One mole of water vaporises reversibly at 373 K and 1 atm; Delta_vapH=40.7 kJ mol^-1 and R=8.314 J mol^-1K^-1 (steam ideal, liquid volume neglected). Select the correct statement(s).

Delta S_sysapprox+109.1 J K^-1.

Delta S_surrapprox-109.1 J K^-1.

Delta S_sysapprox+109.1 J K^-1.

Delta S_surrapprox-109.1 J K^-1.

Delta S_univapprox+109.1 J K^-1.

JEE Advanced levelOne or more correct optionsDifficulty 3 of 3td165

One mole of water vaporises reversibly at $373 K$ and $1 atm$ ; $Δ_{v a p} H = 40.7 kJ mo l^{- 1}$ and $R = 8.314 J mo l^{- 1} K^{- 1}$ (steam ideal, liquid volume neglected). Select the correct statement(s).

At the boiling point

Δ S_{sys} = Δ H / T = 40700/373 = 109.1 J K^{- 1}

. The surroundings supply the heat at the same temperature, so

Δ S_{s u rr} = - 109.1

and

Δ S_{u ni v} = 0

for a reversible process (statement 3 false).

Δ U = Δ H - RT = 40.7 - 8.314 \times 373/1000 = 37.6 kJ

(true).