Using Hess's Law and the values for Standard Enthalpies of Formation from the table provided, calculate the enthalpy of reaction AHr Orxn (in kJ) for the following reaction with the appropriate sign: (express answer as a number with appropriate sign) Standard Enthalpies of Formation substance AHin kJ/mol Mg(s) 0 MgO(s) -601.6 HCl(aq) -167.2 MgCl2(aq) -801.2 H2(g) 0 H2O(1) -285.8 Reaction #2: MgO (s) + 2HCl (aq) => MgCl2 (aq) + H20 (1)