Among 1% solutions of urea. Glucose and sucrose

Options

A. the vapour pressure and freezing point are the lowest for urea
B. the vapour pressure and boiling point are the lowest for urea
C. the depression in freezing point is the highest for urea
D. the elevation in boiling point is the highest for urea

Answer

To solve the question regarding the 1% solutions of urea, glucose, and sucrose, we will follow these steps:

### Step 1: Understanding the 1% Solution
A 1% solution means that there is 1 gram of solute (urea, glucose, or sucrose) dissolved in 100 mL of solvent (water).

### Step 2: Determine the Molar Mass of Each Compound
- **Urea (NH₂CONH₂)**: Molar mass = 60 g/mol
- **Glucose (C₆H₁₂O₆)**: Molar mass = 180 g/mol
- **Sucrose (C₁₂H₂₂O₁₁)**: Molar mass = 342 g/mol

### Step 3: Calculate Molarity of Each Solution
Molarity (M) is calculated using the formula:
\[ \text{Molarity} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)} \times \text{volume (L)}} \]
For each solution:
- **Urea**:
\[ M = \frac{1 \text{ g}}{60 \text{ g/mol} \times 0.1 \text{ L}} = \frac{1}{6} \text{ mol/L} \approx 0.167 \text{ mol/L} \]
- **Glucose**:
\[ M = \frac{1 \text{ g}}{180 \text{ g/mol} \times 0.1 \text{ L}} = \frac{1}{18} \text{ mol/L} \approx 0.056 \text{ mol/L} \]
- **Sucrose**:
\[ M = \frac{1 \text{ g}}{342 \text{ g/mol} \times 0.1 \text{ L}} = \frac{1}{34.2} \text{ mol/L} \approx 0.029 \text{ mol/L} \]

### Step 4: Compare Molarities
From the calculations:
- Urea has the highest molarity (0.167 mol/L)
- Glucose has the middle molarity (0.056 mol/L)
- Sucrose has the lowest molarity (0.029 mol/L)

### Step 5: Analyze Vapor Pressure and Freezing Point
- **Vapor Pressure**: Vapor pressure is inversely proportional to the concentration of solute. Therefore, the solution with the highest concentration (urea) will have the lowest vapor pressure.
- **Freezing Point Depression**: The freezing point depression is directly proportional to the concentration of solute. Thus, urea will have the greatest freezing point depression.

### Step 6: Analyze Boiling Point Elevation
- **Boiling Point Elevation**: Similar to freezing point depression, boiling point elevation is also directly proportional to the concentration. Urea will thus have the highest boiling point elevation.

### Conclusion
Based on the above analysis:
- Urea has the lowest vapor pressure, the highest freezing point depression, and the highest boiling point elevation.
- Glucose has a moderate effect, while sucrose has the least effect.

### Final Answer
The correct statements regarding the 1% solutions of urea, glucose, and sucrose are:
- Vapor pressure is lowest for urea.
- Freezing point is lowest for urea.
- Depression in freezing point is highest for urea.
- Elevation in boiling point is highest for urea.