The complete combustion of butane ( C ₄ H ₁₀ ) gas produces carbon dioxide gas and liquid water. The standard enthalpies of formation of C ₄ H ₁₀ (g) , CO ₂ (g) and H ₂ O(l) are -125 kJ mol ⁻¹ , -393 kJ mol ⁻¹ and -285 kJ mol ⁻¹ respectively. The magnitude of the total heat released when 29 g of butane is completely combusted is ________ kJ . (Given molar mass of C = 12 g mol ⁻¹ , H = 1 g mol ⁻¹ )

Step-by-step solution

The balanced chemical equation for the combustion of 1 mole of butane is: C ₄ H ₁₀ (g) + 13 2 O ₂ (g) 4 CO ₂ (g) + 5 H ₂ O(l) The standard enthalpy of combustion for 1 mole of butane is: H^ _ c = [4 H^ _ f ( CO ₂ , g ) + 5 H^ _ f ( H ₂ O, l )] - [ H^ _ f ( C ₄ H ₁₀ , g ) + 13 2 H^ _ f ( O ₂ , g )] Since H^ _ f ( O ₂ , g ) = 0 : H^ _ c = [4(-393) + 5(-285)] - [-125] H^ _ c = [-1572 - 1425] + 125 H^ _ c = -2997 + 125 = -2872 kJ mol ⁻¹ Molar mass of butane ( C ₄ H ₁₀ ) = 4(12) + 10(1) = 58 g mol ⁻¹ Number of moles in