475 grams of solid calcium oxide reacts with water vapor to form solid calcium hydroxide. Calculate the heat of reaction. (A) - 221.1 kcal
(B) + 290.8 kcal
C) - 290.8 kcal
(D) + 324.6 kcal
(E) + 221.1 kcal

(A) - 221.1 kcal

Explanation:

Based in the reaction:

CaO(s) + H₂O(g) → Ca(OH)₂ ΔH = -109kJ/mol

When 1 mole of CaO reacts per mole of water vapor producing calcium hydroxide there are released -109kJ

475g of CaO (Molar mass CaO: 56.08g/mol) are:

475g CaO × (1mol / 56.08g) = 8.47 moles of CaO

As 1 mole of CaO in reaction release -109kJ, 8.47 moles release:

8.47 mol CaO × (-109 kJ / 1 mol CaO) = -923.2kJ are released

As 1 kCal = 4.184kJ:

-923.2kJ × (1kCal / 4.184kJ) =

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