Determine the mass of water to be added to the quicklime (CaO) to obtain 1 kg of hydrated lime [Ca (OH) 2].

| January 6, 2021 | education

Determine the mass of water to be added to the quicklime (CaO) to obtain 1 kg of hydrated lime [Ca (OH) 2]. Make a reaction equation. How much quicklime (g, mol) reacted?

1.Calculate the amount of calcium hydroxide substance (slaked lime) according to the formula:
n = m: M, where M is molar mass.
M (Ca (OH) 2) = 40 + 2 × (16 + 1) = 40 + 34 = 74 kg / kmol.
n = 1 kg: 74 kg / kmol = 0.01 kmol = 10 mol.
2. Let’s compose the reaction equation:
CaO + H2O = Ca (OH) 2.
According to the reaction equation, 1 kmol of calcium hydroxide accounts for 1 kmol of water, that is, the substances are in quantitative ratios of 1: 1, which means their amount of substances will be the same.
n (H2O) = n (Ca (OH) 2) = 10 mol.
Let’s calculate the mass of water by the formula: m = n M,
M (H2O) = 18 g / mol.
m = 18 g / mol × 10 mol = 180 g.
Let’s find how much quicklime (CaO) has reacted.
According to the reaction equation, 1 kmol of calcium hydroxide accounts for 1 kmol of calcium oxide, that is, the substances are in quantitative ratios of 1: 1, which means their amount of substances will be the same.
n (CaO) = n (Ca (OH) 2) = 10 mol.
Let’s find the mass of calcium oxide by the formula:
m = n M.
M (CaO) = 40 + 16 = 56 g / mol.
m = 10 × 56 g / mol = 560 g / mol.
Answer: m (CaO) = 560 g / mol; m (H2O) = 180 g.



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