What is the Van't Hoff factor for sodium phosphate ?

Options

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

Answer

To determine the Van't Hoff factor (i) for sodium phosphate (Na₃PO₄), we will follow these steps:

### Step 1: Understand the Dissociation of Sodium Phosphate
Sodium phosphate dissociates in solution into its constituent ions. The dissociation reaction can be written as:
\[ \text{Na}_3\text{PO}_4 \rightarrow 3\text{Na}^+ + \text{PO}_4^{3-} \]

### Step 2: Count the Total Number of Ions Produced
From the dissociation equation, we can see that one formula unit of sodium phosphate produces:
- 3 sodium ions (Na⁺)
- 1 phosphate ion (PO₄³⁻)

Thus, the total number of particles (ions) produced from one formula unit of sodium phosphate is:
\[ 3 + 1 = 4 \]

### Step 3: Define the Van't Hoff Factor
The Van't Hoff factor (i) is defined as the number of particles into which a solute dissociates in solution. For sodium phosphate, since it dissociates into 4 ions, we can conclude:
\[ i = 4 \]

### Step 4: Conclusion
Therefore, the Van't Hoff factor for sodium phosphate (Na₃PO₄) is:
\[ \boxed{4} \]

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