Question

How many moles of CaO are required to react with an excess of water to form $370$ grams of calcium hydroxide?

• A. $1.0$
• B. $2.0$
• C. $3.0$
• D. $4.0$
• E. $5.0$

Answer 1

Answer: (E)

$5.0$

$CaO+H_{2}O\to Ca(OH{)}_2$
One mole of CaO will give one mole of calcium hydroxide.
The molar mass of calcium hydroxide is $40.1+2(16+1)=74.1g/mol$.
370 grams of calcium hydroxide corresponds to $\frac{370g}{74.1g/mol}=5.0$ moles.
Hence, 5.0 moles of CaO are required to react with an excess of water to form 370 grams of calcium hydroxide.