Problem: Methanol (CH3OH) burns in oxygen to form carbon dioxide and water. Write a balanced equation for the combustion of liquid methanol and calculate ΔH, ΔS, and ΔG at 25 °C. Is the combustion of methanol spontaneous?

FREE Expert Solution

Balanced reaction: CH3OH(l) + 3/2 O2(g) → CO2(g) + 2 H2O(g)


Step 1: We can use the following equation to solve for ΔH˚rxn:

ΔH°rxn=ΔH°f, prod-ΔH°f, react

Note that we need to multiply each ΔH˚f by the stoichiometric coefficient since ΔH˚f is in kJ/mol. 

Also, note that ΔH˚f for elements in their standard state is 0.


ΔH°rxn=(1 mol CO2)-393.5 kJ1 mol CO2+(2 mol H2O)(-241.8 kJ1 mol H2O)           -(1 mol CH3OH)-239.2 kJ1 mol CH3OH+0

ΔH°rxn = –637.9 kJ/mol



Step 2: We can use the following equation to solve for ΔS˚rxn:

ΔS°rxn=S°f, prod-S°f, react

Note that we need to multiply each S˚ by the stoichiometric coefficient since S˚ is in J/mol • K.

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Problem Details

Methanol (CH3OH) burns in oxygen to form carbon dioxide and water. Write a balanced equation for the combustion of liquid methanol and calculate ΔH, ΔS, and ΔG at 25 °C. Is the combustion of methanol spontaneous?

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