very hard redox question

[ahamdi2]

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So im pulling this question from the Princeton Review workbook 2006. its passage 8 of the general chemistry section.

Q) Although zinc metal is attacked by hydrochloric acid in the reaction
Zn (s) + 2 HCl (aq) --> ZnCl2 (aq) + H2 (g)

Copper metal is unaffected by HCl. Why?

A. Cl- is a better oxidizing agent than zinc, but is not a better oxidizing agent than copper
B. Zinc is a better oxidant than copper
C. Zinc is a better oxidant than H+
D. Cu+ is a better oxidant than H+

The answer is D

THE EXPLANATION IS UNCLEAR, can someone provide me with a clear explanation please. Thanks ahead of time

Also the passage talks about reducing and oxidizing agents in ways that i havent heard before
like: Oxidizing agents always has at leasttwo highly electronegative elements covalently bonded together and has a nonnegative oxidation state
and Reducing agents have at least two electropositive atams covalently bonded together and a non-positive oxidation state..

Can someone please explain that two. I always remembered reducing agents as those that can donate hydrogen, and oxidizing agents as ones that can accept hydrogen

 

[deleted329605]

So if something is a powerful oxidizing agent than it likes to gain electrons from whatever species it is oxidizing thus reducing itself. In the reaction between zinc and acid, H+ has a higher affinity for the electrons than does Zinc (you can figure this out by looking at reduction potentials) and because zinc is starting off with all the electrons (its in its metal state) electrons will be transferred and zinc will get oxidized to Zn2+ and H2 gas will evolve.

The question tells you that when mixing copper and H+ no reaction is observed. Thus Copper ion has a higher affinity for electrons than does H+, so copper stays in its reduced metal state, and H+ doesnt become H2 gas.

Another way of saying this is that Copper is a better oxidant or oxidizing agent than H+ because it keeps it electrons and no reaction is performed.

Actually, they way the worded the answer is a little funky, because I'm pretty sure Cu is a poor oxidizing agent because it can't get reduced anymore (it can't take on a negative charge) so maybe a better answer would be that Cu ion is a better oxidant that H+.

Hope this helps

 

[ahamdi2]

Oh !!! i see how that works now, god i haven't touched redox chemistry in a long time i forgot to analyze the H+ and Zn to see which is a stronger oxidizing agent. That helped big time. Thank you so much