How mich urea `("molar mass"=60 g mol^(-1))` must be dissolved in 50 g of water so that the vapour pressure at room temperature is reduced by 25% ? Also calculate the molality of the solution obtained.

Explanation

To solve the problem, we need to determine how much urea must be dissolved in 50 g of water to reduce the vapor pressure by 25%. We will also calculate the molality of the resulting solution.

### Step-by-Step Solution:

1. **Understand the Vapor Pressure Reduction**:
- Let the initial vapor pressure of pure water (P₀) be 1 atm.
- A reduction of 25% means the vapor pressure of the solution (Pₛ) will be:
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