Selective Oxidation

1. Nov 25, 2007

salman213

1. The standard reduction potential for the half-reaction

Sn4+ + 2e- Sn2+
is +0.15 V.
Consider data from the table of standard reduction potentials for common half-reactions, in your text.

For a galvanic cell under standard conditions, which of the following cathodic half reactions would produce, at the anode, a spontaneous oxidation of Sn to Sn2+ but not Sn2+ to Sn4+.

Sn2+ + 2e- Sn
Pb2+ + 2e- Pb
2H2O + 2e- H2 + 2OH-
PbSO4 + 2e- Pb + SO42-
Fe2+ + 2e- Fe
Fe3+ + 3e- Fe

HOW DO I APPROACH THIS PROBLEM?

2. Nov 25, 2007

salman213

any help >

3. Nov 25, 2007

ace123

Well what are your thoughts on the problem. Also it seems kind of obvious from your choices think about it..

4. Nov 26, 2007

salman213

Im not really sure how to approach this , i gues i have to look at standard potentials but im not sure what the question is asking me.

5. Nov 26, 2007

salman213

Ok im confused this is wat i did
Sn4+ + 2e- Sn2+
is +0.15 V.

For a galvanic cell under standard conditions, which of the following cathodic half reactions would produce, at the anode, a spontaneous oxidation of Sn to Sn2+ but not Sn2+ to Sn4+.
Sn2+(aq) + 2e− → Sn(s) −0.13

Sn2+ + 2e- Sn -0.13 V
No not spontaeous this is at equilibirum?

Pb2+ + 2e- Pb 0.13 V
Yes because it is spontaneous and the Sn2+ to Sn4+ will occur at the cathode

2H2O + 2e- H2 + 2OH- -0.828 V
No because this will occur at anode since more negative

PbSO4 + 2e- Pb + SO42- -0.359 V
No because this will occur at anode since more negative

Fe2+ + 2e- Fe −0.44 V
No becuase this will occur at anode since more negative

Fe3+ + 3e- Fe -0.04 V
Yes the Sn will be oxidized to Sn2+ since it has lower potential -.13 and it is spontaneous and also the Sn2+ to Sn4+ will not happen at anode since it is much more postive.

I ONLY HAVE 1 MORE TRY TO GET IT RIGHT ON MY ASSIGNMENT ONLINE PLZ HELPPPPPPPPPPPPPPP

Last edited: Nov 26, 2007
6. Nov 26, 2007

salman213

I think these are right but I dont want to submit them before making sure with someone smart at this forum since i only have one chance left.... lol :)