**The Van't Hoff Factor: An Expression of Solute Dissociation or Association**

The Van't Hoff factor is a concept used to express the extent to which a solute is dissociated or associated in a solution. It is denoted by the symbol "i" and is defined as the ratio between the actual number of particles formed when a solute is dissolved in a solvent and the number of formula units or molecules initially present in the solute.

**Substantiating the Statement:**

The Van't Hoff factor is an essential concept in understanding the behavior of solutes in solution. It helps us determine whether a solute dissociates or associates when dissolved and how this impacts various solution properties, such as boiling point elevation, freezing point depression, and osmotic pressure.

**Explanation in Detail:**

1. **Definition of the Van't Hoff Factor:**
The Van't Hoff factor (i) is calculated by dividing the number of particles formed in a solution by the number of formula units or molecules initially present in the solute. It is represented by the equation: i = (actual number of particles in solution) / (number of formula units or molecules initially present).

2. **Dissociation and Association:**
When a solute dissociates in a solvent, it breaks down into smaller particles, such as ions or molecules. For example, when table salt (NaCl) dissolves in water, it dissociates into sodium ions (Na+) and chloride ions (Cl-). On the other hand, association occurs when smaller particles combine to form larger ones. An example is acetic acid (CH3COOH), which associates in benzene to form dimers (CH3COOH)2.

3. **Van't Hoff Factor for Dissociation:**
For solutes that dissociate, the Van't Hoff factor is greater than 1. This is because the actual number of particles in the solution is higher than the number of formula units or molecules initially present. For example, when NaCl dissolves in water, it dissociates into one Na+ ion and one Cl- ion. Therefore, the Van't Hoff factor for NaCl in water is 2.

4. **Van't Hoff Factor for Association:**
For solutes that associate, the Van't Hoff factor is less than 1. This is because the actual number of particles in the solution is lower than the number of formula units or molecules initially present. For example, when acetic acid associates in benzene to form dimers, the Van't Hoff factor for acetic acid in benzene is 0.5.

5. **Application of the Van't Hoff Factor:**
The Van't Hoff factor is crucial in calculating colligative properties of solutions, which depend on the number of solute particles rather than their chemical identity. For example, when a solute dissociates in water, it increases the concentration of particles and results in a higher boiling point and lower freezing point compared to pure solvent. The Van't Hoff factor allows us to quantify these changes accurately.

In conclusion, the Van't Hoff factor is an expression of the extent to which a solute dissociates or associates in a solution. It is calculated by comparing the actual number of particles formed in the solution to the number of formula units or molecules initially present. Understanding the Van't Hoff factor helps us predict the behavior of solutes in solution and accurately calculate various solution properties.