Homework Help: Chemistry

Posted by Sarene on Tuesday, September 28, 2010 at 12:10pm.

Could someone please check my answers/work for the following questions.
EQUATION: 3H2+N2 -->2NH3

1) How many grams of NH3 can be produced from 3.98 mol of N2?
3.98 mol N2(2 mol NH3/2 mol H2)=2.65 mol
Convert to grams: 2.65(17.0)=45.14g

2.)How many grams of H2 are needed to produce 10.41g of NH3?
10.41g/17.0=0.61 mol
0.61 mol NH3(3mol H2/1mol N2)= 1.83 mol
(1.83)(2.016)=3.75g

3.)How many molecules of NH3 are produced from 4.98x10^-4g of H2?
(4.98X10^-4g/2.016)=2.47X10^-4mol
2.47x10^-4mol H2x (2mol NH3/1mol N2)=4.94 X10^-4 mol NH3(6.02X10^23)= 2.97 X 10^20 molecules.

Please let me know if I've done these questions correctly. Thanks

Chemistry - DrBob222, Tuesday, September 28, 2010 at 1:45pm
All are incorrect for the same reason. Everything is ok except the conversion factors.

1) How many grams of NH3 can be produced from 3.98 mol of N2?
3.98 mol N2(2 mol NH3/2 mol H2)=2.65 mol
Convert to grams: 2.65(17.0)=45.14g

3.98 mol N2 x (2 mol NH3/1 mol N2) = 7.96 mol NH3.
Then 7.96 mol NH3 x (17.0 g NH3/mol)= ?? g NH3.

Note the mole N2 cancel in my work to leave mol NH3 as the unit to keep. In your work, mol NH3 is the unit you keep (correct) BUT mol N2 in the numerator does not cancel with the mol H2 in the denominator. The other problems you did also have the same error. Otherwise your work is VERY good. My guess, since all were done the same way, is that you had a problem with your thought process. Just remember the factor used must cancel the unit you have and convert to the unit you want to keep.
Chemistry - Anonymous, Saturday, February 25, 2012 at 3:39pm
H2(g)+ N2(g)NH3(g)
Chemistry - Anonymous, Saturday, February 25, 2012 at 3:39pm
H2(g)+ N2(g)NH3(g) Please balance equation. Thanks

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