Acetylene Gas May Be Produced by Carefully Adding Water to Calcium

Multiple Choice

Acetylene gas may be produced by carefully adding water to calcium carbide, according to the equation: CaC₂(s) + 2 H₂O(l) → Ca(OH) ₂(s) + C₂H₂(g)
When a 37 g sample of an impure calcium carbide was treated with excess water, 13 g of acetylene gas was produced. If the reaction is essentially 100% efficient, what was the percentage of nonreacting impurity in the carbide sample?

A) 86%
B) 58%
C) 42%
D) 35%
E) 13.5%