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The total energy needed to break all three P−H bonds in PH3(g) is 954 kJ mol⁻¹. What is the energy required to break a single P−H bond?

1. 318 kJ mol⁻¹
2. 1272 kJ mol⁻¹
3. 213 kJ mol⁻¹
4. None of these

Correct answer: 318 kJ mol⁻¹

Solution

PH3 has three equivalent P-H bonds, so the average bond enthalpy is 954/3 = 318 kJ/mol. The correct option is index 0 (318 kJ/mol); the stored choice 213 is wrong.

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