Consider the following reaction: 4NH3 + 7O2 (arrow) 4NO2 + 6H2O.

Question

A) How many moles of NH3 react with 5.64 mol of O2?
B)How many moles of NO2 are obtained from 3.27 mol of O2?
C) How many moles H2O will be produced from 8.95 g of NH3?
D)How many grams of NH3 will be needed to produce 0.0160 g NO2?

Please show work and explain how you got them!! I am lost and I have 10 problems like this!!

Answer 1

Two rules to follow in chemistry problems.
1. Work in mols. You get mols two ways. The first is when you have grams; that's mols = grams/molar mass. The second is when you have a solution; then mols = M x L.
2. When you have mols you can convert mols of anything in the equation to mols of anything else in the equation by using the coefficients in the balanced equation.

a. 5.84 mols O2 x (4 mols NH3/7 mols O2) = 5.84 x 4/7 = ?

b. same procedure as in a. Note that the factor you use (in the above case 4/7) cancels the mols O2 unit and converts to mols NH3 unit. In these conversions the unit you don't want to keep always goes in the denominator of the fraction and the unit you want to convert to goes in the numerator of the fraction.

c. When you have grams, first convert to mols.
mols NH3 = grams/molar mass = 8.95/17 \ estimated 0.53. Then convert to mols of what you want.
0.53 mols NH3 x (6 mols H2O/4 mol NH3) = 0.53 x (3/2) = estimated 0.79 mols H2O. The problem doesn't ask you to convert to grams (but the next one does). To find grams just g = mols x molar mass = about 0.79 x 18 = ?