Thermochemistry. Answer, step by step please. (show work)

Question

Combustion of C8H18(g) ∆H = -5076 kJ

a. Write a balanced chemical equation that includes heat as a reactant or product.

b. What volume of products can be made if 120 kilojoules are released?

Answer 1

a. 2C₈H₁₈ + 25O₂ ==> 16CO₂ + 18H₂O + heat

b. The problem states ∆H = -5076 kJ, but it should more properly state -5076 kJ/mol. Using this value, we answer part b as follows:

120 kJ x 1 mol C₈H₁₈ / 5076 kJ x 16 mol CO₂ / 2 mol C₈H₁₈ = 0.189 mols CO₂

120 kJ x 1 mol C₈H₁₈ / 5076 kJ x 18 mol H₂O / 2 mol C₈H₁₈ = 0.213 mols H₂O

The problem doesn't state the conditions so to find the volume of each gaseous product, we'll have to assume STP. At STP, 1 mol of an ideal gas occupies 22.4 liters.

Volume CO₂ = 0.189 mols x 22.4 L / mol = 4.23 L

Volume H₂O = 0.213 mols x 22.4 L / mol = 4.77 L