Question

The enthalpy of combustion of C6H6.is - 3250 kJ when 0.39g of C6H6 is burnt in excess of oxgyen in an
open vessel, the amount of heat envolved is:
(1) 8.32 kJ
(2) 12.36 kJ
(3) 16.25 kJ
(4) 20.74 kJ​

Answer 1

Answer:

0.39 g of C₆H₆ liberate heat = - 16.25 kJ

Explanation:

Given

enthalpy of combustion of C₆H₆  = 3250 kJ

mass of C₆H₆ = 0.39 g

amount of heat = ??

Solution

The enthalpy of combustion of C₆H₆ is - 3250 kJ

this means

78 g of C₆H₆ liberate heat = - 3250 kJ

1 g of C₆H₆ liberate heat = - 3250 kJ / 78

0.39 g of C₆H₆ liberate heat = (- 3250 X 0.39)/ 78

By solving we get

0.39 g of C₆H₆ liberate heat = - 16.25 kJ

Answer 2

Answer:

Combustion of benzene can be represented as follows C6H6+O2→6CO2+H2O+3250 KJ 78 g of C6H6 produce 3250 kJ heat 1 g will produce 325078kJ heat 39 g will produce =325078×0.39kJ NOTE: Enthalpy of combustion is the amount of heat liberated when one mole of a substance is burnt in excess of air.