physical chemistry CaO(s) is a desiccant. The balanced chemical equation for the

Question

physical chemistry

CaO(s) is a desiccant. The balanced chemical equation for the reaction of CaO water vapor is CaO(3) + H_2O(g) rightarrow Ca(OH)_2(g) Thermochemical data for the reactants and products in the above equation are given below (for T = 25 degree C) a) What are Delta G degree_run Delta H degree _run Delta S degree_rms, and K_eq for reaction 3.1 M T = 25. degree C? b) What are Delta G degree _run and K_pq for reaction 3.1 at T = 100 degree C, assuming the values for Delta H degree_run and Delta S degree run are independent of temperature? c) What are Delta G degree_run and K_eq for reaction 3.1 at T = 100 degree C. when the temperature dependence of Delta H degree_run and Delta S degree_run are correctly accounted for?

Explanation / Answer

For the reaction, CaO+ H2O--->Ca(OH)2

standard change in enthalpy   = 1* standard enthalpy of Ca(OH)2- { 1* standard enthalpy of CaO+ 1* standard enthalpy of H2O}

1, 1 and 1 are stoichiometric coeficients of Ca(OH)2, CaO and H2O.

Standard enthalpy change, deltaH0=-986.1- {-635.1-241.8)=-109.2 Kj

On similar grounds, standard entropy change, deltaS0= 83.39- (38.21+188.23) =-143.05 J/K

Standard gibbs free energy change, deltaG0= -898.4- {-603.5-228.6)=-66.3 Kj

At 100 deg.c (100+273= 373K), deltaG= deltaH- TdeltaS= -109.2*1000+373*143.05 =-55842.4 J

deltaG= -RTlnK, lnK= 55842.4/(8.314*373)= 6.613*107

Accounting for temperature change, deltaH= deltaH0+DeltaCp*(T2-T1)=-109.2+(87.49-{42.12+33.58)}*(100-25)= -108.3 Kj

deltaS= deltaSO+deltaCP/R = -143.05+11.79/8.314 =-141.6 J/K

deltaG = deltaH- TdeltaS=-108.3*1000+373*141.6/1000=-55483.2 Joules

lnK= -deltaG/RT= 55483.2/(8.314*373), K= 5.9*107

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