If a student starts with 615g of Co(NO3)2 and obtains a 57.3% yield of CoS, what mass of CoS is isolated?
Co(NO3)2 + K2S ---> CoS + 2KNO
Here is a worked example of a stoichiometry problem. Just follow the steps. At the end, the grams you obtain will be the theoretical yield. Then
%yield = (actual yield/theoretical yield)*100, substitute and solve for actual yield.
http://www.jiskha.com/science/chemistry/stoichiometry.html