Delta Fares

Calculate (delta) Grnx for the following reaction?

CaCO3(s) -->CaO(s) + CO2(g) Use the following reactions and given (delta) Grnx values: Ca(s) +CO2(g) +1/2O2(g) -->CaCO3 (delta) Grnx =-734.4 kJ 2Ca(s) +O2(g) -->2CaO(s) (delta) Grnx=-1206.6 kJ Express your answer using four significant figures.

Public Comments

1. CaCO3(s) --> Ca(s) +CO2(g) +1/2O2(g) ΔGrxn = +734.4 kJ Ca(s) +(1/2)O2(g) --> CaO(s) ΔGrxn= -1206.6 / 2 kJ Notice what I did with the two standard reactions you gave me -- something similar to Hess' Law with enthalpies of formation. I divided the 2nd reaction by 2, which means ΔGrxn is halved as well. I flipped the first reaction, so the ΔGrxn sign changes from + to -. Now, if you add up the two reaction equations, you'll notice you'll get the same reaction as the question. Further adding of the ΔGrxn values will get you your desired value. ♠