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Using the following thermochemical equations, determine the enthalpy of vaporisation of water: H₂(g) + 1/2 O₂(g) → H₂O(l), ΔH = -286 kJ H₂(g) + 1/2 O₂(g) → H₂O(g), ΔH = -245.5 kJ

1. 6.02 kJ
2. 40.5 kJ
3. 62.3 kJ
4. 1.25 kJ

Correct answer: 40.5 kJ

Solution

H2O(l) -> H2O(g): dHvap = (-245.5) - (-286) = 40.5 kJ. The stored 62.3 kJ is wrong.

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