Calculate the amount of heat evolved during the complete combustion of 100 ml of liquid benzene from the following data. Predict your answer as 
(in KJ/mole).
(i)18 g of graphite on complete combustion evolve 585 KJ heat
(ii)15540 KJ heat is required to dissociate all the molecules of 1 litre water into H 2 and O 2 .
(iii)The heat of formation of liquid benzene is 48 kJ/mol
(iv)Density of C 6 H 6 ( λ ) = 0.87 g/m λ
Predict your answer as 
(in KJ/mole).
Text Solution
Verified by ExpertsCHECK THE SOLUTION.
(36 kJ )
(i) C(s) + O 2 (g) ⎯→ CO 2 (g) ; 
= – 390 KJ/mol ; 
= 
× 12
(ii) H 2 (g) + 
O 2 (g) ⎯→ H 2 O ( λ ) ; 
= – 280 KJ/mol ; 
= 
(iii) C 6 H 6 ( λ ) + 
O 2 (g) ⎯→ 6CO 2 (g) + 3H 2 O ( λ ) ; 
= –48
∴ Δ Hº = [6(–390) + 3 (–280)] – 48= –3228 KJ/ mol
Mass of benzene is = 0.87 × 100 = 87 g
∴ Heat evolved from 87 g benzene = 3600 KJ.
Hence, 
= 36 kJ.
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