Oxidation questions?

28.
The 1st option: H₂SO₃ is neither oxidizing agent nor reducing agent because the oxidation number of S is unchanged (+4).
The 2nd option: H₂SO₃ is neither oxidizing agent nor reducing agent because the oxidation number of S is unchanged (+4).
The 3rd option: H₂SO₃ is acting as a reducing agent because it is oxidized as the oxidation number of S increases from +4 to +6.
The 4th option: H₂SO₃ is acting as an oxidizing agent because it is reduced as the oxidation number of S in H₂SO₃ decreases from +4 to 0.

The answer: H₂SO₃ + 2H₂S → 3H₂O + 3S
(The 4th option)

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29.
The oxidation number of Cl in NaCl is -1, and in HCl is also -1. There is no change in oxidation number of Cl. 

The answer: No change in oxidation number

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30.
[1]: Cl⁻ → (1/2)Cl₂ + e⁻
[2]: MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O

To cancel the e⁻ on each side, [1]×5 + [2]. The overall equation is:
MnO₄⁻ + 5Cl⁻ + 8H⁺ → Mn²⁺ + (5/2)Cl₂ + 4H₂O
1 mol of MnO₄⁻ ions reacts with 5 moles of Cl⁻ ions.

The 1st option is true.
The 2nd option is false.
The 3rd and 4th options are false because Cl₂ is a product.

The answer: 1 mol of manganate(VII) ions reacts with 5 moles of chloride ions.

H2SO3 + H2S --> 3 H2O + 3 S

No change in oxidation number

1 mole of manganese(VII) reacts with 5 mol of Cl- ions