Question

When dissolved in water, Cu2+ often forms the complex [Cu(OH2)6]2+. What is the oxidation state of Copper?

Answer 1

Well, consider the charge on what is surrounding copper. How else can you write `"OH"_2`? Does it remind you of a certain neutral solvent? Does the oxidation state of copper therefore change from `+2`, where it started?

`[stackrel(color(blue)(??))("Cu")stackrel(color(blue)(0))(("OH"_2)_6)]^(2+)`