Calculate the heat of hydrogenation of C2H2 to C2H4 H2(g)+12O2(g)⇌H2O(l);ΔH=−68.32kcal C2H2(g)+12O2(g)⇌2CO2(g)+H2O(l);ΔH=−310.61kcal C2H4(g)+32O2(g)⇌2CO2(g)+2H2O(l);ΔH=−337.32kcal
A
-51.46 kcal
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B
-41.46 kcal
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C
81.46 kcal
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D
41.46 cal
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Solution
The correct option is B -41.46 kcal Given, H2(g)+12O2(g)⇌H2O(l);ΔfH=−68.32kcal C2H2(g)+12O2(g)⇌2CO2(g)+H2O(l);ΔcombH=−310.61kcal C2H4(g)+32O2(g)⇌2CO2(g)+H2O(l);ΔcombH=−337.32kcal
Heat of hydrogenation=heat of formation of water +heat of combustion of C2H2 - heat of combustion of C2H4
Heat of hydrogenation=ΔfH(H2O)+ΔcombH(C2H2(g))-ΔcombH(C2H4(g))
Heat of hydrogenation=(-68.32 - 310.61 + 337.32) kcal
Heat of hydrogenation= −41.61kcal