Question

I need the oxidation half reactions, reduction half reactions, and net ionic equations for the following reactions:
1)magnesium +0.1M zinc sulfate
2)copper+0.1M zinc sulfate
3)zinc+0.1M copper(II)sulfate
4)zinc+3M HCl
5)copper+3M HCl
6)0.1M potassium iodide+ 0.1M copper(II)sulfate
7)0.1M potassium iodide + 0.02M potassium iodate
8)0.1M potassium iodide+ 0.1M potassium ferricyanide
9)0.1M iron(III) chloride + 0.1M potassium iodide
10)0.1M iron(III)chloride +0.1M potassium bromide
11)3% hydrogen peroxide + 0.1M cerium(IV)ammonium nitrate
12)aqueous iodine + 1M sodium thiosulfate

Answer 1

Here is the way you do #1.

Mg(s) + ZnSO4(aq) ==> MgSO4(aq) + Zn(s)
1. How do you know Mg will displace Zn? Look at the activity series. A metal will displace any ion below it. Mg is above Zn; therefore, it will displace Zn^+2. Here is a chart.
http://www.files.chem.vt.edu/RVGS/ACT/notes/activity_series.html

half reactions:
You pick them out. Mg goes to Mg^+2 and Zn^+2 goes to Zn.
Mg ==> Mg^+2 + 2e is oxidation (loss of electrons)
Zn^+2 + 2e ==> Zn is reduction (gain of electrons).
Add the two to obtain the net ionic equation.
Mg(s) + Zn^+2(aq) --> Mg^+2(aq) + Zn(s)

#12.
I2(aq) + 2Na2S2O3 ==> 2I^- + 4Na^+ = S4O6^-2

I2 + 2e ==> 2I^- reduction
2S2O3^-2 ==> S4O6^-2 + 2e oxidation

net ionic:
I2(aq) + 2S2O3^-2(aq) ==> 2I^-(aq) + S4O6^-2(aq)

Answer 2

Mg(s) + ZnSO4(aq) ==> MgSO4(aq) + Zn(s)
1. How do you know Mg will displace Zn? Look at the activity series. A metal will displace any ion below it. Mg is above Zn; therefore, it will displace Zn^+2. Here is a chart.