Question

Give the oxidation number of sulfur in the following:

SOCl₂

H₂S₂

H₂SO₃

Na₂S

Answer 1

To calculate oxidation number of sulphur in given compounds first let's understand how to derive an equation. Take oxidation number (O.N.) of Oxygen =-2, O.N. of H = +1, O.N. of any halogen (not always!) = -1, O.N. of Na, Li etc = +1.

Let's say in SOCl2 assume x is the O.N. of S. over all charge on the molecule is zero, hence:

O.N. of S + O.N. of O + 2 (O.N. of Cl) = 0

x + (-2) + 2 (-1) = 0

x = +4, thus O.N. of S in SOCl2 = +4.

In H2S2

2(+1) + 2(x) = 0

2x = -2

x = -1, hence, O.N. of S in H2S2 = -1.

In H2SO3,

2(+1) + x + 3(-2) = 0

x = 6-2 = +4, thus, O.N. of S in H2SO3 = +4.

In Na2S,

2(+1) + x = 0

x = -2, hence, O.N. of S in Na2S = -2.