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Old 11-26-2010, 10:25 PM   #1
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Chemistry?

Which of the following represents a process in which a species is reduced?

(a) Ca(s) → Ca 2+(aq)
(b) Hg(l) → Hg2 2+(aq)
(c) Fe 2+(aq) → Fe 3+(aq)
(d) NO3 –(aq) → NO(g)
(e) SO3 2–(aq) → SO4 2–(aq)

LEO goes GER

For it to be reduced it needs to gain electrons, but none of these things are gaining electrons...
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Old 11-26-2010, 10:29 PM   #2
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Cd2+(aq) + 2 e– →← Cd(s) Eo = -.41 V
Cu+(aq) + e– ←→ Cu(s) Eo = +.52 V
Ag+(aq) + e– ←→ Ag(s) Eo = +.80 V

Eo = –0 .41 V Eo = +0 .52 V Eo = +0 .80 V
15 . Based on the standard electrode potentials given above, which of the following is the strongest reducing agent?

(a) Cd(s) (b) Cd2+(aq) (c) Cu(s) (d) Ag(s) (e) Ag+(aq)

Please explain!
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Old 11-26-2010, 11:28 PM   #3
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1st question:
First of all, gaining electrons is not only the definition of reduction. Losing of oxygen atoms too should be kept in concern and above all decrease in oxidation number is also known as reduction.
Having said that, if we look at all the options,
only D,in which the atom N, where the number of oxygen atoms is decreasing, is undergoing a reduction.......
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Old 11-26-2010, 11:31 PM   #4
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Thanks sammy, I wasn't aware of that alternate definition, but what about #2?
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Old 11-27-2010, 12:07 AM   #5
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For number 2 you should know that the reactions given are for standard electrode potentials and they are the indicators of how easily the reactant (L.H.S) is reduced to the products(R.H.S).Also if one atom reduces then it oxidizes other one. So the less positive the Eo, the difficult it is to reduce and the less oxidising capacity and more reducing capacity it has.
By looking at these facts, I think the correct answer is D Ag(S).....
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Old 11-27-2010, 12:11 AM   #6
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^Thats what I thought too, but the answer is (A). This is from the collegeboard.
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Old 11-27-2010, 12:15 AM   #7
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http://apcentral.collegeboard.com/ap...escription.pdf

Here is where I got the question from.
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Old 11-27-2010, 01:39 AM   #8
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The answer is A because the strongest reducing agent will have the highest oxidation potential and the ones given are standard [reduction] potentials. Flip the sign for oxidation potentials and the highest one is Cadmium's
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Old 11-27-2010, 05:15 PM   #9
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By flipping the signs the highest one is +.41 V. Wouldn't that be Cd 2+, or (B)? Why is it Cd?
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Old 11-27-2010, 05:26 PM   #10
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Lol, 2+ is the highest oxidation state of cadmium. Since Cd 2+ is already is in a oxidation state of 2+, it cannot be further oxidized. So the answer is the metal, Cd.

Reducing agent= thing getting oxidized.
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