Question

Use the 1/2 reaction method to balance the equation below in acidic solution.
Cl2 (g) + I- (aq) = Cl- (aq) + IO3- (aq)

Answer 1

i don't understand how to do this one. help would be appreciated :)

Answer 2

Here is the I^- ==> IO3^-
1. oxidation number of I is -1 on the left; +5 on the right.

2. Add electrons to the appropriate side. That is
I^- ==> IO3^-+ 6e

3. Add up the charges and add H^+ to balanced the charge. I see -1 on the left side and -7 on the right.
I- ==> IO3^- + 6e + 6H^+
(Check this to see that -1 charge on left is same as -1 charge on right.

4. Now add H2O to the appropriate side (USUALLY but not always) the opposite side from the H^+ addition)
I^- + 3H2O ==>IO3^- + 6e + 6H^+

The Cl half is much easier. If you have any questions about the I^-/IO3^- please let me know. Thos steps will get it done every time. By the way, for basic solutions you add up the charge on step 3 and <b> add OH^- to balance the charge.</b> Everything else is the same.

Answer 3

Hi DrBob222, I tried to finish it and as a final answer I got:
1/2 H2O + Cl2 + I- = Cl- +IO3- + 3H+ ?

Could you please tell me if this is correct? :)

Answer 4

Sorry I didn't get back sooner. It is not.
My half cell is correct.
The Cl should be
2e + Cl2 ==> 2Cl^-

Multiply my eqn by 1 and the Cl by 3 to end up with
I^- + 3H2O + 3Cl2 ==> IO3^- + 6H^+ + 6Cl^-

Check it.
1 I on each side
3O on each side
6H on each side
-1 charge on left and right.

atoms balance
charges balance
electrons (6 for each half cell) balance.
Everything OK.

I don't understand why you changed the 6H^+ I had to 3. and why 1/2H2O instead of the 3H2O? I suspect you DID NOT balance the electrons. There were 6 on my half cell and 2 on yours so you needed to multiply your half cell by 3 before adding it to mine. You should know your equation isn't right by checking it.
1 H on left and 3 on right.
1/2 O on left and 4 on right.
Charge on left is -1; on right is +1.
So atoms don't balance and charge doesn't balance. Repost as a NEW post if you have questions because your question will so far down the line that they sometimes get lost. This isn't difficult but it takes a little discipline to work on it.