Chemistry exam - please help!

oh_schist

Hi,

I've a Chemistry exam tomorrow and was wondering if anyone could tell me how you would do this question, or point me in the right direction!

Thanks!

A voltaic cell is constructed with a Zn/Zn2+ half cell and a Cu/Cu2+ half cell. The copper electrode is positive. Write half-balanced equations and the overall reaction.

craggles

That sounds a lot like Robert O'Neill's stuff in UCD. If it is it's right there in his notes but I can't remember it off the top of my head.

Reenakjr

Hi,
Oxidation (and reduction) is a competition for electrons. The oxidising species (agents) remove electrons from other species and can force them to become reducing agents (releasers of electrons)
A good example of this competition for electrons is the behaviour of metals. Metals always react by losing electrons (oxidation) they are then reducing agents. However if a metals is in competition with metal ions the more reactive metal can oblige the less reactive metal (in the form of ions) to accept electrons. This is called a displacement reaction.
Example
Zinc reacts with a solution containing copper ions. The zinc metal is more reactive than copper metal and so it can force the copper metal ions to accept electrons and become metal atoms.

Zn(s) Zn2+(aq) + 2e

Cu2+(aq) + 2e Cu(s)

The zinc metal passes its electrons to the copper ions. We observe that the zinc develops a pink layer of coper on its surface and the blue copper ion solution fades in colour.
We say that the zinc displaces the copper ions from solution.