The standard enthalpies of formation, ΔH∘fΔHf∘, for C2H2(g), O2(g), CO(g), H2O(g), and CO2(g) are given in the table. Use this information to calculate the overall heat of the reaction that converts 1 mole of C2H2(g) and a stoichiometric amount of O2(g).?

...into CO(g) and H2O(g). Hint: Start by writing a balanced thermochemical equation for the reaction.

Compound ΔH∘fΔHf∘ (kJ/mol)
C2H2(g) 226.7
O2(g) 0.0
CO(g) –110.5
H2O(g) –241.8
CO2(g) –393.5

1 Answer
Ernest Z.
Nov 9, 2017

#Δ_text(rxn)H^@ = "-689.5 kJ"#

Explanation:

You can calculate the enthalpy change of a reaction by using the enthalpies of formation of reactants and products.

The formula is

#color(blue)(bar(ul(|color(white)(a/a)Δ_text(rxn)H° = Δ_text(f)H°_text(products) - Δ_text(f)H°_text(reactants)color(white)(a/a)|)))" "#

We have

#color(white)(mmmmmmmmm)"C"_2"H"_2"(g)" + "1.5O"_2"(g)" → "2CO(g)" + "H"_2"O(g)"#
#Δ_text(f)H^°"/kJ·mol"^"-1": color(white)(ml) 226.7color(white)(mmmll)0color(white)(mmmmll)"-110.5"color(white)(mm)"-241.8"#

#Δ_text(rxn)H^° = "[2×(-110.5) + 1×(-241.8)) - 1×226.7] kJ" = "-689.5 kJ"#

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