A 10 g samle of only CuS and `Cu_(2)S` was treated with 100 ml of `1.25 M K_(2) Cr_(2) O_(7) ` . The Products obtained were `Cr^(3+) , Cu^(2+) " and " SO_(2) `. The excess oxidant was reacted with 50 ml of `Fe^(2+)` Solution : 25 ml of the same `Fe^(2+)` solution required `0.875 M KMnO_(4)` under acidic condition , the volume of `KMnO_(4)` used was 20 ml . Find the % of CuS and `Cu_(2)S` in the sample .

Explanation

To solve the problem step by step, we will go through the following calculations:

### Step 1: Calculate the equivalence of potassium dichromate (K₂Cr₂O₇)

1. **Given Data:**
- Molarity (M) of K₂Cr₂O₇ = 1.25 M
- Volume (V) of K₂Cr₂O₇ = 100 mL = 0.1 L
- N-factor for K₂Cr₂O₇ = 6 (since it can accept 6 electrons)
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