The standard ethelpy of combustion at `25^(@)C` of hydrogen, cyclohexene `(C_(6)H_(10))`, and cyclohexane `(C_(6)H_(12))` are `-241,-3800`, and `-3920 kJ mol^(-1)` repectively. Calculate the heat of hydrogenation of cyclohexane.

Answer

`-121kJ" " mol^(-1)`

Explanation

`H_(2)(g)+(1)/(2)O_(2)(g)toH_(2)O(g)," "(DeltaH=-241kj" "mol^(-1))` . . (i)
`C_(6)H_(10)(g)+(17)/(2)O_(2)(g)to6CO_(2)(g)+5H_(2)O(g),(DeltaH=-3800kJ" "mol^(-1))` . . .(ii)
`C_(6)H_(12)9g)+9O_(2)(g)to6CO_(2)(g)+6H_(2)O,(DeltaH=-3920kJ" "mol^(-1))` . . (iii)
Adding eqs. (i) and (ii) and subtracting eq. (iii),
`C_(6)H_(10)(s)+H_(2)(g)toC_(6)H_(12)(s),`
`DeltaH=-241-3800-(-3920)=-121kJ" "mol^(-1)`