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Dissolving MnO2 with HNO3 [Mar. 6th, 2011|11:14 pm]
Chemistry Help

I ask a lot of questions and you all are always very helpful. (:

We recently had a lab where we used diluted HNO3 to clean a filter that we had collected MnO2 from. Why was HNO3 used when MnO2 is insoluble in nitric acid?

Someone showed me this reaction:

2MnO2 + 4HNO3 -> 2Mn(NO3)2 + 2H2O

which does not make sense to me since Mn(IV) is being reduced to Mn(II), but I don't see anything being oxidized. What am I missing here?

Thanks in advance for any help/insight.
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Buy Dehydrated Water! [Feb. 25th, 2011|02:46 pm]
Chemistry Help


Click in the "Media" tab. The dateline ("PASADENA, CA")is the location of Cal Tech.
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NaNH2 [Dec. 6th, 2010|05:36 pm]
Chemistry Help


Show the resonance intermediates formed when sodium amide reacts with p-chloronitrobenzene to form p-nitroaniline. Be Complete.

I'm confused. Will an elimination occur with the presence of NaNH2 (to give a benzyne intermediate) or will the NH2- anion initiate nucleophilic aromatic substitution? If substition occurs, why that over elimination?

Thank you!
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Chlorate Lewis Structure [Nov. 27th, 2010|04:02 pm]
Chemistry Help
What's the correct Lewis Structure for chlorate? My question is:

19. The Lewis structure for a chlorate ion, ClO3-, should show ____ single
bond(s), ____ double bond(s), and ____ lone pair(s).

My answer was 2 single bonds, 1 double bond, and 9 lone pairs but the correct answer is

3 single bonds, 0 double bonds, and 10 lone pairs.

In the Lewis Structure I drew, Cl has a formal charge of 1 and the double bonded O has a formal charge of 0. The other two O's have a formal charge of -1, which all adds up to -1 (the charge of ClO3). Can someone help me figure out where I went wrong?
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complex ion? [Nov. 20th, 2010|01:15 pm]
Chemistry Help

[mood |confusedhuh]

Dear all


What is the value of n?

I believe it's a square planar, and central atom would be I. I is from group VII, hence, 7 electrons around it. So since there are 4 fluorines, each would share 1 electron with iodine. Which leaves 3 lone electrons, ie, n = 3.

However, answer key says n = 1. Why is that?
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pH Changes [Oct. 14th, 2010|03:42 pm]
Chemistry Help

I have a homework problem that I don't quite understand how to explain. The problem states "Would the pH of a 1.100M solution of HCl change if 1.0 mole of NaCl is added to 1.0L of the solution?" I'm pretty sure that the pH won't change, and if it does, it isn't significant since NaCl is generally neutral in pH value...
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Application of Hess's Law [Oct. 12th, 2010|07:49 pm]
Chemistry Help
Sorry if this posted twice or something weird happened, my internet crashed at the most inopportune moment!

One of my homework questions is:

"Calcium metal will react in water to form calcium hydroxide, Ca(OH)2. Use the thermochemical data that follow and Hess's Law to calculate the value of ΔH° for the reaction

Ca(s) + 2H2O(l) = Ca(OH)2(s) + H2 (g)

a. H2(g) + ½O2(g)= H2O(l) ΔH°= -286kJ
b. CaO(s) +H2O (l) = Ca(OH)2(s) ΔH° = -64kJ
c. Ca(s) + ½O2(g)= CaO(s) ΔH°= -635kJ "

I know to flip line a and change the sign to a + 286 kJ. I was wondering why I didn't have to multiply line b by 2 because in the reaction H2O has a coefficient of 2.

Any help will be appreciated! I seem to be incompetent when it comes to Hess's law.
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what is different? [Oct. 3rd, 2010|03:05 pm]
Chemistry Help


I'm a curious chem newbie!

I have a simple question:

Say you've got 2-methyl-hexane and 3-methyl-hexane. Are these different alkanes? I think yes, but I'm not sure, since the formula is the same.

If I have 2-methyl-alkane and a 2-methylalkane that folds differently from the first one, are they different? (I don't know if this happens with simple molecules like this, but in theory...)
I would think yes, because different shape = reactivity would be different, right?

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Basic question [Oct. 2nd, 2010|03:25 pm]
Chemistry Help

I've been digging around the internet for a while, and I don't know if I'm blind, or something, but I can't find the standard reaction equation of butanoic acid and water. Is it a 1-1 ratio or something?
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Diluting solutions help [Oct. 1st, 2010|07:39 pm]
Chemistry Help
Sorry to post again! This one question on my homework has been bugging me for days. The question is:

Adding antifreeze to aqueous automobile cooling systems lowers the freezing point of the resulting solution. the main ingredient in most antifreeze products is ethylene glycol (C2H6O2). How many kilograms of ethylene glycol are dissolved in a 10.0-liter solution that is 16.0 M?

I am pretty sure I would have to use the M1V1=M2V2 formula. I just don't know what value I would have to put in for M1. Any hints whatsoever would help me greatly. Thanks in advance!
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