Lime is a term that includes calcium oxide (cao, also called quicklime) and calcium hydroxide (ca (oh) 2 also called slaked lime). it is used in the steel industry to remove acidic impurities, in air-pollution control to remove acidic oxides such as so2, and in water treatment. slaked lime is produced by treating quicklime with water: cao (s) + h2o (l) → ca (oh) 2 (s) δh o = - 65.2 kj/mol given the standard enthalpies of formation of cao and h2o are - 635.6 kj/mol and - 285.8 kj/mol, respectively, calculate the standard enthalpy of formation of ca (oh) 2.

Question

Chemistry

Amanda Bowen

2 June, 09:39

Lime is a term that includes calcium oxide (cao, also called quicklime) and calcium hydroxide (ca (oh) 2 also called slaked lime). it is used in the steel industry to remove acidic impurities, in air-pollution control to remove acidic oxides such as so2, and in water treatment. slaked lime is produced by treating quicklime with water: cao (s) + h2o (l) → ca (oh) 2 (s) δh o = - 65.2 kj/mol given the standard enthalpies of formation of cao and h2o are - 635.6 kj/mol and - 285.8 kj/mol, respectively, calculate the standard enthalpy of formation of ca (oh) 2.

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Answers (1)

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Hayden Stephens · Answer 1

Answer: - 986.6 kj/mol

Explanation:

1) Equation given:

CaO (s) + H₂O (l) → Ca (OH) ₂ (s) δh⁰ = - 65.2 kj/mol

2) Standard enthalpies of formation given:

CaO, δhf⁰ = - 635.6 kj/mol

H₂O, δhf⁰ = - 285.8 kj/mol

3) Calculate the standard enthalpy of formation of Ca (OH) ₂.

δh⁰ = ∑δh⁰f of products - ∑ δh⁰f of reactants

Using the mole coefficients of the balanced chemical equation:

δh⁰ = δh⁰f Ca (OH) ₂ - δh⁰f CaO - δh⁰f H₂O

⇒ δh⁰f Ca (OH) ₂ = δh⁰ + δh⁰f CaO + δh⁰f H₂O

⇒ δh⁰f Ca (OH) ₂ = - 65.2 kj/mol - 635.6 kj/mol) - 285.8 kj/mol) = - 986.6 kj/mol.