Calculate ΔG°rxn for the reaction CaCO3(s)----->CaO(s)+CO2(g)

Question

Calculate ΔG°_rxn for the reaction:

CaCO3(s)----->CaO(s)+CO2(g)

use the following reactions and their given Grxn values.

 

Ca(s)+CO2(g)+1/2O2(g)--->CaCO3(s)  ΔG°rxn =-734.4

Ca(s)+1/2O2(g) -----> CaO(s)  ΔG°rxn = -1206.6

 

Answer 1

Ca(s) + CO2 (g) + 1/2 O2 (g) -----> CaCO3(s), ΔG' = - 734.4 kJ ----(1)

2Ca(s) + O2(g) ------>2CaO(s), G" = - 1206.6 kJ  ---(2)

CaCO3(s) -------> CaO(s) +CO2(g) ; ΔG rxn = x  ---(3)

Eq(3 ) can be obtained from the remaining two Equations as follows

eq(3) = reverse of eq(1) + (1/2) equation (2)

So, ΔG rxn = -(ΔG' ) + (1/2)*ΔG"

                = -(-734.4KJ) + (1/2) * (-1206.6 KJ)

                = +131.1 KJ