How do I calculate ΔHrxfollowing reaction? CaO(s)+CO2(g)→CaCO3(s) Use the following reactions and given ΔH values: Ca(s)+CO2(g)+1/2O2(g)→CaCO3(s), ΔH= -812.8 kJ 2Ca(s)+O2(g)→2CaO(s), ΔH= -1269.8 kJ Express your answer using four significant figures.
We are to calculate the heat of following reaction.
Reversing the equation  and dividing both sides by
Now adding  and  we can get desired heat of raction