Please help. Someone already asked this but for some reason the answer won't show. 1. Write a balanced chemical equation for each double replacement reaction that occurs. Note: Compounds with Na+, K+, and/or NO3− are soluble. 2. Why was there no reaction in some of the wells? (See Introduction.) 3. How could you tell a Ca(NO3)2 solution from a Zn(NO3)2 solution? 4. How could you tell a Cu(NO3)2 solution from a Ni(NO3)2 solution?