finding the actual yield using grams and moles

Question

The actual yield for Hg is 618 grams and 1.54 mol oxygen. If 3.55 mol of HgO decompose, calculate the percent yield for oxygen.

 

 

2HgO  to  2Hg +  O₂

Answer 1

First calculate the theoretical yield of O₂: based on the chemical equation, for every 2 mol of HgO you start out with, the yield will be 1 mol O₂. So if you start with 3.55 mols HgO it will yield half as many moles = 1.775 mols O₂. That is your theoretical yield in mols.

 

The actual yield is 1.54 mol. To get the percent yield you divide the actual by the theoretical yield, so 1.54 mol/1.775 mol = 0.8676 (X 100) =86.8% (3 significant figures, since each of the input numbers had 3 sig figs).