Question

Propyne C3H4 has standard heat of formation +185.4 kJ/mole. Calculate the heat given off when one mole of propyne is combusted. Show balance combustion reaction.

Answer 1

The equation of the reaction is C₃H₄ + 4O₂ = 3CO₂ + 2H₂O

Heat given off= heat of combustion = Enthalphy change of the reaction

ΔH= ΔH_fproducts - ΔH_freactants

Heat of formation of H₂O=-241.8KJ

Heat of formation of CO₂= -393.5KJ

Heat of formation of C₃H₄= +185.4KJ

ΔH= [(3×CO₂)+(2×H₂O) ] - [(C₃H₄)+ (4×O₂)]

ΔH= [ (3×-393.5KJ) + (2 ×-241.8KJ) - [ 185.4KJ + 0]

ΔH= [ 1180.5KJ - 483.6KJ] - 185.4KJ

ΔH= -1164.1KJ - 185.4KJ

ΔH= -1849.5KJ

The heat given off when one mole of propyne is combusted is -1849.5KJ