How many of the following compounds will decolourize the colour of acidified ` KMnO_(4)`?
`{:(H_(2)S,FeSO_(4),NaNO_(2)),(Na_(2)SO_(3),PbS,Na_(2)S),(NaNO_(3),Na_(2)SO_(4),CO_(2)),(SO_(3),P_(2)O_(5),):}`

Explanation

To determine how many of the given compounds will decolorize acidified KMnO4, we need to analyze the oxidation states of the elements in each compound and see if they can be oxidized further. KMnO4 is a strong oxidizing agent, and it decolorizes when it is reduced from Mn(VII) to Mn(II).

Let's analyze each compound step by step:

1. **H₂S (Hydrogen sulfide)**:
- Sulfur in H₂S has an oxidation state of -2.
- It can be oxidized to higher oxidation states (up to +6).
- Therefore, H₂S can decolorize KMnO4.

2. **FeSO₄ (Iron(II) sulfate)**:
- Iron in FeSO₄ has an oxidation state of +2.
- It can be oxidized to +3.
- Thus, FeSO₄ can also decolorize KMnO4.

3. **NaNO₂ (Sodium nitrite)**:
- Nitrogen in NaNO₂ has an oxidation state of +3.
- It can be oxidized to +5 (in NaNO₃).
- Therefore, NaNO₂ can decolorize KMnO4.

4. **Na₂SO₃ (Sodium sulfite)**:
- Sulfur in Na₂SO₃ has an oxidation state of +4.
- It can be oxidized to +6 (in Na₂SO₄).
- Thus, Na₂SO₃ can decolorize KMnO4.

5. **PbS (Lead sulfide)**:
- Sulfur in PbS has an oxidation state of -2.
- It can be oxidized to +6.
- Therefore, PbS can decolorize KMnO4.

6. **Na₂S (Sodium sulfide)**:
- Sulfur in Na₂S has an oxidation state of -2.
- It can be oxidized to +6.
- Thus, Na₂S can decolorize KMnO4.

7. **NaNO₃ (Sodium nitrate)**:
- Nitrogen in NaNO₃ has an oxidation state of +5.
- This is the highest oxidation state for nitrogen; it cannot be oxidized further.
- Therefore, NaNO₃ will not decolorize KMnO4.

8. **Na₂SO₄ (Sodium sulfate)**:
- Sulfur in Na₂SO₄ has an oxidation state of +6.
- This is the highest oxidation state for sulfur; it cannot be oxidized further.
- Therefore, Na₂SO₄ will not decolorize KMnO4.

9. **CO₂ (Carbon dioxide)**:
- Carbon in CO₂ has an oxidation state of +4.
- This is the highest oxidation state for carbon; it cannot be oxidized further.
- Therefore, CO₂ will not decolorize KMnO4.

10. **SO₃ (Sulfur trioxide)**:
- Sulfur in SO₃ has an oxidation state of +6.
- This is the highest oxidation state for sulfur; it cannot be oxidized further.
- Therefore, SO₃ will not decolorize KMnO4.

11. **P₂O₅ (Phosphorus pentoxide)**:
- Phosphorus in P₂O₅ has an oxidation state of +5.
- This is the highest oxidation state for phosphorus; it cannot be oxidized further.
- Therefore, P₂O₅ will not decolorize KMnO4.

**Summary of Compounds that Decolorize KMnO4**:
- H₂S
- FeSO₄
- NaNO₂
- Na₂SO₃
- PbS
- Na₂S

**Total Compounds that Decolorize KMnO4**: 6