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

`-1121 kJ

Explanation

In this case the required reaction is
`C_(6)H_(10) + H_(2) rarr C_(6)H_(12) , Delta H_(f) = ?`
From the given data, we can write following equations
(i) `H_(2) + (1)/(2) O_(2) rarr H_(2)O, Delta H = - 241 kJ`
(ii) `C_(6) H_(10) + (17)/(2) O_(2) rarr 6 CO_(2) + 5H_(2), Delta H = -3800 kJ`
(iii) `C_( 6) H_(12) 9 O_(2) rarr 6 CO_(2) + 6 H_(2)O , Delta H = -390 kJ`
To get the desired equation add (i) adn (ii) and substract (iii). then
`Delta H = -241 + (-3800) - (-3920) = -121 kJ//"mole"`