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Posted by on Wednesday, November 7, 2007 at 8:19pm.

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.

  • AP chem - , Wednesday, November 7, 2007 at 8:29pm

    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?)

  • AP chem - , Wednesday, November 7, 2007 at 8:41pm

    Well i tried to get the empirical formula but i got H2NO, how do i use the density, 2.86.

  • AP chem - , Wednesday, November 7, 2007 at 8:44pm

    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 ??

  • AP chem - , Wednesday, November 7, 2007 at 8:46pm

    I am not sure how to find the molar mass using the 22.4 L at STP

  • AP chem - , Wednesday, November 7, 2007 at 8:48pm

    2.86 g/L x 22.4 L/mol = ??

  • AP chem - , Wednesday, November 7, 2007 at 8:50pm

    64.064 g/mol

  • AP chem - , Wednesday, November 7, 2007 at 8:49pm

    So is H2NO correct?

  • AP chem - , Wednesday, November 7, 2007 at 8:49pm

    No. What's the molar mass?

  • AP chem - , Wednesday, November 7, 2007 at 8:50pm

    the molar mass is 64.064 g/mol

  • AP chem - , Wednesday, November 7, 2007 at 8:51pm

    Now what is the formula mas of the empirical formula you worked out? So now you know the molecular formula is ??

  • AP chem - , Wednesday, November 7, 2007 at 8:53pm

    it should be H2NO3

  • AP chem - , Wednesday, November 7, 2007 at 8:55pm

    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.

  • AP chem - , Wednesday, November 7, 2007 at 8:57pm

    Ok so i am done with D

  • AP chem - , Wednesday, November 7, 2007 at 8:58pm

    Because when i add the atomic masses i dont' get 64

  • AP chem - , Wednesday, November 7, 2007 at 8:58pm

    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.

  • AP chem - , Wednesday, November 7, 2007 at 9:00pm

    the formula mass is 32

  • AP chem - , Wednesday, November 7, 2007 at 9:01pm

    Good. So if the formula mass is 32 and the molar mass is 64, that means the molecular formula must be ??

  • AP chem - , Wednesday, November 7, 2007 at 9:03pm

    NH4NO2

  • AP chem - , Wednesday, November 7, 2007 at 9:05pm

    VERY GOOD.
    So D is NH4NO2. Now you know what C is? It is ??(from statement f)

  • AP chem - , Wednesday, November 7, 2007 at 9:06pm

    C would be NH4NO3

  • AP chem - , Wednesday, November 7, 2007 at 9:08pm

    RIGHT
    Next I would go to statement g and work out the molar mass of compound B.

  • AP chem - , Wednesday, November 7, 2007 at 9:10pm

    Ok but i am confused of how to use the info for B

  • AP chem - , Wednesday, November 7, 2007 at 9:12pm

    mols cmpd B = L x M
    mols = g/molar mass

  • AP chem - , Wednesday, November 7, 2007 at 9:15pm

    I got the mols compound B = .002198 when i did the 21.98ml * 1M

  • AP chem - , Wednesday, November 7, 2007 at 9:23pm

    Is this correct? the molar mass of B is 330.3

  • AP chem - , Wednesday, November 7, 2007 at 9:29pm

    Hey i got the molar mass of B to be 330

  • AP chem - , Wednesday, November 7, 2007 at 9:33pm

    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

  • AP chem - , Wednesday, November 7, 2007 at 9:35pm

    oh ok my bad so the molar mass is 33.03

  • AP chem - , Wednesday, November 7, 2007 at 9:38pm

    so now how do i find the formula

  • AP chem - , Wednesday, November 7, 2007 at 9:39pm

    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.

  • AP chem - , Wednesday, November 7, 2007 at 9:40pm

    would it be NH2OH

  • AP chem - , Wednesday, November 7, 2007 at 9:46pm

    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.

  • AP chem - , Wednesday, November 7, 2007 at 9:47pm

    would A be HNO3 and E be NH3

  • AP chem - , Wednesday, November 7, 2007 at 9:51pm

    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.

  • AP chem - , Wednesday, November 7, 2007 at 9:52pm

    yes i can do them so i don't need to do any work for A and E?

  • AP chem - , Wednesday, November 7, 2007 at 9:55pm

    Only to show that they are consistent with statements a, b, c, d, and g

  • AP chem - , Wednesday, November 7, 2007 at 10:21pm

    Ok thanx alot i appreciate it

  • AP chem - , Monday, January 28, 2008 at 6:24pm

    Dr. Bob yur a beast:]

  • AP chem - , Friday, December 31, 2010 at 11:25am

    i had the same problem for ap chemistry and i looked at what you wrote but could you help me with it

  • AP chem - , Wednesday, November 7, 2012 at 7:39pm

    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.

  • AP chem - , Monday, December 17, 2012 at 8:30pm

    Thanks!

  • AP chem - , Monday, November 11, 2013 at 3:24pm

    Thanks for working everything step-by-step! Truly appreciate it!

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