The following is a thermochemical question for the combustion of 1-pentene where environment conditions are at 15.4°C.

Question

2C5H10(l) + 15O2(g) → 10H2O(g) + 10CO2(g) + 6318kJ

If 15MJ of energy were to be released in the process of burning 1-pentene, what mass of

the fuel was used?

Answer 1

2C₅H₁₀(l) + 15O₂(g) → 10H₂O(g) + 10CO₂(g) + 6318kJ .. balanced thermochemical equation

We can use the stoichiometry of the balanced equation along with dimensional analysis, to find the answer.

For each 2 moles of C₅H₁₀, we see that 6318 kJ of energy are released (appears as a product).

15 MJ x 1000 kJ / MJ = 15,000 kJ

15,000 kJ x 2 mols C₅H₁₀ / 6318 kJ = 4.7483 mols C₅H₁₀

4.7483 mols C₅H₁₀ x 70.14 g / mol = 333.0 g C₅H₁₀

Usually, we do this calculation in one continuous series, as follows:

15 MJ x 1000 kJ / MJ x 2 mols C₅H₁₀ / 6318 kJ x 70.14 g / mol = 333.0 g C₅H₁₀