What mass of a solute (M = 345) is needed to decrease the vapour pressure of 100 g of `H_2O` at `25^@C` by 1 mmHg? Vapour pressure of water at `25^@C` is 23.756 mm.

Explanation

To solve the problem of determining the mass of a solute needed to decrease the vapor pressure of 100 g of water at 25°C by 1 mmHg, we can use Raoult's Law. Here’s a step-by-step solution:

### Step 1: Understand Raoult's Law
Raoult's Law states that the vapor pressure of a solvent is directly proportional to the mole fraction of the solvent in the solution. The formula is given by:

\[ P_{solution} = X_{solvent} \cdot P^0_{solvent} \]
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