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1. ## 4 transformation questions

Have you tried working out any of these synthesis problems on your own yet? If so, please show us what effort you have tried putting into solving these questions
2. ## EZ heat

Sodium acetate (plus a bit of water) requires heat in order to go from a solid state to a liquid. During this time, the sodium acetate "stores" the energy. In addition, the liquid state is remarkably stable, even well below the point of crystallization (which is around 50C, I forgot the exact temperature). When you flex the metal disc, which contains a small bit of sodium acetate, crystallization occurs, and the heat that was stored up is released.
3. ## Geesh, I'm puzzled!

I can give you a hint for you to start, but won't give you a direct answer, you'll have to try yourself. I am surprised that a textbook that asks these type of questions does not cover it somewhere. Use your normal equilibrium setup, and equate that to your given Ka value in order to solve for the H+ concentration.
4. ## Electron Affinity

Potassium and lithium have relatively weak electron affinities, when compared to elements such as fluorine and chlorine. This is electron affinity (EA) is, as you sad, the "desire" of atoms to have a complete set of electrons. Elements like potassium and lithium would much rather give up that extra electron than to gain 7 more; atoms like fluorine would much rather gain 1 more electron to have a set of 8 rather than lose 7 electrons. In general, EA increases from left to right (high electron affinity at the right hand side), and decreases from top to bottom (high electron affinity at the top of the periodic table). Left to right sees an increase in electron affinity due to the atoms gaining closer to 8 electrons in their outer shell, while top to bottom sees a decrease because the electron orbitals are further away from the positive nucleus.
5. ## Mol Problems

Hint: All gases take up 22.4 L / mol, regardless of the gas (at least assuming this is at STP) Also, chlorine gas is Cl2, not 2Cl
6. ## Chirality?

Chirality is essentially when two molecules are mirror images of each other. They are non-superimposable. Using carbon as an example, a molecule such as CH4 cannot be chiral, as you can rotate it any which way, and it will still be superimposable. However, a molecule of (say) CFBrCl and its mirror image will be non-superimposable, causing it to be chiral. In the citronellol case, essentially, you are looking for a carbon molecule that has 4 different substituent groups. If you take the entire citronellol molecule and mirror it, you will have the other enantiomer.
7. ## Help!!!

For sulfuric acid, note that you have 2 hydrogen molecules, not just 1. For the ammonia, your addition is incorret (14 + 3 does not equal 15).
8. ## Limiting reagents

I'm going to assume it's balanced, from a quick glance, it does appear so. Take the masses you have of each, convert them to moles. Then, when they are in moles, you can simply use the numerical ratios in the balanced equation to figure out the moles of ammonium nitrate that will be formed.
9. ## rate of reaction?

Essentially, the higher temperatures will give energies more molecules, shifting them to the right of the Boltzman distribution.
10. ## pl help

Actually, sodium and potassium both will more readily give up that s orbital electron, rather than gaining one...remember the stable octet "rule" (not really a rule, more of a guideline, as there can be cases where atoms have more than an octet of electrons)
11. ## the reaction of copper wire and a flame

I should rephrase: what I meant to say is that these forums can be used as a tool to help people with their homework. However, at least in my opinion, they should not be used with the expectation for other users to complete homework for you.
12. ## the reaction of copper wire and a flame

Yes, that is the reaction, it will produce what woelen listed above. Also, this isn't a homework help forums, I believe the best way to learn is to not spoonfeed you answers.
13. ## Stoichiometry

Just so you're aware, this answer is also incorrect, as the equation is not yet properly balanced.
14. ## Stoichiometry

Firstly, write out the balanced chemical equation. Next, you would normally calculate the number of moles of your given starting reagent, however, since you already have the moles of hydrogen sulfide, you can skip this step. Once you have everything in moles, you can compare directly using the stoichiometry in your balanced chemical equation. I'm trying to be as clear as possible, but without giving away the answer here, though your answer of 145 moles of O2 is incorrect. Indeed, often if one substance is in excess, another will be the limiting reagent.
15. ## Electron Orbitals

Looks correct
16. ## Copper PCB vinegar etching

I agree with woelen, using vinegar could take days (maybe even weeks) before your PCB are etched significantly. Using ferric chloride would be the easiest way, no special equipment is necessary, a plastic tray of even a glass casserole dish would be fine.
17. ## Strontium Nitrate from Strontium Carbonate

This is probably the easiest way, I was going to suggest this method as well.
18. ## Crustaceans

Here's the structure of chitin, source: Wikipedia. http://upload.wikimedia.org/wikipedia/en/6/66/Chitin_fixed.png
19. ## Oscillating reaction -- cool experiment

In general, oscillating reactions will show some colour change (be it red to blue, yellow to purple, colourless to coloured, etc) that will oscillate (go back and forth) between the colours. Very neat experiment Woelen! Can't wait to see the page on making KBrO3
20. ## Formaldehyde in Beer

I'm pretty sure it's lactic acid that causes muscle pains. Acetic acid in the body should be rapidly converted to acetyl-CoA, if my biochemistry memory serves me correctly.
21. ## Formaldehyde in Beer

Formaldehyde is not formed in the body when ethanol is oxidized. It is acetaldehyde that is formed, which is then oxidized to acetic acid (and can be incorporated into TCA as acetyl CoA, etc). Formaldehyde would only be formed when people drink methanol (and end up poisoning themselves)
22. ## To reduce fat from body

I don't see how this could work in any way. What are the credentials of this "doctor" on television? You should be more skeptical of what you see on television. Edit: If you still want to try...I'm pretty sure magnesium sulfate won't have too much harm on your body, though it might irritate your skin.
23. ## Helium melts !!?!?!?!?!

I'm just curious, chuinhen, did you mean that the curve is (near) parallel to the X-axis? In the link that insane_alien has linked, the curve is definitely not parallel (or near parallel) to the Y-axis
24. ## Density of water decreases with decreasing temperature. Why?

As far as I know it, water is the only substance that has a decrease in density when the temperature decreases. All other substances should have an increase in density when the temperature decreases. For example, at STP, nitrogen is a gas, and is not very dense when compared to something like liquid nitrogen. Liquid nitrogen exists at 77 K, so at low temperatures, its density increases (as it's a liquid now, and liquids are obviously denser than gaseous nitrogen). For these "normal" substances, as the temperature decreases, what occurs is that the molecules come closer together, as they do not have the energy to "fly away" from one another. In a solid, the molecules are quite close together, so you have more mass per unit volume (the definition of density). This means that the density is high. In a gas, the molecules have more energy to "fly away" so in the same unit volume, there will be less molecules and thus less mass. The density is then less. In water however, as temperature decreases, the density decreases as well, which is an unusual characteristic of this substance. Why this occurs, I'm not sure of though
25. ## Phosphorus rockets

I believe in most countries, phosphorus is a banned chemical to possess, as it can be used in illegal activities (not to mention that the white allotrope is incredibly toxic too). I would look at other alternative fuels for rockets.
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