Question

Given the equation Ca + H2O --> Ca(OH)2 + H2 how many grams of calcium will react completely with 10.0 grams of water? *

Answer 1

Answer: 11.0 g of calcium will react with 10.0 grams of water.

Explanation:

To calculate the moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text {Molar mass}}$

moles of $H_2O$

$\text{Number of moles}=\frac{10.0g}{18g/mol}=0.55moles$

The balanced chemical equation is:

$Ca+2H_2O\rightarrow Ca(OH)_2+H_2$

According to stoichiometry :

2 moles of $H_2O$ require = 1 mole of $Ca$

Thus 0.55 moles of $H_2O$ require=$\frac{1}{2}\times 0.55=0.275moles$  of $Ca$  

Mass of $Ca=moles\times {\text {Molar mass}}=0.275moles\times 40g/mol=11g$

Thus 11.0 g of calcium will react with 10.0 grams of water.