Problem: What is the heat of reaction (ΔH°rxn) for the combustion of acetone (C3H6O) given the following thermochemical equations? (Answer should come out to be ΔH°rxn = −1755 kJ)1. 3 C(s) + 3 H2(g) + ½ O2(g) → C3H6O(ℓ) ΔHf° = −285.0 kJ2. C(s) + O2(g) → CO2(g) ΔHf° = −394.0 kJ3. H2(g) + ½ O2(g) → H2O(ℓ) ΔHf° = −286.0 kJ

FREE Expert Solution

We’re being asked to determine the heat of reaction (ΔH°rxn) for the combustion of acetone (C3H6O) 


The balanced chemical reaction for the combustion of acetone (C3H6O) is


C3H6O (l) + 4 O2 (g)  3 CO2 (g) + 3 H2O (g)



We can use Hess’s Law to determine the enthalpy change of the overall reaction from the given reactions:


1. 3 C(s) + 3 H2(g) + ½ O2(g)  C3H6O(ℓ) ΔHf° = −285.0 kJ
2. C(s) + O2(g)  CO2(g) ΔHf° = −394.0 kJ
3. H2(g) + ½ O2(g)  H2O(l) ΔHf° = −286.0 kJ


We now need to find a combination of reactions that when added up, gives us the overall reaction.

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Problem Details

What is the heat of reaction (ΔH°rxn) for the combustion of acetone (C3H6O) given the following thermochemical equations? (Answer should come out to be ΔH°rxn = −1755 kJ)

1. 3 C(s) + 3 H2(g) + ½ O2(g) → C3H6O(ℓ) ΔHf° = −285.0 kJ

2. C(s) + O2(g) → CO2(g) ΔHf° = −394.0 kJ

3. H2(g) + ½ O2(g) → H2O(ℓ) ΔHf° = −286.0 kJ

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