crystal structures.
For many years, single-crysta... |
I know that Gaussian assumes the molecule is alone in vacuum, that is, the molecule doesn't interact with anything, when optimising the molecule.
But I've found that Gaussian's optimisation(at HF or DFT levels) results are almost the same as experimental data, which were from the solid state by X-ray diffraction. E... |
**You raise an excellent question and the short answer is "yes, quantum chemistry calculations are intrinsically in vacuum".**
Approximate methods like semiempirical (AM1, PM6, PM7) and hybrid DFT methods (e.g., B3LYP) use experimental data, which often comes from crystal structures.
For many years, single-crysta... |
I have Stainless Steel welded to Titanium. I need a common etchant to etch both S.S. and $\ce{Ti}$ so that I can do further analysis (like SEM etc). Right now I'm etching Ti Side separately and S.S. side separately and doing analysis twice, once for each metal. The etchants I'm using are mentioned below:
1. $\ce{HNO... |
I want to make ferrofluid, which is ferromagnetic particles suspended in a carrier fluid. Three methods I have seen involve using magnetic ink (for MICR codes), cassette tapes, or ferric chloride as the iron source. The last method is the only one that makes ferrofluid with nano-scale ferromagnetic particles. AFAIK, th... |
Can I make Ferrofluid without evaporating Ammonium? |
This questions calls for an answer from thermodynamics.
![Phase diagram of carbon.][1]
The figure provided above, lifted from [here][2], is what we call a phase diagram. On the abscissa is temperature in units of Kelvin and on the ordinate is the pressure given in units of Gigapascals. (For your own reference, ... |
I was thinking about orbital angular momentum today and wondering how exactly do the numbers come about that quantize them. I was doing a little research on how they come about and I came across this image many times.  Is it feasible to get 0 $\ce{Cd}$ impurities in $\ce{Mg}$ precipitate by using $\ce{NaF}$ instead o... |
I'm trying to learn about ions. There is a slide with examples about combining cations with anions. It goes like this:
> $$\text{For} \ \ Al^{3+} \ \ \text{ and } \ \ O^{2-} \ \ \text{you get} \ \ Al_2O_3$$
Wait what? So you have an atom of Aluminum (in this case a cation because it loses 3 electrons) and an ato... |
This questions calls for an answer from thermodynamics.
![Phase diagram of carbon.][1]
The figure provided above, lifted from [here][2], is what we call a phase diagram. On the abscissa is temperature in units of Kelvin and on the ordinate is the pressure given in units of Gigapascals. (For your own reference, ... |
I'm trying to learn about ions. There is a slide with examples about combining cations with anions. It goes like this:
> $$\text{For} \ \ \ce{Al^{3+}} \ \ \text{ and } \ \ \ce{O^{2-}} \ \ \text{you get} \ \ \ce{Al_2O_3}$$
Wait what? So you have an atom of Aluminum (in this case a cation because it loses 3 electr... |
$$
\newcommand{\linop}[1]{\hat{#1}}
\newcommand{\ramuno}{\mathrm{i}}
\newcommand{\ket}[1]{\,|{#1}\rangle}
$$
Classical Mechanics
===================
In classical mechanics, the *angular momentum*, $\vec{L}$, of a particle with respect to a chosen origin is given by the vector product of its position vector r... |
I'm trying to learn about ions. There is a slide with examples about combining cations with anions. It goes like this:
> $$\text{For} \ \ \ce{Al^{3+}} \ \ \text{ and } \ \ \ce{O^{2-}} \ \ \text{you get} \ \ \ce{Al2O3}$$
Wait what? So you have an atom of Aluminum (in this case a cation because it loses 3 electron... |
I would like to help here, but I am not sure where to begin. First of all, I want to point out that the reaction you have shown is not an electrocyclic reaction, because it does not involve the central saturated carbon atom. It is rather a simple homolysis reaction. The terms "conrotatory" and "disrotatory" are misappl... |
Some substances like copper sulfate for example have vivid colors. But why is water transparent? Does it not emit any visual light from the electromagnetic spectrum? |
Why are (non-polar) hydrogen atoms generally neglected in a protein-ligand (or drug) binding energy calculation? They do have charge and mass. Doesn't that affect the free energy calculation?
The relevant equations are given here:
$$ \Delta G_\text{bind} = -RT\ln K_\text{d} $$
$$ K_\text{d} = \mathrm{\frac{[Recept... |
Why are non-polar hydrogens neglected in computational protein-drug binding studies? |
> Why do compounds form bonds? I've got three words for you: Less potential energy. I don't remember a case of positive lattice enthalpies $\ldots$ - [My comment](http://chemistry.stackexchange.com/questions/32980/about-combining-a-cation-and-an-anion?noredirect=1#comment49024_32980)
This makes me wonder. I remember... |
Can positive lattice enthalpies during the formation of ionic compounds exist? |
Can negative (abnormally) lattice enthalpies during the formation of ionic compounds exist? |
Having a real pain with nomenclature. Look at this substance:
$$MnO_4 \ ^{-}$$
So, we got an anion of Manganese and Oxygen (or is that just an anion of Oxygen?).
Anyway, my book says that $MnO_4 \ ^{-}$ is "Permanganate".
Since it ends with -ate, it seems my book thinks $MnO_4 \ ^{-}$ is an Oxyanion (becaus... |
Nomenclature of $MnO_4 \ ^{-}$: is it an oxyanion? |
Having a real pain with nomenclature. Look at this substance:
$$\ce{MnO_4^{-}}$$
So, we got an anion of Manganese and Oxygen (or is that just an anion of Oxygen?).
Anyway, my book says that $\ce{MnO_4^{-}}$ is "Permanganate".
Since it ends with -ate, it seems my book thinks $\ce{MnO_4^{-}}$ is an Oxyanion (... |
Nomenclature of MnO4 -: is it an oxyanion? |
> Why do compounds form bonds? I've got three words for you: Less potential energy. I don't remember a case of positive lattice enthalpies $\ldots$ - [My comment](http://chemistry.stackexchange.com/questions/32980/about-combining-a-cation-and-an-anion?noredirect=1#comment49024_32980)
This makes me wonder. I remember... |
The synthesis you are referring to is outlined [here](http://www.orgsyn.org/demo.aspx?prep=CV2P0264). Potassium Carbonate acts as a drying agent as you said as the later part of the distillation requires a specific temperature to remove the toluene and alcohol.
The water comes from the concentrated sulphuric acid so... |
Recently I did a distillation. At a certain point an azeotropic mixture of alcohol, water and toluene evaporated and was caught in a beaker with anhydrous potassium carbonate. I had to shake it and then pour it back into the reaction mixture (while filtering out the solid).
Why did I have to catch it in a $\ce{K2CO... |
Potassium carbonate and water/alcohol/toluene? |
Lets state my assumption that we can represent the free energies of the mixtures in fairly regular thermodynamics of phases ways (as I will get to here quickly). I will also assume fairly limited solid solubilities (think something like the Au-Si system).
OK, just take a system of A and B. The Gibbs free energy of a... |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.