Find the amound of iron pyrites `(FeS_2)` which is sufficient to produce enough `SO_2` on roasting (heating in excess of `O_2`) such that is `(SO_2)` completely decolourise a 1 L solution of `KMnO_4` containing 15.8 g `L^(-1)` of it. The equation are
`FeS_2+O_2toFe_2O_3+SO_2`
`KMnO_4+SO_2toMnSO_4+H_2SO_4+KHSO_4`

Explanation

To solve the problem, we need to find the amount of iron pyrites (FeS₂) required to produce enough SO₂ to completely decolorize a 1 L solution of KMnO₄ containing 15.8 g/L. We will follow these steps:

### Step 1: Calculate the total amount of KMnO₄ in the solution
Given that the concentration of KMnO₄ is 15.8 g/L, for 1 L of solution:
- Mass of KMnO₄ = 15.8 g

### Step 2: Calculate the number of equivalents of KMnO₄
The molecular weight of KMnO₄ is approximately 158 g/mol. The valency factor (n) for KMnO₄ in acidic medium is 5 (as it reduces from Mn⁷⁺ to Mn²⁺).
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