# What mass of calcium reacts with water if 7.4 grams of calcium hydroxide is formed as a result of the reaction?

January 13, 2021 | education

| 1.Calculate the amount of calcium hydroxide substance by the formula:

n = m: M, where M is molar mass.

M (Ca (OH) 2) = 40 + 2 × (16 + 1) = 40 + 34 = 74 g / mol.

n = 7.4: 74 g / mol = 0.1 mol.

2. Let’s compose the reaction equation:

Ca + 2H2O = Ca (OH) 2 + H2.

According to the reaction equation, there is 1 mole of calcium per 1 mole of calcium hydroxide, that is, the substances are in quantitative ratios of 1: 1, which means their amount of substance will be the same.

n (Ca) = n (Ca (OH) 2) = 0.1 mol.

3.Calculate the mass of calcium by the formula: m = n M,

M (Ca) = 40 g / mol.

m = 40 g / mol × 0.1 mol = 4 g.

Answer: m = 4 g.

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