Question

The heat of combustion of liquid hexane (C6H14) to carbon dioxide and liquid water at 298 K is -4215 kJmol−1 .

Find ΔrU of the reaction.

Answer 1

dU = q + work
q = -4215 kJ/mol x 2 mol = ?
2C6H14 + 19O2 ==> 12CO2 + 14H2O
work is pdV. I assume p = 1 atm. dV is -7 mol x 22.4 L/mol = ?
Since the volume is contracting then the surroundings are doing work on the system; therefore, work will be negative. Substitute and solve.