The density of 3M solution of sodium thiosulphate `(Na_(2)S_(2)O_(3))` is `1.25` calculate
(i) amount of sodium thiosulphate
(ii) mole fraction of sodium thiosulphate
(iii) molality of `Na^(+)` and `S_(2)O_(3)^(2-)` ions

Explanation

To solve the problem, we will follow these steps:

### Step 1: Calculate the mass of the solution
Given that the density of the solution is 1.25 g/cm³ and we are considering 1 liter (1000 cm³) of the solution:

\[ \text{Mass of solution} = \text{Density} \times \text{Volume} = 1.25 \, \text{g/cm}^3 \times 1000 \, \text{cm}^3 = 1250 \, \text{g} \]
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