The vapour pressure of ethyl alcohol at `25^@C` is 59.2 torr. The vapour pressure of a solution of non-volatile solute urea, `NH_2CONH_2` in ethyl alcohol is 51.3 torr. What is the molality of solution ?

Explanation

To find the molality of the solution, we can use the concept of relative lowering of vapor pressure. Here’s a step-by-step solution:

### Step 1: Understand the Given Data
- Vapor pressure of pure ethyl alcohol (P₀) = 59.2 torr
- Vapor pressure of the solution (P₁) = 51.3 torr

### Step 2: Calculate the Relative Lowering of Vapor Pressure
The relative lowering of vapor pressure can be calculated using the formula:
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