Electroplating with baking soda. What is this solution?

Question

I added sodium bicarbonate to hot water. It bubbled for a while. Then I hooked it up to a battery with copper electrodes. After a few minutes the solution was bright blue. I was able to easily electroplate several items with copper in this solution. What is it?

Answer 1

If your anode was made of copper, then this would have dissolved as the electrolysis proceeded:

Cu -----> Cu2+ + 2e-

So the electrolyte would have been copper hydrogencarbonate, Cu(HCO3)2.