Consider the thermochemical equation: 2C₂H₆(g) + 7O₂(g) → 4CO₂(g) + 6H₂O(ℓ) ; ΔH = -3,120 kJ
How much energy is given off when 45.0 g of C₂H₆ and 96.0 g of oxygen are reacted? (Molar masses: C₂H₆ = 30.0 g; O₂ = 32.0 g)

Question

Quizplus · Accepted Answer

First, determine the limiting reactant. For CS₂H₆, 45.0 g / 30.0 g/mol = 1.5 moles. For O₂, 96.0 g / 32.0 g/mol = 3.0 moles. According to the stoichiometry of the reaction, 2 moles of CS₂H₆ react with 7 moles of O₂. Therefore, CS₂H₆ is the limiting reactant. The reaction of 2 moles of CS₂H₆ releases 3,120 kJ, so 1.5 moles will release (3,120 kJ * 1.5 moles) / 2 moles = 1,560 kJ. However, since the question asks for the energy given off, and considering the stoichiometry, the calculation should reflect the proportional amount of energy released based on the actual amount of CS₂H₆ reacted. The correct calculation is (3,120 kJ * 1.5 moles) / 2 moles = 2,340 kJ, indicating a mistake in my explanation regarding the final calculation. The correct approach is to find the amount of energy released per mole of the limiting reactant and then multiply by the number of moles of the limiting reactant used. Given the error in calculation, the correct answer should reflect the energy released based on the limiting reactant's moles, which was initially calculated as 1,560 kJ for 1.5 moles of CS₂H₆, but the correct calculation should actually consider the stoichiometry properly. The mistake was in the final step of the calculation; the correct answer should be derived from the proportion of the limiting reactant used in the reaction.

Consider the Thermochemical Equation: 2C2H6(g) + 7O2(g) → 4CO2(g)

Consider the Thermochemical Equation: 2C₂H₆(g) + 7O₂(g) → 4CO₂(g)