(1) For the given heat of reaction,i)  C(s)+O2(g)=CO2(g)+97kcal ii)  CO2(g)+C(s)=2CO(g)−39kcalthe heat of combustion of CO(g) is:

Subtracting equation (ii) from equation (i), we getC(s)+O2(g)=CO2(g)+97kcalCO2(g)+C(s)=2CO(g)−39kcal--------------------------------------------------- or −CO2(g)+O2(g)=CO2(g)−2CO(g)+136kcal or 2CO(g)+O2=2CO2(g)+136kcal or, CO(g)+12O2(g)=CO2(g)+68kcalRequired value : 68 kcal.