Oxidation number of Sulfur in H2SO3
The oxidation number of sulfur in H2SO3 is +4.
In H2SO3, hydrogen has an oxidation number of +1. So, in two molecules of H2SO3, hydrogen has an overall oxidation number of +4.
Since the overall charge of H2SO3 is 0, the sum of the oxidation numbers of the atoms must equal 0. The oxidation number of oxygen is usually -2, but here it is -1 to balance with the positive oxidation number of hydrogen.
So, let x be the oxidation number of sulfur:
2(+1) + x + 3(-1) = 0
Simplifying the equation, we get:
2 + x - 3 = 0
x - 1 = 0
x = +1
Therefore, the oxidation number of sulfur in H2SO3 is +1.