For which of the following solutes the van't Hoff factor is not greater than one ?

Options

A. `NaNO_3`
B. `BaCl_2`
C. `K_4[Fe(CN)_6]`
D. `NH_2CONH_2`

Explanation

To determine which of the following solutes has a van't Hoff factor (i) that is not greater than one, we need to analyze each option based on whether they are electrolytes or non-electrolytes.

### Step-by-Step Solution:

1. **Understand the van't Hoff factor (i)**:
- The van't Hoff factor (i) represents the number of particles into which a solute dissociates in solution.
- For electrolytes (substances that dissociate into ions), the value of i is greater than 1.
- For non-electrolytes (substances that do not dissociate into ions), the value of i is equal to 1.

2. **Analyze each option**:
- **Option 1: NaNO3**:
- Sodium nitrate (NaNO3) is an electrolyte. It dissociates into Na⁺ and NO3⁻ ions in solution.
- Therefore, i = 2 (1 Na⁺ + 1 NO3⁻).

- **Option 2: BaCl2**:
- Barium chloride (BaCl2) is also an electrolyte. It dissociates into Ba²⁺ and 2 Cl⁻ ions.
- Therefore, i = 3 (1 Ba²⁺ + 2 Cl⁻).

- **Option 3: K4[Fe(CN)6]**:
- Potassium ferrocyanide (K4[Fe(CN)6]) is an electrolyte. It dissociates into 4 K⁺ and 1 [Fe(CN)6]⁴⁻ ion.
- Therefore, i = 5 (4 K⁺ + 1 [Fe(CN)6]⁴⁻).

- **Option 4: NH2CONH2 (Urea)**:
- Urea (NH2CONH2) is a non-electrolyte. It does not dissociate into ions in solution.
- Therefore, i = 1.

3. **Conclusion**:
- Among the four options, the only solute for which the van't Hoff factor is not greater than one is **NH2CONH2 (Urea)**, as its value of i is equal to 1.

### Final Answer:
The solute for which the van't Hoff factor is not greater than one is **NH2CONH2 (Urea)**.