Answer:
-1268 kJ
Step-by-step explanation:
The molar enthalpy of combustion of C6H6 is -3170 kJ/mol
2C6H6(g) + 15O2(g) → 12CO2(g) + 6H2O(g)
Therefore;
when 1 mole of C6H6 undergoes combustion, an energy of -3170 kJ/mol is released.
Therefore; for 0.40 mole
= 0.4 × -3170 kJ
= -1268 kJ