Strangely worded chem conversion.

[wanabe]

Determine the number of moles of N atoms in a sample of C_7 H_5 (NO_2)_3 that has the same number of O atoms as 13.4 g C_6H_12 O_6.

 

My first attempt 13.4 g C_6H_12 O_6(1mol C_6H_12 O_6/180.15768g C_6H_12 O_6)(6 mol O/1 mol C)=0.4462757291 mol O... since the values are equal I figured that the N would be the same; wrong!

 

(I know the masses of C_6H_12 O_6 are slightly different)

 

After some time I came up with 13.4 g C_6H_12 O_6(1 mol C_6H_12 O_6/180.1566g)(6 mol O/ C_6H_12 O_6)(6.022*10^23 atm/1 mol O)(3 mol N/6.022*10^23 atm)=1.33|8839672~1.34mol N... That however did not give the right results... Relating the number of atoms seemed strange to me but it seemed suitable for this question, as it reads: "the same number of O atoms". It seemed I could equate the N and O

 

Where have I gone wrong?

Edited September 19, 2010 by wanabe

[cypress]

By N atoms they mean Nitrogen atoms and while the number of Oxygens in each molecule is the same the number of Nitrogens is not. Looking at your calculations, you have 0.446 moles of Oxygen but how much Nitrogen?

[wanabe]

Well there are 3 N to the 6 O in C_7 H_5 (NO_2)_3.... So... 0.466 mol O(3 mol N/6 mol 0)= 1.398 Mol N? Right? Geez I feel dumb. If that's correct, how can I write that in one unit line equation? what is the proper way to relate the two chemicals? mol O in the one to the mol O in the other?

Edited September 20, 2010 by wanabe

[cypress]

The formula is right but check your math, I get 0.233 Moles N.

 

If you need a one line equation, start with your first attempt but don't stop there just add this last equation onto the end of the previous one.

 

You nearly had it right to begin with, really you did most of the work.

[wanabe]

13.4 g C_6H_12 O_6(1mol C_6H_12 O_6/180.15768g C_6H_12 O_6)(6 mol O/1 mol C)(3 mol N/6 mol 0)=0.2231378646 mol N !!!!!!!!!!!!!(not 0.233 but) Thank you cypress! I just needed a little socratic questioning. Ug, just that one last step, how annoying. hahaha 105.3% hw grade for me!