Question

Assuming that water vapour is an ideal gas, the internal energy change ($\Delta U$) when 1 mol of water is vapourised at 1 bar pressure and 100°C, (given : molar enthalpy of vapourisation of water at 1 bar and 373 K = 41 kJ mol⁻¹ and R = 8.3 J mol⁻¹ K⁻¹) will be
(a) 41.00 kJ mol⁻¹
(b) 4.100 kJ mol⁻¹
(c) 3.7904 kJ mol⁻¹
(d) 37.904 kJ mol⁻¹

Answer 1

(c) 3.7904 kJ mol⁻¹ hope that it helps

Answer 2

Question:

Assuming that water vapour is an ideal gas, the internal energy change () when 1 mol of water is vapourised at 1 bar pressure and 100°C, (given : molar enthalpy of vapourisation of water at 1 bar and 373 K = 41 kJ mol⁻¹ and R = 8.3 J mol⁻¹ K⁻¹) will be

(a) 41.00 kJ mol⁻¹

(b) 4.100 kJ mol⁻¹

(c) 3.7904 kJ mol⁻¹

(d) 37.904 kJ mol⁻¹

Solution:

ΔU = ΔH – ΔnRT

= 41000 – 1 × 8.314 × 373

= 41000 – 3101.122

= 37898.878 J mol^–1

= 37.9 kJ mol^–1.

Hence, Option D is correct.