Question

Which of the following solutions will have the highest osmotic pressure ?

• A. 0.1 M KCl
• B. 0.1 M \(CaCl_2\)
• C. 0.1 M Glucose
• D. 0.1 M Urea

Hint:

Osmotic pressure is a colligative property given by \(\pi = iCRT\), where \(i\) is the van't Hoff factor (number of particles per formula unit).

Answer 1

The Correct Option is B

Concept:
Osmotic pressure is a colligative property given by \(\pi = iCRT\), where \(i\) is the van't Hoff factor (number of particles per formula unit). At the same molar concentration, the solute that gives the most particles has the highest osmotic pressure.

Step 1:
Find \(i\) for each: KCl gives 2 ions (i = 2), \(CaCl_2\) gives 3 ions (i = 3), glucose and urea are non-electrolytes (i = 1).

Step 2:
Effective particle concentration: \(CaCl_2\) gives \(0.1 \times 3 = 0.3\) M, KCl gives 0.2 M, glucose and urea give 0.1 M each.

Answer: Option (B) 0.1 M \(CaCl_2\) has the highest osmotic pressure.