reduction by copper
 

The question simply is, which could be reduced by Cu?
Sn2+ (superscript 2+)
Ag+ (superscript +)
Zn2+ (superscript 2+)

How do i figure this out? ...by using some sort of database?
I know copper will spontaneously reduce Ag+
Not sure about the other 2.

You can to look up reduction potentials for this, or just know the order of of oxidising/reducing power - for high school/secondary school it is useful to have an idea of the relative reactivity of metals.

Here is a simplistic way of approaching the problem

Apart from being cheap, copper is used alot in plumbing because is not too easily oxidised - this means it isn't very reducing. So you have a starting point.
Cu ---> Cu+ ---> Cu2+ is quite a difficult process, generally speaking.

Silver is used in jewelley because it is even more resistant to oxidation, so it stays shiny! This also means that, because it's really difficult to oxidise Ag --> Ag+, it is really easy to reduce Ag+ --> Ag.
You are right about Ag+, copper will reduce it because the ease of reducing Ag+ outweighs the difficulty of oxidising Cu.

You should know that Zinc is pretty reactive - this is because it is easy oxidise. So Zn ---> Zn2+ is easy, which means Zn2+ ---> Zn is difficult.
So Cu will not reduce Zn2+, because it is difficult to reduce Zn2+ AND quite difficult to oxidise Cu - so it doesn't happen.

Tin is mildly reactive, not as reactive as Zn. So it's quite easy to oxidise Sn--> Sn2+, and so Sn2+-->Sn is quite difficult.
So Cu won't reduce Sn2+ because because it is quite difficult to reduce Sn2+ AND quite difficult to oxidise Cu - so it doesn't happen.

I hope that helps!

thanks!