Answer:
ΔH = -111.1kJ
Explanation:
ΔH of any reaction could be obtained from similar reaction doing algebraic operations. Using the reactions:
(1) CaO(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l) ΔH = -186 kJ
(2) CaO(s) + H₂O(l) → Ca(OH)₂(s) ΔH = -62.3 kJ
(3) Ca(OH)₂(s) → Ca(OH)₂(aq) ΔH = - 12.6 kJ
(1) - (2):
Ca(OH)₂(s) + 2HCl(aq) → CaCl₂(aq) + 2H₂O(l)
ΔH = -186kJ - (-62.3kJ) = -123.7kJ
This reaction -(3):
Ca(OH)₂(aq) + 2HCl(aq) → CaCl₂(aq) + 2H₂O(l)
ΔH = -123.7kJ - (-12.6kJ) = -111.1kJ