The heat combustion of gaseous butane is -2658 kl/mol and the heat of combustion of liquid butane is:

The heat of combustion of liquid butane is: -2636 kJ/mol

Explanation:

This problem is solved by using Hess law of heats summation:

We have the heat of combustion for gaseous butane:

C₄H₁₀ (g) + 13/2 O₂ (g) ⇒ 4 CO₂ (g) + H₂O (l)     ΔHºcomb = -2658 kJ/mol

and we want the heat of combustion for liquid butane.

What we need to do is add the heat of vaporization for liquid butane to this equation:

C₄H₁₀ (l)   ⇒  C₄H₁₀ (g)   ΔHºvap =  22.44 kJ/mol

C₄H₁₀ (g) + 13/2 O₂ (g) ⇒ 4 CO₂ (g) + H₂O (l)  ΔHºcomb = -2658 kJ/mol

C₄H₁₀ (l)   + 13/2 O₂ (g) ⇒ 4 CO₂ (g) + H₂O (l)  

So,

ΔH comb liq butane = -2658 kJ/mol + 22.44 kJ/mol = -2636 kJ/mol