What is the correct sequence of the increasing order of freezing points at one atmosphere of the following 1.0 M aqueous solution?
1. Urea, 2. Sodium chloride, 3. Sodium sulphate, 4. Sodium phosphate.
Select the correct answer using the codes given below

Options

A. 4, 3, 1, 2
B. 3, 4, 2, 1
C. 3 4, 1, 2
D. 4, 3, 2, 1

Answer

To determine the correct sequence of the increasing order of freezing points for the given 1.0 M aqueous solutions of urea, sodium chloride, sodium sulfate, and sodium phosphate, we need to consider the concept of freezing point depression, which is a colligative property. This property depends on the number of solute particles in solution, which is influenced by the dissociation of the solutes into ions.

### Step-by-Step Solution:

1. **Identify the Van't Hoff factor (i)**:
- **Urea (non-electrolyte)**: Urea does not dissociate in solution, so \( i = 1 \).
- **Sodium Chloride (NaCl)**: Sodium chloride dissociates into two ions: \( Na^+ \) and \( Cl^- \), so \( i = 2 \).
- **Sodium Sulfate (Na2SO4)**: Sodium sulfate dissociates into three ions: \( 2 Na^+ \) and \( SO4^{2-} \), so \( i = 3 \).
- **Sodium Phosphate (Na3PO4)**: Sodium phosphate dissociates into four ions: \( 3 Na^+ \) and \( PO4^{3-} \), so \( i = 4 \).

2. **Determine the order of freezing point depression**:
- The freezing point depression (\( \Delta T_f \)) is proportional to the Van't Hoff factor (\( i \)). The greater the \( i \), the lower the freezing point.
- Therefore, we can summarize the \( i \) values:
- Urea: \( i = 1 \)
- Sodium Chloride: \( i = 2 \)
- Sodium Sulfate: \( i = 3 \)
- Sodium Phosphate: \( i = 4 \)

3. **Rank the solutions based on their freezing points**:
- Since the freezing point decreases with increasing \( i \), we rank them from the lowest to the highest freezing point:
- Sodium Phosphate (i = 4) has the lowest freezing point.
- Sodium Sulfate (i = 3) has the next lowest freezing point.
- Sodium Chloride (i = 2) follows.
- Urea (i = 1) has the highest freezing point.

4. **Final Order**:
- Therefore, the correct sequence of the increasing order of freezing points is:
- Sodium Phosphate < Sodium Sulfate < Sodium Chloride < Urea
- In terms of the original question, this corresponds to the order: 4 (Sodium Phosphate), 3 (Sodium Sulfate), 2 (Sodium Chloride), 1 (Urea).

### Conclusion:
The correct answer is option 4: 4 (Sodium Phosphate) < 3 (Sodium Sulfate) < 2 (Sodium Chloride) < 1 (Urea).