Question

During the combustion of 5.00 g of octane, C8H18, 239.5 kcal is released. How much energy is released by the combustion of 1.54 mol of C8H18 ?

Answer 1

Explanation:

Molar mass of $C_{8}H_{18}$ is 114.23 g/mol. Therefore, its number of moles are calculated as follows.

       No. of moles = $\frac{mass}{\text{molar mass}}$

                             = $\frac{5 g}{114.23 g/mol}$

                             = 0.043 mol

So, 0.043 moles are releasing 239.5 kcal of heat. Hence, heat released by 1.54 mol will be calculated as follows.

           $\frac{239.5 kcal}{0.043 mol} \times 1.54 mol$

               = 8577.44 kcal

Thus, we can conclude that 8577.44 kcal heat is released by the combustion of 1.54 mol of $C_{8}H_{18}$.