Question

For the vaporization of liquid water at 298 K, ΔS^o = 118.8 J/K mol and ΔH^o = +44.0 kJ/mol. What is ΔS^o_univ (in J/K mol) at this temperature?

Answer 1

Given S^o_sys = 118.8 J/(K.mol)

Temperature, T = 298 K

H^o = 44.0 kJ/mol * (1000 J/1 KJ) = 44000 J/mol

S^o_surr = - H^o / T

=> S^o_surr = - (44000 J/mol) / 298 K

=> S^o_surr = 147.7 J/(K.mol)

S^o_univ = S^o_sys + S^o_surr

=> S^o_univ = 118.8 J/(K.mol) + 147.7 J/(K.mol)  

=> S^o_univ = 266.5 J/(K.mol) (Answer)