Answer:
(A) - 221.1 kcal
Step-by-step 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