Question

Calculate the heat of hydrogenation,
$C_2{H}_4\left(g\right)+H_2\left(g\right)⟶C_2{H}_6\left(g\right)$
given that, the heats of combustion of ethylene, hydrogen and ethane are $-337.0,-68.4$ and $-373.0$ $kcal$ respectively.

• A. $-32.4kcal$
• B. $32.4kcal$
• C. $22.4kcal$
• D. $-22.4kcal$

Answer 1

The correct option is A $-32.4kcal$

Heat of hydrogenation = heat of combustion of ethylene + heat of combustion of hydrogen - heat of combustion of ethane

Heat of hydrogenation = $-337+(-68.4)-(-373)$ = $-32.4kcal$