Complete combustion of 75.0 g acetylene,C₂H₂,liberated 3750 kJ of heat.What is the heat of combustion,Δ_rH_comb,of acetylene?

Question

Quizplus · Accepted Answer

The heat of combustion is the amount of heat released when one mole of a substance is completely burned. Given that 75.0 g of acetylene releases 3750 kJ, we first need to calculate the moles of acetylene burned. The molar mass of acetylene (C2H2) is approximately 26.04 g/mol (12*2 + 1*2). Thus, 75.0 g corresponds to 75.0 / 26.04 ≈ 2.88 moles. The heat of combustion per mole is then 3750 kJ / 2.88 moles ≈ 1302 kJ/mol. Since combustion releases heat, the sign is negative, indicating an exothermic process. Therefore, the correct answer is -1302 kJ/mol.

Complete Combustion of 75