# All Questions

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### What makes a molecule a polyatomic ion?

I checked the Wikipedia page, but it did not seem to provide a very intuitive explanation. What distinguishes a molecule such that it behaves like a polyatomic ion? I understand that it is a ...
3k views

### Why doesn't water play a role in reactions in aqueous reactions?

$$\ce{Ba(NO3)2(aq) + Na2CO3(aq)}$$ In the above reaction both the substances are in water, however water plays no role in the reaction. Why is it that although water is present in the reaction, it ...
4k views

### Is “ice point” the same as “freezing point”?

I am using an old book and they almost use both terms interchangeably sometimes. Do they mean the same thing? Similiarly for "steam point" and "boiling point"
600 views

### Why is it called “carbonation”?

Why is it referred to as "carbonation" and we drink "carbonated" beverages when carbonate is $\ce{CO3}$ while $\ce{CO2}$ (carbonite?) is present in carbonation?
1k views

### Is there a similar characteristic of the lanthanide contraction in the other transition metal groups?

Basically, does the lanthanide contraction also occur with the 4d, 6d groups as well? I am at a lack of understanding in this topic, I am just wondering what specific elements does this jump in a ...
5k views

32k views

### Why is water a dipole?

Water ($\ce{H2O}$) is a dipole. The reason why is simply because it is not symmetrical, there are more electrons on the oxygen side than on the hydrogen side, and the electronegativity of oxygen. But ...
3k views

### How to extract pure caffeine from tablets?

I have some caffeine tablets and I want to extract the pure caffeine from the rest of the ingredients (caffeine 200 mg. Inactive ingredients in order are corn starch, dextrose, dicalcium phosphate, D&...
1k views

### Why must an oxidizer not touch rubber?

Why is it that oxidizers (specifically $\ce{KClO3}$) are at risk of causing a fire when they come into contact with the rubber stopper used to contain them in their container, but can be slowly heated ...
58k views

### Calculating the heat capacity of a calorimeter

I've been struggling with this problem that I can't seem to figure out. I think I know how to solve it but I think there's missing information. The combustion of 1 mole of glucose $\ce{C6H12O6}$ ...
1k views

### What determines the electronegativity of an element?

Is it possible to work out without post-Bohrian mathematics?
5k views

### Inherent error in mass and volume?

In one of my chem classes I had to do a lab that involved finding the mass and volume of a substance. I did three trials and for my mass I got 9.3g, 9.3g, and 9.4 g. For my volume, I got 9.7ml, 9....
222k views

### Will alcohol or soap damage plastic or rubber?

I have read conflicting advice on various sites about the appropriate methods for cleaning plastic and rubber items and would like to ask people who actually know what's going on what they would ...
231 views

### What is the 'ancestral term' in the LS coupling scheme?

On the physics.nist.gov site: http://physics.nist.gov/Pubs/AtSpec/node06.html The table titled "Atomic structural hierarchy in LS coupling and names for the groups of all transitions between ...
452 views

### multielectron spin-orbit coupling and energy level

For multi-electron atoms for which the Hamiltonian (including the spin-orbit coupling) reads $$H=\sum_i T_i-Z\sum_i V_i+\sum_i V_i^{\text{s.o.}}+\sum_{i>j}V_{ij}$$ The $T_i$ are the kinetic ...
1k views

### Is there an alternative to the half-reaction method to solving red-ox reactions?

The equation for the reaction between a permanganate and iron(II) ions in acidic solution is: $\text{MnO}_4^- + \text{Fe}^{2+} \longrightarrow \text{Fe}^{3+} + \text{Mn}^{2+}$ My book, as well as a ...
501 views

### Can molecules diffuse upstream when emptying a cup of tea?

I was drinking some tea, and I randomly decided to pour some into the toilet in an unbroken stream; can particles travel "upstream" quickly enough to reach the mug of tea? How fast can diffusion occur ...
3k views

### Is there any scenario in which the size of a molecule increases due to an increase in temperature?

Take an ice cube for example. Heat is applied in a closed container until it is vaporized completely. Will the molecule's size be larger (on average)? Is there a substance that you know of that has ...
844 views

### Do dishwashing detergent and stain remover powder/stick have the similar ability to remove collar rings?

For yellow rings on shirts caused by skin grease or sweat: Some recommended to use an "Oxyclean" stain remover or stain remover stick for cleaning. Some recommended to use dishwashing detergent to ...
183 views

### Are words on my T-shirt removable? [closed]

I wonder if the words on my T-shirt are removable? If yes, what kind of (chemical or physical) ways are there? They look like paints on the cloth, as the letter "C" has become blurred in the way ...
147 views

562 views

### Product/(s) of the following reaction

I was wondering what the product will be in the following reaction: $$\ce{H3COOCH3 ->[\ce{H+}]} \:?$$ I was thinking about $\ce{CH3COOH}$ being a product but I do not know the mechanism.
6k views

### Reaction between potassium permanganate, alum, and sodium hydrogen sulfite

When I was a teenager, I played with a chemistry set. I tried adding potassium permanganate, alum, and sodium hydrogen sulphite (not sodium hydrogen sulphate) to water. Upon adding the third ...
104 views

### Methods: Does failing at intermolecular properties mean the same for intramolecular properties?

Let us consider the following: 1.) Method X fails at describing intermolecular non-covalent interactions. 2.) Method X excels at describing molecules of type Y. 3.) Method X ___?___ at describing ...
173 views

### Why would the loss of H₂ to space mean that the Earth's geochemistry would be based on acid/base reactions?

I am reading a paper[1] that contains the line: Most of the $\ce{H2}$ in the Earth's mantle escaped to space early in the Earth's history; consequently, the overwhelming majority of the abiotic ...
37k views

### Oxidation number for nitrogen in ammonium sulfate [duplicate]

I'm trying to find the oxidation number of $\ce N$ in $\ce{(NH4)2SO4}$. The answer is supposed to be $-3$ but I can't figure out the logic behind this.
8k views

### What is 'autogenous pressure'?

Compound 1 was hydrothermally synthesized under autogenous pressure[1] I've seen this term used a few times, but with no real explanation of what it means forthcoming. I suspect it refers to the ...
34k views

### What is the chemical structure / hybridization of sulfuric acid?

I was looking at the chemical structure of $\ce{H2SO4}$. Intuitively, I would have expected this molecule to be square planar in accordance with $p^2d^2$ or $sp^2d$ hybridization, but instead it is ...
2k views

### Why does cesium have a positive electron affinity?

When an electron is added to cesium, why is energy released?
203 views

### Modeling perturbations of a quantum mechanical system

I'm wondering how to properly perturb a quantum mechanical system. I'm looking for a way to express the return to equilibrium of such a perturbed state, where the perturbation is in the Hamiltonian. ...
1k views

### Very slow chemical clock reaction

I'd like to preface this with a declaration of my understanding that this is not necessarily possible. I was wondering if anyone knew of a chemical clock reaction where the period before the first ...
4k views

### Modern alternatives to Gaussian [closed]

Specifically, I'm curious if there are any programs which come close to Gaussian in breadth but also take advantage of things such as GPU processing. There's a page on wikipedia that goes through ...
295 views

### Spectral analysis of periodic table of elements in time domain

I'm trying to get the spectral analysis data of the periodic table of elements in the time domain format or find a site that has the data in the time domain format. All the sites I know have the data ...
2k views

### Is there a simple way to get the circular dichroism of a molecule from its structure?

Are there any heuristics to get the relative absorbtion of left and right circularly polarized light by a molecule from its molecular structure? Is it even possible to predict which polarization is ...
105 views

### What legal guidelines exist for completeness of a Materials Safety Data Sheet?

I know that the answer to this question will vary by country, but some aspects must be similar amongst those countries that have authorities overseeing chemical and industrial hygiene. The Wikipedia ...
10k views

### Can acidic conditions break disulfide bonds

I am denaturing a protein using organic solvent and acid (49:49:2% water:methanol:acetic acid), but I want to maintain the disulfide bonds. My chemistry knowledge isn't good but disulfides are broken ...
2k views

### Why don't atoms with expanded valence shells have a formal charge?

I'm working through Chemistry - Principles and Practice, 3rd Edition and I have few complaints so I don't think it's the text. At one point, I was asked to draw the Lewis structure, with formal charge,...
20k views

### How to properly dispose of sodium…or store it properly

While performing an inventory of my school's chemical storage closet today, my fellow teacher and I found some sodium tucked away in the back corner of our flammables cabinet. One container appears ...
3k views

### Which of the following possesses the highest energy electron?

Which of the following possesses the highest energy electron? $\ce{Br-}$ $\ce{Ca^2+}$ $\ce{Cr+}$ $\ce{As}$ Don't bromine and arsenic have equally high energy electrons (i.e. in ...