Find the molality of a solution (containing nonvolatile solute) if its vapour pressure is 2% below the vapour pressure of pure water.

Explanation

To find the molality of a solution containing a non-volatile solute when its vapor pressure is 2% below that of pure water, we can follow these steps:

### Step 1: Understand the Problem
We know that the vapor pressure of the solution (Ps) is 2% less than that of pure water (P0). This means:
\[ Ps = P0 - 0.02P0 = 0.98P0 \]

### Step 2: Use the Relative Lowering of Vapor Pressure Formula
The formula for relative lowering of vapor pressure is given by:
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