What is the correct sequence of the increasing order of freezing point at one atmosphere of the following 0.01 M aqueous solution?
1. Urea, 2. Potassium chloride, 3. potassium sulphate, 4. Potassium phosphate.
Select the correct answer using the codes gives below

Options

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

Answer

To determine the correct sequence of the increasing order of freezing points of the given 0.01 M aqueous solutions of urea, potassium chloride, potassium sulfate, and potassium phosphate, we need to analyze the van 't Hoff factor (i) for each solute. The van 't Hoff factor indicates how many particles a solute dissociates into when dissolved in a solvent. The freezing point depression (ΔTf) is directly proportional to the concentration of solute particles, which means that a higher value of i will lead to a greater depression of the freezing point, resulting in a lower freezing point.

### Step-by-step Solution:

1. **Identify the van 't Hoff factor (i) for each solute:**
- **Urea (NH2CONH2)**: Urea does not dissociate in solution, so i = 1.
- **Potassium Chloride (KCl)**: KCl dissociates into K⁺ and Cl⁻, so i = 2.
- **Potassium Sulfate (K2SO4)**: K2SO4 dissociates into 2 K⁺ and SO4²⁻, so i = 3.
- **Potassium Phosphate (K3PO4)**: K3PO4 dissociates into 3 K⁺ and PO4³⁻, so i = 4.

2. **Calculate the effective concentration of solute particles (Cnet):**
- For each solute, Cnet = i × concentration.
- Urea: Cnet = 1 × 0.01 M = 0.01
- KCl: Cnet = 2 × 0.01 M = 0.02
- K2SO4: Cnet = 3 × 0.01 M = 0.03
- K3PO4: Cnet = 4 × 0.01 M = 0.04

3. **Determine the order of freezing point depression (ΔTf):**
- The greater the value of Cnet (or i), the lower the freezing point.
- Therefore, the order of freezing point depression is:
- Urea (i = 1) > KCl (i = 2) > K2SO4 (i = 3) > K3PO4 (i = 4)

4. **Establish the order of increasing freezing points:**
- Since the freezing point is inversely proportional to the van 't Hoff factor:
- The sequence of increasing order of freezing point is:
- K3PO4 < K2SO4 < KCl < Urea

### Final Answer:
The correct sequence of the increasing order of freezing points is:
**K3PO4 < K2SO4 < KCl < Urea**