For the reaction 2 NO ( g ) + O ₂( g ) 2 NO ₂( g ) at 400 K , the change in internal energy ( U ) is -70 kJ . What will be the enthalpy change ( H ) for the reaction at the same temperature? (Given R = 8.314 J K ⁻¹ mol ⁻¹ )

Step-by-step solution

The given reaction is 2 NO ( g ) + O ₂( g ) 2 NO ₂( g ) The change in the number of moles of gaseous species is: n_g = n_p - n_r = 2 - (2 + 1) = -1 The relation between enthalpy change and internal energy change is: H = U + n_g RT Substituting the given values: H = -70 + (-1) (8.314 10⁻³) 400 H = -70 - 3.3256 H = -73.3256 kJ -73.33 kJ Answer: -73.33 kJ