Q.

Combustion of 1 mole of benzene is expressed at C6H6(l)+152O2(g)6CO2(g)+3H2O(l)

The standard enthalpy of combustion of 2 mol of benzene is – 'x' kJ. x = ____________ .           

Given:

1.  Standard Enthalpy of formation of 1 mol of C6H6(l), for the reaction 6 C (graphite) +3H2(g)C6H6(l) is 48.5 kJ mol-1.

2.  Standard Enthalpy of formation of 1 mol of CO2(g), for the reaction C(graphite) +O2(g)CO2(g) is –393.5 kJ mol-1.

3.  Standard Enthalpy of formation of 1 mol of H2O(l), for the reaction

     H2(g)+12O2(g)H2O(l) is -286kJ mol-1.                  [2024]


Ans.

(6535)

C6H6(l)+152O2(g)6CO2(g)+3H2O(l)

ΔHr=ΔfH(products)-ΔfH(reactants)

ΔHr=6ΔfH(CO2)+3ΔfH(H2O)-ΔfH(C6H6)+152ΔfH(O2)

         =[6×(-393.5)+3(-286)-48.5+152×0]kJ mol-1

         =-3267.5kJ mol-1

ΔHr(2mol)=2×-3267.5kJ mol-1=6535kJ mol-1