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) =

-220.7kCal ≈ (A) - 221.1 kcal