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WAEC Chemistry 2014 Paper

Question : 15

Total: 45

The oxidation number of sulphur in Fe₂(SO₄)₃ is

Solution:

Concept:

The sum of oxidation numbers of all atoms in a neutral compound is zero.

Explanation:

Let the oxidation number of sulphur be

x

\mathrm{Fe}_2(\mathrm{SO}_4)_3

, iron has an oxidation number of

+3

and oxygen has

-2

There are 2 iron atoms, 3 sulphur atoms, and 12 oxygen atoms.

Write the equation:

2(+3) + 3x + 12(-2) = 0

Simplify:

+6 + 3x - 24 = 0

3x - 18 = 0

3x = 18

x = +6

Answer:

The oxidation number of sulphur is

+6

Therefore, the correct option is D.

+6

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