Im going to try my best to write out this chemical equation. Also I'm gonna write a forward arrow but it's really it should be the equilibrium arrows. [Co(H2O)6]2+ + 4Cl- --> [CoCl4]2- + 6H2O Sorry for that, I don't know how to use the math font or whatever it's called. The question is whether the reaction is exothermic or endothermic. I think reaction is endothermic. Cobalt chloride is a red color and when we heated a solution of it in the presence of hydrochloric acid it turned a dark blue color. A possible solution I thought of as to why it's endothermic is because energy is required to break the attractions between the cobalt ion and the water molecules. I believe that is called a metal ion complex, correct? I'm very unconfident about this answer. Can I please get some feed back? Thanks.