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Applying Hess’s law, equation (i) can be obtained by adding equations (ii) and (iii). x = y + z. ΔvapH = 40.66 kJ mol⁻¹. T = 100 + 273 = 373 K. ΔE = ?

1. (a) ΔE = ΔvapH − RT
2. (b) ΔE = ΔvapH + RT
3. (c) ΔE = ΔvapH × RT
4. (d) ΔE = ΔvapH / RT

Correct answer: (a) ΔE = ΔvapH − RT

Solution

Using the relation ΔE = ΔH − ΔnRT, for vaporization (liquid to gas), Δn = 1. Thus, ΔE = ΔvapH − RT.

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