When 4.0 mol H2 reacts with excess O2, 3.0 mol H2O are actually produced, what is the percent yield of the reaction?

2H2 + O2 - -->2H2O

A. 25%

B. 50%

C. 75%

D. 100%

2H2 + O2 - -->2H2O

from equation 2 mol 2 mol

given 4 mol 3 mol

How much

we could get

using 4 mol of H2. 4 mol x mol

2 mol H2 gives 2 mol H2O, 4 mol H2 could give 4 mol H2O.

So, 4 mol H2O is theoretical yield.

% yield = (actual yield/theoretical yield) * 100% = (3 mol/4 mol) * 100% = 75 %

Answer is C. 75%.