Consider the following data Heat of combustion of H 2 ( g ) = – 241 . 8 kJ mol – 1 Heat of combustion of C ( s ) = – 393 . 5 kJ mol – 1 Heat of combustion of C 2 H 5 OH ( l ) = – 1234 . 7 kJ mol – 1 The heat of formation of C 2 H 5 OH ( l ) is ( – ) _____ kJ mol – 1 (Nearest integer).

Step-by-step solution

C 2 H 5 OH l → 2 CO 2 g + 3 H 2 O l + + 3 O 2 g Heat of combustion = Heat of formation of products - Heat of formation of reactants Heat of combustion of hydrogen is equal to heat formation of water, and heat of combustion of carbon is equal to heat of formation of carbon dioxide. ∆ H C = 2 ∆ H f o CO 2 + 3 ∆ H f o H 2 O - ∆ H f o C 2 H 5 OH l – 1234 . 7 = [ 2 × ( – 393 . 5 ) + 3 × ( – 241 . 8 ) ] - ∆ H f o C 2 H 5 OH l ∆ H f o C 2 H 5 OH = - 277