[phen0l]

I am stuck on this exam question, any help will be much appreciated!

The question ask's why acid reacts with zinc but not copper.
Also what is the oxidizing agent in the reaction?

The question provides a half-cell/E cell value table.

Zn2+    +    2e-   -->   Zn      -0.76

Cu2+    +    2e-   -->   Cu      +0.34

Ag+      +     e-   -->   Ag      +0.80



I have the answer but can someone explain why this is happening??
Answer:
* H+ is the oxidizing agent
* This is because Zn is going to Zn2+
* Hydrogen half-cell is 0 - Only negative electrode will get oxidized

 

[Vidya]

Compare the reactivity of H and Cu .Cu is more powerful oxidizing  agent then H because its reduction potential is more than H .Hence Cu can oxidize H but it can not reduce H+ present in HCl
high reduction potential--- strong oxidizing agent. 

[vmelkon]

It is more complicated than that. The anion of the acid does have an effect. For example, nitric acid reacts with copper.
Nitric acid reacts with silver.
Nitric acid + HCl reacts with gold.

You can look at the explanation at the bottom here, for Cu + HNO3
http://www.chem.umn.edu/services/lecturedemo/info/Acid_Rain.html

[Arkcon]

Exactly, for example nitric acid and sulfuric acid both have some oxidizing ability from their anion.  HCl is the strong acid with almost no oxidizing ability, just the reducing power of it's acid hydrogen.

[Borek]

It is more complicated than that.

In this particular case (HCl solution) there is no need to look for any more advanced explanation, as the only oxidizing agent present is H⁺. So while you are right about the existence of oxidizing acids they don't play any role here - and as such IMHO should be not mentioned to not muddy the water.

[Borek]

the reducing power of it's acid hydrogen.

You may want to rethink that statement 

[Arkcon]

Dang we need an embarrassment icon.  I really meant that hydrochloric acid has the least oxidizing power of the other acids I mentioned.  What I said doesn't make a whole lot of sense, does it?