WAEC SSCE - Chemistry - 2014 (Objective)

Question 1 Report

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

+2.

+4.

+6. Correct answer

Answer Details

In Fe₂(SO₄)₃, there are two iron (Fe) atoms and three sulfate (SO₄) ions. Each sulfate ion has a charge of -2, and the total negative charge of the three sulfate ions is -6. Since the compound as a whole is neutral, the total positive charge must be +6. To find the oxidation number of sulfur (S) in sulfate (SO₄) ion, we need to apply the following rule: the sum of the oxidation numbers of all atoms in a compound must be equal to the overall charge of the compound. In sulfate ion, oxygen (O) always has an oxidation number of -2, so the total oxidation number contributed by four oxygen atoms in SO₄ is -8. Therefore, the oxidation number of S in SO₄ can be calculated as follows: (-2 × 4) + (oxidation number of S) = -2 Simplifying the above equation, we get: -8 + (oxidation number of S) = -2 (oxidation number of S) = +6 So, the oxidation number of sulfur in Fe₂(SO₄)₃ is +6. Therefore, the correct option is +6.






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