Question

What is the enthalpy of combustion (per mole) of C₄H₁₀ (g)?

1) -2,657.5 kj/mol
2) -5315.0 kj/mol
3) -509.7 kj/mol
4) -254.8 kj/mol

Answer 1

The enthalpy of combustion of butane, C4H10(g), for the formation of H2O(g) and CO2(g) is -5315.0 kJ/mol.

Step-by-step explanation:

The enthalpy of combustion is the amount of heat released when one mole of a substance undergoes complete combustion in excess oxygen. To calculate the enthalpy of combustion of butane, C4H10(g), we need to use the enthalpy of formation of butane and the enthalpies of formation of water and carbon dioxide. The balanced equation for the combustion of butane is: C4H10(g) + 13/2 O2(g) -> 4 CO2(g) + 5 H2O(g)

Given that the enthalpy of formation of butane is -126 kJ/mol, and the enthalpies of formation of water and carbon dioxide are -286 kJ/mol and -394 kJ/mol respectively, we can calculate the enthalpy of combustion using Hess's law:

Enthalpy of combustion = (4 * -394 kJ/mol) + (5 * -286 kJ/mol) - (-126 kJ/mol)

Enthalpy of combustion = -5314 kJ/mol

So, the correct answer is option 2) -5315.0 kJ/mol.