Question

Calculate ΔH∘ in kilojoules for the reaction of acetylene (C2H2) (ΔH∘f=227.4kJ/mol) with O2 to yield carbon dioxide (CO2)(ΔH∘f=−393.5 kJ/mol) and H2O(g) (ΔH∘f=−241.8kJ/mol), a reaction which is supplied by the industrial gases industry for oxyacetylene gas welding and cutting due to the high temperature of the flame.

2C2H2(g)+5O2(g)→4CO2(g)+2H2O(g)

Express your answer using one decimal place.

Answer 1

_fH⁰ C₂H₂ = 227.4 KJ/mol

_fH⁰ O_2(g) = 0 KJ/mol

_fH⁰ CO_2(g) = -393.5 KJ/mol

_fH⁰ H₂O_(g) = -241.8 KJ/mol

H⁰ = _fH⁰ (Product) - _fH⁰ (Reactant)

H⁰ = [(4_fH⁰ CO₂) + (2_fH⁰ H₂O)] - [(2_fH⁰ C₂H₂) + (5_fH⁰ O₂)]

= [(4 (-393.5)) + (2 (-241.8))] - [2(227.4) + (5 (0)]

= [-2057.6] - [454.8]

H⁰ = -2512.4 KJ/mol

H⁰ for reaction = -2512.4 KJ/mol