Determine the numbers of calcium are needed to react

Question

1.Calculate the percentage yield for the reaction PCl₃(g) + Cl₂(g) -----> PCl₅(g) if 127.0 g of PCl₅ are produced when 83.4 g of Cl₂ react with excess PCl₃?  

a) 125% b) 51.9%

c) 66.3% d) 31.4% e)43.7%

2. Determine the numbers of calcium are needed to react with the 1.55g of water to make the calcium hydroxide and the hydrogen gas?  

a) 1.72 g    b) 6.90 g

c) 0.862 g  d) 0.696 g

e) 3.44 g