Consider the chemical equation.

Question

2H2 + O2 -> 2H2O

What is the percent yield of H2O if 87.0 g of H2O is produced by combining 95.0 g of O2 and 11.0 g of H2?
a 56.5%
b 59.0%
c 88.5%
d 99.7%

Answer 1

This is a limiting reagent (LR) problem and a percent yield rolled into one. You know it is a LR problem because amounts are given for BOTH reactants.
mols H2 = grams/molar mass = ?
mols O2 = grams/molar mass = ?

Using the coefficients in the balanced equation, convert mols H2 to mols H2O.
Do the same and convert mols O2 to mols H2O.
It is likely that these two values for mols H2O will not agree; the correct value in LR problems is ALWAYS the smaller value and the reagent responsible for that is called the LR.
Take the smaller number and convert it to grams H2O. g H2O = mols H2O x molar mass H2O = ? This the theoretical yield (TY).
The problem gives you the actual yield (AY) of 87.0 g.
%yield = [AY/TY]*100 = ?

Answer 2

88.5