Question

Calculate the standard enthalpy change for the reaction: CuSO4 (aq) + 4NH3 (aq) -> Cu(NH3)4SO4 (aq) given that the standard enthalpy changes of formation for CuSO4 (aq) and NH3 (aq) are -771.5 kJ/mol and -46.19 kJ/mol respectively, and the standard enthalpy change of formation for Cu(NH3)4SO4 (aq) is -2130.4 kJ/mol.

Answer 1

To calculate the standard enthalpy change for the reaction, we can use Hess's Law, which states that the total enthalpy change for a reaction is the sum of the enthalpy changes of formation for the products minus the sum of the enthalpy changes of formation for the reactants.H_reaction =  H_f products  -  H_f reactants For the given reaction:CuSO4  aq  + 4NH3  aq  -> Cu NH3 4SO4  aq H_reaction = [H_f Cu NH3 4SO4 ] - [H_f CuSO4  + 4 * H_f NH3 ]H_reaction = [-2130.4 kJ/mol] - [ -771.5 kJ/mol  + 4 *  -46.19 kJ/mol ]H_reaction = -2130.4 kJ/mol + 771.5 kJ/mol + 4 * 46.19 kJ/molH_reaction = -2130.4 kJ/mol + 771.5 kJ/mol + 184.76 kJ/molH_reaction = -1174.14 kJ/molThe standard enthalpy change for the reaction is -1174.14 kJ/mol.