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

CaO + H20 - - > Ca (OH) 2

Calcium Hydroxide has a relative molecular mass of approximately 74 grams. Therefore, with 370 grams provided, we have 370g/74g, or 5 moles.

Therefore, due to molar ratios, 5 moles of CaO must have reacted with 5 moles of H2O to form 5 moles of Ca (OH) 2.

The answer to your question is 5 moles of CaO or 280 g of CaO