# All Questions

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273 views

### Crystallization from a solution

I was wondering if there is any other way to crystallize materials from a solution other than using supersaturation? Thanks,
821 views

### Parts of a manometer

There is a poor quality photo in the diagram of a manometer below: The picture is too poor for me to understand what they mean by "glass pointer marks calibrated volume". I would be interested if ...
4k views

### What is the substance in the new water cooler filter that give bubbles and taste a bit like soap

Recently the water cooler was replace with a new filter. However, when I refill my water kettle with the water from the water cooler, there are many bubbles and the taste was a bit like soap. What ...
1k views

### Forms of Henry's law versus ideal gas law

This might be a slightly daft question as I'm a physicist rather than a chemist, but I have a slight problem in using Henry's law which I think I can circumvent using the ideal gas law – I'd be ...
8k views

### How does the volume of a mole of ideal gas relate to pressure and temperature?

The volume of a mole of gas is: $\ce{22.4 l}$ directly proportional to pressure and Kelvin temperature. directly proportional to pressure, inversely proportional to Kelvin temperature. inversely ...
718 views

### Why can't you see air but can feel it [closed]

Is there a device that can measure the air in the room in lbs? I would appreciate the anseer
25k views

### Why won't water freeze if you put ice in it, despite ice being frozen?

Just now I got some room temperature water and added some ice to cool it, and it just came to me, like the scientist I wish I was ... why doesn't frozen (freezing point) ice added to higher ...
270 views

### Can I perform a stable isotope analysis at home?

I'm interested in measuring the stable isotope ratios of some bird feathers. I'm aware that a mass spectrometer is required to measure stable isotope ratios. Is it possible to measure stable isotope ...
14k views

### Are there substances that cannot undergo combustion?

Are there substances that cannot undergo combustion? If so, what are they?
3k views

### How do you calculate the absorption spectrum of water?

If you look online you can find various graphs of the absorption spectrum of water. The graph below for examples comes from this blog post. As far as I can tell these graphs come from empirical ...
12k views

### Oxidation State in Tetraaquadichlorochromium(III) chloride

$\ce{[Cr(H2O)4Cl2]Cl}$, Tetraaquadichlorochromium(III) chloride According to a book, the (III) indicates the oxidation state of chromium, but it doesn't explain why. Cr has 6 valence electrons. How ...
7k views

### How many valence electrons does the azide ion have?

We had a test and and we had a question asking the number of valence electrons in an azide ion, $\ce{N3^{-}}$. I find out that the answer is 16 but I could not understand how. I saw the structure. ...
14k views

### Why is methyl group more electron-donating than tert-butyl group?

As title says, why is methyl group more electron-donating than tert-butyl group? The context behind this is stabilization of conjugate base. (http://www.khanacademy.org/science/organic-chemistry/...
38k views

### Why do molecules having a higher relative molecular mass have stronger inter-molecular forces?

Why do molecules like alkanes with higher relative molecular mass ($M_\mathrm r$) have stronger intermolecular forces? For example, methane ($\ce{CH4}$) has a weaker intermolecular force than pentane (...
54 views

### What does $\mathrm{A}_r(\mathrm{H})$ represent when calculating the average natural weight of an elemental atom?

I have a question that explains the weights and abundances of various hydrogen isotopes, and the question concludes by asking to: Calculate the atomic mass of hydrogen $\mathrm{A}_r(\mathrm{H})$ (...
962 views

### Do chemical compounds have spectral lines, or only elements?

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 ...
6k views

### Assay over 100% (L-Cysteine Hydrochloride Monohydrate)

In reading a COA (Certificate of Analysis), I came across an Assay line: The Assay is 100.5% where "Lower Limit" is 98.5 and "Upper Limit" is 101.0 This product ...
3k views

### Is there a word for a compound that has both ionic and covalent bonds?

For example, calcium carbide (CaC$_2$) has covalent C‒C bonds and ionic Ca$^{2+}$‒ C$_2^{2-}$ bonds.
10k views

### Can you heat water with additives?

I have been curious about this question for a while. If you want to warm up a large amount of water, is it feasible to do this by adding a substance that has an exothermic reaction with the water? ...
77k views

### How do I chill water without a refrigerator?

How can we chill water in a plastic bottle without a freezer or refrigerator? Scenario: I'm in the office and I have two plastic bottles of water (brought from home). I'm in the office for 3 to 4 ...
2k views

### Can dust or fingerprints interfere in ultra-violet spectroscopy

My question pertains generally to any form of spectroscopy, but I'll focus on UV spectroscopy. I am trying to get information on carrying out spectroscopy, but most of it is theoretical. Wikipedia is ...
223 views

### How does pressure shift equlibrium

Here is a question from my practice problems: I know that the answer is A, but I don't know why. Is it because A has the most moles of gas on the left? thanks
332 views

### Air recycling system(CO₂-->O₂) or (CO₂-->fuel)?

I'm not a chemist but I'm working on an eco-friendly project that is supposed to recycle $\ce{CO2}$ from the air and convert it to $\ce{O2}$ or at least a usable fuel source ,the system can use the ...
2k views

### Acids that donate just one proton

What is the general name for acids that can only lose one hydrogen ion? (i.e. $\ce{HCl}$) What is the general name for acids that can lose $n$ hydrogen ions? (i.e. $\ce{H_3PO_4}$, which can lose 3) ...
230 views

### How many protons are required to satisfy hydroxyamine's (NH₂OH) lust for protons?

I ask because I'm trying to write an equilibrium equation for this reaction and I'm wondering whether an extra 2 protons will be required after one is taken to attack the $\ce{OH}$ group and turn it ...
6k views

### Liquid with low specific heat and high thermal conductivity (relative to water)?

As the title suggests – does there exist a liquid with a lower specific heat then water but with a higher thermal conductivity? I thought of this in the context of sous vide cooking: Ideally, the ...
3k views

### Flame temperature for cooking food

Which has hotter temperature, blue flame or yellow flame?
1k views

### Why is Lanthanum a "fluoride ion sensitive electrode" and hence used for measuring "flouride concentration"?

My chemistry text book says that "Atomic Absorption Spectrometry (AAS) can be used to determine the concentration of metal ions, but other methods must be used for anions. One convenient method is to ...
203 views

### Helium empirical wavefunctions

I know that analytic forms of the Helium wavefunctions are not known. However, are there empirical expressions for the low-lying states of Helium? I'd like to use them to calculate some transition ...
39k views

### Valence electrons in helium?

I am having trouble understanding how valence electrons are counted in Helium. My references are: Here where it appears that Helium has 0 valence electrons because the shells are finished Here ...
148 views

### Transition Metals' Charges

I came across a compound $\ce{[FeO4]^{2-}}$ but $\ce{Fe}$ has +6 charge according to my calculations. How this is possible ? Or it is possible but my periodic table is kind of non-detailed one. (On ...
20k views

### Why is a theoretical titration curve higher than a practical one?

I'm currently in high school and I did two titrations. The first one is a titration of $10.0~\mathrm{mL}$ $0.1~\mathrm{M}$ $\ce{HCl}$ with $x~\mathrm{mL}$ $\ce{NaOH}$. I obtained the following ...
254 views

### How do chemists decide on which detergent to use?

I found betaine in my face wash. I think it is there because it has a hydrophobic (non-polar) end that can pick up grease, and a hydrophilic (polar) end that means it is attracted to polar solvents, ...
23k views

### The influence of lemon juice & sugar on the ph-value

If I add equal amounts of lemon juice and sugar into water, does the ph-value remain unchanged, as both cancel each other out? This question arose in my head as I learned that pouring milk into ...
760 views

### Geometrical Isomerism of Metal Complex

Does $\ce{Ni((en)2(Cl)2)}$ show cis-trans form ? And if No Why not ?
1k views

### What tools are used to predict the products of a chemical reaction? [duplicate]

I was wondering if there is a decent and non-complex way to predict the outcome of mixing two chemicals together. I know that molecular dynamics is used in computational chemistry to understand ...
3k views

### What is the accuracy of scf=qc when convergence criteria is lowered?

I am trying to run single point calculations with Gaussian 09 for a Mulliken population analysis on large graphene/graphite (940-1411 atoms) sheets/clusters. I was having difficulty with memory ...
7k views

### What's the physicochemical difference between a chromophore and a fluorophore?

Let's take Hematoxylin, which is a pH indicator and a stain for histology, and therefore a chromophore, but does not fluoresce: Now let's take Eosin, which stains tissue pinkish, but is also ...
2k views

### Avogadro - How can bonds be hidden and only show atoms?

I am using Avogadro for visualizing some cluster systems. Is there a way to hide the bonds of the system, ie. only showing atoms? Thanks!
153 views

### chemical equilibrium reaction for burned gases in engine

I do not understand how equation(3) occurs.(taken from the book Internal Combustion Engines by John B.Heywood)  Consider a reactive mixture of ideal gases. The reactant species $M_a,M_b$ etc.and ...
140 views

### How did Scientists Capture The First Images of Molecules Before and After Reaction?

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 ...
3k views

### Open Source tools to draw a set of 2d molecular graphs from sdf file

I have a sdf file for around 50 small-molecules for which I am doing structure-activity study. I would like to draw 2d graphs of all the molecules such that the image would fit into a single journal ...
1k views

### Nomenclature of alkenoic acids - which group has priority: the alkene or the acid?

Right, how do you systematically name them? Also, do you number them from the double bond end or the Carboxyl end? Ie would it be something like. 2-methyl Hept-3-enoic acid? Scuse the bad question ...
602 views

### Create my own solar cells?

How would I grow my own and build functional solar cells? I've read and researched that they're mostly a crystal structure of something like silicon. I would assume I'd be able to grow my own crystals ...
2k views

### What is a "Strong" Acid?

If a reaction requires a "strong" acid - what does this mean? Does it mean any acid of a specific concentration or pH? Are only certain acids classed as "strong"? I have read on Wikipedia that it ...
3k views

### Finding Pv in Pv=nRT for molecular hydrogen

I'm attempting to write a small program that will calculate the values for the Ideal Gas Law, specifically for molecular Hydrogen (H2) in space. Eventually, this will grow to be a sort of "simulator",...
130 views

### How do the differences in the number of protons result in such great differences in elemental properties?

I understand(I think) the mass and density aspect, i.e. the more protons you have, the more the element weighs, also the denser the atom is. What about everything else(color, for example)? Elements ...
334 views

### FCI implementation

Could you suggest, please, a manual/textbook/tutorial for implementing FCI (full configuration interaction) method on computers. I am interesting in algorithms mainly. I would like to write my own ...