The vapour pressure of a pure liquid is 0.043 bar at a certain temperature. When a nonvolatile solute is dissolved into it, the vapour pressure of the solution is found to be 0.041 bar. What is the relative lowering of vapour pressure?

Answer

To find the relative lowering of vapor pressure, we can follow these steps:

### Step 1: Identify the given values
- Vapor pressure of the pure liquid (P₀) = 0.043 bar
- Vapor pressure of the solution (P) = 0.041 bar

### Step 2: Use the formula for relative lowering of vapor pressure
The formula for relative lowering of vapor pressure is given by:

\[ \text{Relative lowering of vapor pressure} = \frac{P₀ - P}{P₀} \]

### Step 3: Substitute the values into the formula
Substituting the given values into the formula:

\[ \text{Relative lowering of vapor pressure} = \frac{0.043 \, \text{bar} - 0.041 \, \text{bar}}{0.043 \, \text{bar}} \]

### Step 4: Calculate the difference in vapor pressures
Calculate the difference:

\[ 0.043 \, \text{bar} - 0.041 \, \text{bar} = 0.002 \, \text{bar} \]

### Step 5: Divide by the vapor pressure of the pure liquid
Now, divide the difference by the vapor pressure of the pure liquid:

\[ \text{Relative lowering of vapor pressure} = \frac{0.002 \, \text{bar}}{0.043 \, \text{bar}} \]

### Step 6: Perform the division
Calculating the division:

\[ \text{Relative lowering of vapor pressure} \approx 0.0465 \]

### Conclusion
The relative lowering of vapor pressure is approximately **0.0465**.

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