The osmotic pressure of a solution increases if

Options

A. Temperature is lowered
B. Volume is increased
C. Number of solute molecules is increased
D. None of these

Explanation

To determine how the osmotic pressure of a solution increases, we can analyze the relationship between osmotic pressure and various factors. The osmotic pressure (π) of a solution is given by the formula:

\[ \pi = iCRT \]

Where:
- \( \pi \) = osmotic pressure
- \( i \) = van 't Hoff factor (number of particles the solute dissociates into)
- \( C \) = concentration of the solution (moles of solute per liter of solution)
- \( R \) = universal gas constant
- \( T \) = absolute temperature (in Kelvin)

### Step-by-Step Solution:

1. **Understanding the Formula**:
- The osmotic pressure depends on the concentration of the solute, the temperature, and the number of particles the solute dissociates into (van 't Hoff factor).

2. **Analyzing Each Factor**:
- **Concentration (C)**: If the concentration of the solute increases, the osmotic pressure will also increase. This is because there are more solute particles in the same volume of solution.
- **Temperature (T)**: If the temperature increases, the kinetic energy of the particles increases, which leads to an increase in osmotic pressure. Thus, osmotic pressure is directly proportional to temperature.
- **Van 't Hoff Factor (i)**: If the solute dissociates into more particles (higher \( i \)), the osmotic pressure will also increase. For example, NaCl dissociates into two ions (Na⁺ and Cl⁻), thus increasing the effective concentration of particles.

3. **Conclusion**:
- The osmotic pressure of a solution increases if:
- The concentration of solute molecules is increased.
- The temperature of the solution is increased.
- The number of solute particles (due to dissociation) is increased.

### Final Answer:
The osmotic pressure of a solution increases if the number of solute molecules is increased.