The standard molar heats of formation of ethane, carbon dioxide, and liquid water ate `-21.1, -94.1`, and `-68.3kcal`, respectively. Calculate the standard molar heat of combustion of ethane.

The standard molar heats of formation of ethane, carbon dioxide, and l

1.	The standard molar heats of formation of ethane, carbon dioxide, and liquid water ate `-21.1, -94.1`, and `-68.3kcal`, respectively. Calculate the standard molar heat of combustion of ethane.
Answer» The required chemicla equation for combustion of ethane is `2C_(2)H_(6)(g) +7O_(2)(g) = 4CO_(2)(g) +6H_(2)O(l), DeltaH^(Theta) = ?` The equation involves `2mol` of `C_(2)H_(6)`, heta of combustion of thene will be `=(DeltaH^(Theta))/(2)` `DeltaH^(Theta) = Delta_(f)H^(Theta) ("products") - Delta_(f)H^(Theta) ("reactants")` `[4 xx Delta_(f)H_((CO_(2)))^(Theta)+ 6Delta_(f)H_((H_(2)O))^(Theta)]` `-[2Delta_(f)H_((C_(2)H_(6)))^(Theta) + 7Delta_(f)H_((O_(2)))^(Theta)]` `= [4 xx (-94.1) + 6 xx (-68.3)] -[2xx (-2.11) +7 xx 0]` `=- 376.4 - 409.8 + 42.2` `= 744.0 kcal` `(DeltaH^(Theta))/(2)=` Heat of combustion of ethane ` = (744.0)/(2) = - 372.0 kcal`

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The standard molar heats of formation of ethane, carbon dioxide, and liquid water ate `-21.1, -94.1`, and `-68.3kcal`, respectively. Calculate the standard molar heat of combustion of ethane.

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