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.Which is the most efficient fuel in terms of heat evolved per unit mass?

🤓 Based on our data, we think this question is relevant for Professor Laskin & Ren's class at PURDUE.

FREE Expert Solution

For propyne (C3H4)

C3H4 + 4 O2 → 3 CO2 + 2 H2O


ΔH°rxn=H°f, prod-H°f, react

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


molar mass propyne = 40.062 g/mol

H°rxn=-1849.5kJmol×mol40.062 g

ΔH˚rxn = –46.16 kJ/g



For propylene (C3H6)

C3H6 + 9/2 O2 → 3 CO2 + 3 H2O

ΔH°rxn=H°f, prod-H°f, react

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

View Complete Written Solution
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.

Which is the most efficient fuel in terms of heat evolved per unit mass?

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Enthalpy of Formation concept. You can view video lessons to learn Enthalpy of Formation. Or if you need more Enthalpy of Formation practice, you can also practice Enthalpy of Formation practice problems.

What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Laskin & Ren's class at PURDUE.