What is the value of ( H - U) for the complete combustion of liquid benzene at 298 K ? (Given: R = 8.314 J K ⁻¹ mol ⁻¹ )

Step-by-step solution

The balanced chemical equation for the complete combustion of liquid benzene at 298 K is: C ₆ H ₆( l ) + 15 2 O ₂( g ) 6 CO ₂( g ) + 3 H ₂ O ( l ) The change in the number of gaseous moles ( n_g ) is: n_g = n_p( g ) - n_r( g ) n_g = 6 - 15 2 = -1.5 The relationship between enthalpy change ( H ) and internal energy change ( U ) is: H = U + n_g RT H - U = n_g RT Substituting the values: H - U = -1.5 8.314 J K ⁻¹ mol ⁻¹ 298 K H - U = -3716.358 J mol ⁻¹ H - U -3.716 kJ mol ⁻¹ Treating H ₂ O as a gas incorrectly leads t