Home Chemistry Thermodynamics and Thermochemistry Bond Energy Given that 2H 2 (g) + O 2 (g) ⎯ ⎯ → → H 2 O(…
Chemistry Thermodynamics and Thermochemistry Bond Energy Single Correct MCQ
Published on: August 14, 2026

Given that 2H 2 (g) + O 2 (g) ⎯ ⎯ → → H 2 O(g) , Δ Δ H = –115.4 kcal the bond energy of H–H and O = O bond respectively is 104 kcal and 119 kcal, then the O–H bond energy in water vapour is

A
110.6 kcal / mol
B
–110.6 kcal
C
105 kcal / mol
D
None

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Text Solution

Verified by Experts
The correct answer is:
A

We know that heat of reaction

Δ Δ H = Σ Σ B.E. (reactant ) – Σ Σ B.E (product)

For the reaction,

2H–H(g) + O = O (g) ⎯ ⎯ → → 2H – O–H(g)

Δ Δ H = –115.4 kcal, B.E. of H–H = 104 kcal

B.E. of O=O = 119 kcal

Since one H 2 O molecule contains two O–H bonds

–115.4 = (2 × × 104) + 119 – 4 (O–H) bond energy

∴ ∴ 4 (O–H) bond energy = ( 2 × × 104) +119+115.4

i.e., O–H bond energy =

= 110.6 kcal mol –1

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