Redox Questions

[darkphoenix]

Cause i forgot alot of this stuff..

Complete the following reactions:

1. A redox reaction occurs when zinc dissolves in sulfuric acid.
a) Balanced
b) Redox (Oxidation)
c) Redox (Reduction)

2. An iron nail is placed in acidified potassium dichromate (K2Cr2O7) solution. The chromium in the dichromate ion is reduced to Cr3+ and the iron corrodes to Fe2+ ion.
a) Redox (Oxidation)
b) Redox (Reduction)
c) Ionic (redox combined)

Thanks.

[slothpomba]

You'd probably remember it much better if you flicked through your chemistry book and learnt how to do it all over again.

(I say this because i dont have an answer ... i forgot too)

[chem-nerd]

1.
Zn(s) + H₂SO₄(aq) -> ZnSO₄(aq) + H₂(g)

Zn(s) -> Zn²⁺(aq) + 2e

2H⁺(aq) + 2e -> H₂(g)

2.
Fe(s) -> Fe²⁺(aq) + 2e

Cr₂O₇^2-(aq) + 14H⁺(aq) + 6e -> 2Cr³⁺(aq) + 7H₂O(l)

3Fe(s) + Cr₂O₇^2-(aq) + 14H⁺(aq) -> 3Fe²⁺(aq) + 2Cr³⁺(aq) + 7H₂O(l)

[darkphoenix]

Yeah hahah problem is i already sold it and my notes are all a mess.

Thanks chem-nerd.

EDIT: Got another question:

2S₂O₄^2-(aq) + H₂O(l)  ->  S₂O₃^2-(aq) + 2HSO₃^-(aq)

What would be the Reduction and Oxidation half equations?

Cheers.

[chem-nerd]

S₂O₄^2-(aq) + 2H⁺(aq) + 2e -> S₂O₃^2-(aq) + H₂O(l)

S₂O₄^2-(aq) + 2H₂O(l) -> 2HSO₃^-(aq) + 2H⁺(aq) + 2e

Then when you combine them you can cancel out the 2e and 2H⁺ on both sides and one of the H₂O on both sides

Also, didn't you keep an ecopy of your textbook before you sold it?

[superflya]

ey chem nerd, wen did u do 3&4 chem?

[darkphoenix]

S₂O₄^2-(aq) + 2H⁺(aq) + 2e -> S₂O₃^2-(aq) + H₂O(l)

S₂O₄^2-(aq) + 2H₂O(l) -> 2HSO₃^-(aq) + 2H⁺(aq) + 2e

Then when you combine them you can cancel out the 2e and 2H⁺ on both sides and one of the H₂O on both sides

Also, didn't you keep an ecopy of your textbook before you sold it?

Haha nope, thanks again.

Do you happen to have it?