This problem demands a fairly deep understanding of thermodynamic relationships.
The universe in this problem is but the system and the surroundings.
#CaO(s) + H_2O(l) rightleftharpoons Ca(OH)_2(s)#
Consider,
#DeltaS_("univ") = DeltaS_("sys") + DeltaS_("surr")#,
The change in enthalpy or entropy of a system is the sum of the property for products less the sum of the property for reactants,
#DeltaS = (DeltaH)/T#, and,
#-DeltaH_("sys") = DeltaH_("surr")#
#=> -(DeltaH_("sys"))/T = (DeltaH_("surr"))/T#
#=> DeltaS_("surr") = -(DeltaH_("sys"))/T#
Hence,
#DeltaH_("sys") = -65.2kJ#
#therefore DeltaH_("surr") = 65.2kJ#, and #DeltaS_"surr" = (6.52*10^4J)/(298K) approx (218.7J)/K#
Moreover,
#DeltaS_"sys" = (-26.4J)/K#
#DeltaS_("univ") = DeltaS_"surr" + DeltaS_"sys" approx (192.3J)/K#
I'm open to feedback if I made a mistake!
