Chemistry - Redox Reactions Question with Solution | TestHub

To find the oxidation numbers of sulfur in Na₂S₂O₅:

1. Assign known oxidation numbers: Na = +1, O = -2.

2. Let the oxidation number of sulfur be $x$.

3. Sum of oxidation numbers in a neutral compound is zero: $2(+1)+2(x)+5(-2)=0$.

4. Solve for $x$: $2+2x-10=0\Rightarrow 2x=8\Rightarrow x=+4$.

However, this is an average. Na₂S₂O₅ has a thiosulfate-like structure with a S-S bond. One sulfur is +5, the other is +3.

The difference is $5-3=2$.