Methanol (CH4O) is converted to bromomethane (CH3Br) as follows:

Question

CH4O + HBr --> CH3Br + H2O

If 12.23 g of bromomethane are produced when 5.00 g of methanol is reacted with excess HBr, what is the percent yield?

Answer 1

Here is a worked example of how to solve simple stoichiometry problems, including percent yield.
http://www.jiskha.com/science/chemistry/stoichiometry.html