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.

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Answer 1 · 2017-01-31T09:13:21

Given
#Ca(s)+CO_2(g)+1/2O_2(g)→CaCO_3(s), ΔH_1= -812.8 kJcolor(red)(... [1])#
#2Ca(s)+O_2(g)→2CaO(s), ΔH_2= -1269.8 kJcolor(red)(...[2])#

We are to calculate the heat of following reaction.

#CaO+CO_2->CaCO_3,DeltaH_"rx"#

Reversing the equation [2] and dividing both sides by #2# we get
#CaO->Ca+1/2O_2,DeltaH_3=634.9kJcolor(red)(...[3])#

Now adding [1] and [3] we can get desired heat of raction

#color(blue)(CaO+CO_2->CaCO_3,DeltaH_"rx"=DeltaH_1+DeltaH_3)#

#=>DeltaH_"rx"=(-812.8+634.9)kJ#

#=>color(red)(DeltaH_"rx"=-177.9kJ)#