14.3

[Jessica Wakefield 1H]

How do you know which element is oxidizing and which is reducing? It looks like they are both gaining electrons so I'm confused.

[Tiffany Dao 1A]

You have to compare it to the connected element. For example, oxygen is 2-, so for part a S2O3 2- , oxygen is 3x2=6 and there's still 2-, so S2 = +4 and S= +2
On the other side, oxygen us 4x2=8 and there's 2-, so S = +6. This means that it gave up electrons. Also, Cl2 has no overall charge, but ends up with Cl-, meaning that each Cl molecule gained one electron. This is like the general idea, not exactly balanced yet, but that's why we do the half-reactions. Just a reminder that H+ and H2O are also being used to balance the equation. I hope that helped