`12. g` of an impure sample of arsenious oxide was dissolved in water containing `7.5 g` of sodium bicarbonate and the resulting solution was diluted to `250 mL`. `25 mL` of this solution was completely oxidised by `22.4 mL` of a solution of iodine. `25 mL` of this iodine solution reacted with same volume of a solution containing `24.8 g` of sodium thiosulphate `(Na_(2)S_(2)O_(3).5H_(2)O)` in one litre. Calculate teh percentage of arsenious oxide in the sample ( Atomic mass of `As=74`)

Explanation

To solve the problem step by step, we will follow a systematic approach to calculate the percentage of arsenious oxide (As₂O₃) in the impure sample.

### Step 1: Write down the relevant reactions and determine n factors.

1. **For Sodium Thiosulfate (Na₂S₂O₃)**:
The reaction can be represented as:
\[
\text{S}_2\text{O}_3^{2-} + 2e^- \rightarrow \text{S}_4\text{O}_6^{2-}
...