Question

calculate the oxidation number of sulphur in the following molecules H2SO3 and Na2S2O3
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Answer 1

Explanation:

To Find

1. Oxidation number of S in H2SO3
2. Oxidation number of Na2S2O3

Solution :-

1)

Let the O.N. of S be x.

Then,

→ 1×2 + x -2×3 = 0

→ x - 6 + 2 = 0

→ x = +4

Hence,

The O.N. of S in H2SO3 is +4

2)

Let the O.N. of S be x.

Then,

→ 1×2 + 2x -2×3 = 0

→ 2x + 2 - 6 = 0

→ 2x = 4

→ x = +2

Hence,

The O.N. of S in Na2S2O3 is +2

Additional information :-

Oxidation number :-

• It's a hypothetical number calculated on the basis of certain rules, assuming all the compounds to be ionic.

Rules :-

1. O.N. of any element in its free state is 0
2. O.N. of Li, Na, K, Rb, Cs, Fr = +1
3. O.N. of Be, Mg, Ca, Sr, Ba, Ra = +2
4. O.N. of F, CL, Br, I = -1
5. O.N. of H is generally +1, but in metal hydrides it's -1
6. O.N. of Oxygen is generally -2 (oxide), But in peroxide it's -1 and in superoxide it's -½.
7. O.N. of any ion is equal to its charge.
8. Sum of O.N. of all the atoms of a molecule is zero.