Question

When 11.0 g of calcium metal is reacted with water, 5.00 g of calcium hydroxide is produced. Using the following balanced equation, calculate the percent yield for the reaction?
Ca(s) + 2 H2O(l) → Ca(OH)2(aq) + H2(g)
84.0%
12.3%
45.5%
24.6%

Answer 1

Here is a worked example of a stoichiometry problem including how to calculate percent yield.
http://www.jiskha.com/science/chemistry/stoichiometry.html

Answer 2

24.6