Answer:
The answer to your question is:
% yield = 84.8
Explanation:
Data
MW CaO = 56 g
MW H2O = 18 g
MW Ca(OH)2 = 74 g
CaO = 2.5 g
Ca(OH)2 = 2.8 g
Balanced Reaction
          CaO  +   H2O    ⇒    Ca(OH)2
          56g of CaO   --------------- 74 g  Ca(OH)2
          2.5 g         ---------------  x
          x = 3.3 g of Ca(OH)2
% yield = [tex]\frac{2.8}{3.3} x 100[/tex]
% yield = 84.8