Dissociation of water takes place in two steps: H2O → H + OH; Δ H = +497.8 kJ OH → H + O; Δ H = 428.5 kJ What is the bond energy of O — H bond ?

Question

Dissociation of water takes place in two steps: H2O → H + OH; Δ H = +497.8 kJ OH → H + O; Δ H = 428.5 kJ What is the bond energy of O — H bond ? (A) 463.15 kJ mol-1 (B) 428.5 kJ mol-1 (C) 69.3 kJ mol-1 (D) 926.3 kJ mol-1

Tardigrade Admin · Accepted Answer

In given 2 reactions, Δ H is basically representing bond energies of H - O bond. So, our answer should be average of these two Δ H values. Hence, Average of two bond dissociation energies: (497.8+428.5/2)=463.15 kJ mol -1

Q. Dissociation of water takes place in two steps :
$H_{2} O \to H + O H$ ; $Δ H = + 497.8 k J$
$O H \to H + O$ ; $Δ H = 428.5 k J$
What is the bond energy of $O — H$ bond ?

$463.15 k J m o l^{- 1}$

$428.5 k J m o l^{- 1}$

$69.3 k J m o l^{- 1}$

$926.3 k J m o l^{- 1}$

In given 2 reactions, $Δ H$ is basically representing bond energies of $H - O$ bond. So, our answer should be average of these two $Δ H$ values.
Hence, Average of two bond dissociation energies: $\frac{497.8 + 428.5}{2} = 463.15 k J m o l^{- 1}$

Q. Dissociation of water takes place in two steps : H2​O→H+OH; ΔH=+497.8kJ OH→H+O; ΔH=428.5kJ What is the bond energy of O—H bond ?

463.15kJmol−1

428.5kJmol−1

69.3kJmol−1

926.3kJmol−1