Using the following thermochemical equation, determine the amount of heat produced from the combustion

Question

Using the following thermochemical equation, determine the amount of heat produced from the combustion of 19.6 g benzene (C₆H₆). The molar mass of benzene is 78.11 g/mole.

 2 C₆H₆(l) + 15 O₂(g) → 12 CO₂(g) + 6 H₂O(g) ΔH°_rxn = -6278 kJ

Answer 1

s the heat of combustion isn't expressed in kj/mole, and values I found on the internet are about half what you specified, I have to assume the value you have given is in kilojoules for 2 moles of benzene.

The number of moles of benzene used is 19.6 g / 78.11 g/mole = 0.251 moles.

The calculation is -6278 kj/ 2mole x 0.251moles = 788 kj to 3 sig figs.