Does Copper's Oxidation State Need Specification in Chemical Reactions?

[student34]

Homework Statement

A student performs a single replacement reaction by dipping a strip of copper metal, Cu(s), into an aqueous solution of silver nitrate, AgN0₃(aq), to produce silver, Ag(s). Write the balanced equation.

Homework Equations

The Attempt at a Solution

The answer has, 2AgN0₃(aq) + Cu(s) = 2Ag(s) + Cu(N0₃)₂(aq).

This only makes sense to me if it is copper II metal. Doesn't it have to specify? How else would I know?

I know that there is some naming rule that says something about if there is nothing specified, then it is one or the other. But I have seen copper II specified before.

 

[Bystander]

How else would I know?

This is among a whole lot of other information that just has to stick in your memory. "The plus II oxidation state for Cu" is the one you commonly encounter. There isn't any convincing argument for stability of nine electrons in the 4s and 3d orbitals (Cu⁺²) being greater than that of ten electrons (Cu⁺), so don't feel you've missed seeing something that should be obvious to you --- it isn't obvious to anyone.

 

[student34]

This is among a whole lot of other information that just has to stick in your memory. "The plus II oxidation state for Cu" is the one you commonly encounter. There isn't any convincing argument for stability of nine electrons in the 4s and 3d orbitals (Cu⁺²) being greater than that of ten electrons (Cu⁺), so don't feel you've missed seeing something that should be obvious to you --- it isn't obvious to anyone.

Shouldn't they have put "copper II" instead of just "copper"? That is what throws me off.

 

[Borek]

No, no need for that. Cu(I) is quite rare. You may expect Cu(I) in questions related to some quite specific copper chemistry, but not when it comes to a general copper reaction in the solution.