Question

Which of the following substances show the highest colligative properties?

• A. 0.1M BaCl$_2$
• B. 0.1M AgNO$_3$
• C. 0.1M urea
• D. 0.1M (NH$_4$)$_3$PO$_4$

Hint:

Colligative properties increase with the number of particles in solution. More dissociation leads to stronger effects.

Answer 1

The Correct Option is D

Step 1: Understanding Colligative Properties 
- Colligative properties depend on the number of particles in the solution rather than their nature. 
- The van't Hoff factor (\(i\)) represents the number of ions each molecule dissociates into. 
Step 2: Calculating the Number of Ions 
BaCl$_2$ dissociates into 3 ions: Ba$^{2+}$ and 2Cl$^-$. 
AgNO$_3$ dissociates into 2 ions: Ag$^+$ and NO$_3^-$. 
Urea does not dissociate, so \( i = 1 \).
(NH$_4$)$_3$PO$_4$ dissociates into 4 ions: 3 NH$_4^+$ and 1 PO$_4^{3-}$. 
Step 3: Identifying the Substance with the Highest Colligative Property 
The greater the number of ions, the higher the colligative properties. 
Since (NH$_4$)$_3$PO$_4$ produces 4 ions, it exhibits the highest colligative effect.
Thus, the correct answer is (D).