Problem: The standard enthalpies of formation of gaseous propyne (C3H4), propylene (C3H6), and propane (C3H8) are +185.4, +20.4, and -103.8 kJ/mol, respectively.Calculate the heat evolved per mole on combustion of each substance to yield CO2(g) and H2O(g).

FREE Expert Solution

ΔH°rxn=ΔH°f, prod-ΔH°f, react


C3H4(g) + 4 O2(g) → 3 CO2(g) + 2 H2O(g).

ΔH°rxn=(3 mol CO2)-393.5 kJ1 mol CO2+(2 mol H2O)(-241.8 kJ1 mol H2O)           -(1 mol C3H4)+185.4 kJ1 mol C3H4+0

ΔH˚rxn = –1849.5 kJ/mol


C3H6(g) + 9/2 O2(g) → 3 CO2(g) + 3 H2O(g).

ΔH°rxn=(3 mol CO2)-393.5 kJ1 mol CO2+(3 mol H2O)(-241.8 kJ1 mol H2O)           -(1 mol C3H6)+20.4 kJ1 mol C3H6+0

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Problem Details

The standard enthalpies of formation of gaseous propyne (C3H4), propylene (C3H6), and propane (C3H8) are +185.4, +20.4, and -103.8 kJ/mol, respectively.

Calculate the heat evolved per mole on combustion of each substance to yield CO2(g) and H2O(g).

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