chloride products on the right side of the overall equation, and leaving behind copper-free areas on the newborn PCB. The etching solution eventually becomes saturated with copper (II) oxide ...

and not black like the copper oxide. The equation for this reaction is:copper oxide plus sulphuric acid gives copper sulfate plus water. The starting oxide or carbonate must be insoluble ...

For example: copper carbonate decomposes on heating to make solid copper oxide, which stays in the boiling tube, and carbon dioxide gas, which escapes magnesium reacts with oxygen, gained from the ...