Oxidixing & reducing agents

[pmandola]

Identify the oxidizing & reducing agent in each
a)
2[MnO₄]-(aq) + 10[Cl]-(aq) + 16[H]+(aq) =
2[Mn]₂+(aq) + 8H₂O(l)

b)
8[H]+(aq) + [Cr₂O₇]₂-(aq) + 3[SO₃]₂-(aq) =
2[Cr]₃+(aq) + 3[SO₄]₂-(aq) + 4H₂O(l)

[jaelen]

Ok, well first of all you need to remember that oxidizing agents are being reduced while reducing agents are oxidized.

If you can't remember which is which just think of it this way: LEO the lion goes GER:

LEO- Loss of electrons is oxidation
GER- Gain of electrons is reduction

a) I'll take a guess, but I'm wondering where your Cl went.
[MnO₄]- = oxidizing agent, the Mn goes from 8+ to 2+ so it's reduced
[Cl]- = reducing agent, chlorine will lose electrons to Mn and so is oxidized
---> the change in oxidation numbers for [O] and [H]+ remain unchanged so they are not included

b) [Cr₂O₇]₂- = oxidizing agent because Cr goes from 6+ to 3+ so it is reduced
[SO₃]₂- = reducing agent because the oxidation number for S goes from 2+ to 4+ and so is being oxidized


It's been a while since I've done an exercise like this one so I might be wrong, but the theory i provided above is correct. I hope this helps

[pmandola]

You were right on!

Still is a bit confusing to me but will help get through homework so that I can go back and review for tests. Ugh.

Thanks!

[jaelen]

No problem. I need the review anyhow

And I know how you feel, that was one of my worst units in high school, I could never emember which was which.