A reaction will NOT occur when all the reactants and products in the ionic equation are spectator ions because no change occurs such as the formation of a precipitate or molecular compound. Which of the following combinations (as reactants) will NOT undergo chemical change when mixed? Refer to Appendix J if needed. Mg(NO3)2(aq) and NaOH(aq) HCl(aq) and NaOH(aq) NaNO3(aq) and KI(aq)