Asked by Corey

This is part of a marathon problem, we have to identify the five compunds of H, N, and O described below. For each compound, I have to write a Lewis structure that is consistent with the information given.
a.) All the compunds are electrolytes, although not all of them are strong electrolytes. Compunds C and D are ionic and compund B is covalent.

b.) Nitrogen occurs in its highest possible oxidation state in compunds A and C; nitrogen occurs in its lowest oxidation state in compunds C,D, and E. The formal charge on both nitrogen in compund C is +1; the formal charge on the only nitrogen in compund B is 0.

c.) Compund A and E exist in solution. Both solutions give off gases. Comercially available concentrated solutions of compund A are normally 16 M. The commercial, concentrated solution of compound E is 15 M.

d) Commercial solutions of compund E are labeled witha misnomer that implies that a binary, gaseous compund of nitrogen and hydrogen reacted with watert to produce ammonium ions and hydroxide ions. Actually this reaction occurs to only a slight extent.

e) Compound D is 43.7% N and 50.0% O by mass. If compound D were a gas at STP, it would have a density of 2.86 g/L.

f) A formula unit of compund C has one more oxygen than a formula unit of compound D. Compounds C and A have one ion in common when compound A is acting as the strong electrolyte.

g) Solutions of C are weakly acidic; solutions of compound A are strongly acidic; solutions of compound B and E are basic. The titration of .726 g of compound B requires 21.98 ml of 1.000 M HCl for complete neutralization.

This is due tomm and I have no idea what the question is asking or how to start.
Answered by DrBob222
Start with e).
You know N is 43.7%, O is 50.0%, so H must be 100% - those two. Calculate the empirical formula from this. Knowing the density of 2.86 (if it were a gas) calculate the molar mass, then determine the molecular formula.

Now go to f).
g) should give you the molar mass of comound B.
The rest of it then falls into place.
Post your work and we can go from here if you need additonal hints. (How long have you had this marathon problem if it is due tomorrow?)
Answered by Corey
Well i tried to get the empirical formula but i got H2NO, how do i use the density, 2.86.
Answered by DrBob222
H2NO is correct. Now if it were a gas (it isn't) the density would be 2.86. Remember that 1 mol of a gas occupies 22.4 L atr STP. So the molar mass of this material is ??. And that means the molecular formula is ??
Answered by Corey
I am not sure how to find the molar mass using the 22.4 L at STP
Answered by DrBob222
2.86 g/L x 22.4 L/mol = ??
Answered by Corey
So is H2NO correct?
Answered by DrBob222
No. What's the molar mass?
Answered by Corey
64.064 g/mol
Answered by Corey
the molar mass is 64.064 g/mol
Answered by DrBob222
Now what is the formula mas of the empirical formula you worked out? So now you know the molecular formula is ??
Answered by Corey
it should be H2NO3
Answered by DrBob222
Come on now. You have the molar mass correct at 64. You know the emprical formula is H2NO. So what is the formula mass of the H2NO (that's the emprical formula).All you need to do is add the atomic masses.
Answered by Corey
Ok so i am done with D
Answered by Corey
Because when i add the atomic masses i dont' get 64
Answered by DrBob222
You are getting ahead of yourself. What is the formula mass of the empirical formula. And what is the molecular formula. (Or tell me what you don't understand).
So what is D.
Answered by Corey
the formula mass is 32
Answered by DrBob222
Good. So if the formula mass is 32 and the molar mass is 64, that means the molecular formula must be ??
Answered by Corey
NH4NO2
Answered by DrBob222
VERY GOOD.
So D is NH4NO2. Now you know what C is? It is ??(from statement f)
Answered by Corey
C would be NH4NO3
Answered by DrBob222
RIGHT
Next I would go to statement g and work out the molar mass of compound B.
Answered by Corey
Ok but i am confused of how to use the info for B
Answered by DrBob222
mols cmpd B = L x M
mols = g/molar mass
Answered by Corey
I got the mols compound B = .002198 when i did the 21.98ml * 1M
Answered by Corey
Is this correct? the molar mass of B is 330.3
Answered by Corey
Hey i got the molar mass of B to be 330
Answered by DrBob222
Surely not. I think you have a decimal point off.
mols = L x M = 0.02198 L x 1.000 M = 0.02198
molar mass = g/mols = 0.726/0.02198= xx
Answered by Corey
oh ok my bad so the molar mass is 33.03
Answered by Corey
so now how do i find the formula
Answered by DrBob222
ok. Now you know the molar mass is about 33, you know from statement b that compound B has 1 N atom (with a formal charge of zero) AND from statement g that compound B is basic. So you need to put 1 N, an OH, and some H atoms to make 33.
Answered by Corey
would it be NH2OH
Answered by DrBob222
Probably, although you can't be definite about it with just a molar mass, 1 N, basic, and formal charge of zero. Those things fit but to be defnitive you would need an elemental analysis like you went through for compounds C and D.
OK.
Do you know the name of H2NOH?
Now you know B, C, and D. That leaves A and E. Not enough information is available about A or E to be definitive but you can make VERY good guesses about their identity.
Answered by Corey
would A be HNO3 and E be NH3
Answered by DrBob222
That's what I would guess. Statement c is a dead give away. I know HNO3 is sold commercially as 16 M solution and that NH3 is sold commercially as 15 M. Also, I know the bottle is labeled ammonium hydroxide and not aqueous NH3. So these probably are correct. The other statements are consistent with A and E being HNO3 and NH3.
I trust you can do the Lewis dot structures.
Answered by Corey
yes i can do them so i don't need to do any work for A and E?
Answered by DrBob222
Only to show that they are consistent with statements a, b, c, d, and g
Answered by Corey
Ok thanx alot i appreciate it
Answered by Anonymous
Dr. Bob yur a beast:]
Answered by jill
i had the same problem for ap chemistry and i looked at what you wrote but could you help me with it
Answered by Sarah
Whoever did this, thank you so much! You just saved my life on this problem and on my next test because it was extra credit and now I actually understand how to do it.
Answered by Jack
Thanks!
Answered by Tami
Thanks for working everything step-by-step! Truly appreciate it!
Answered by EIleen
so what is letter g?
Answered by Anonymous
gracias por el aporte
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