Question

Why are equimolar solutions of sodium chloride and glucose not isotonic?

Hint:

The van 't Hoff factor (\( i \)) plays a crucial role in determining osmotic pressure. For ionic compounds like NaCl, \( i \) is greater than 1 due to dissociation, whereas for non-electrolytes like glucose, \( i = 1 \).

Answer 1

Sodium chloride undergoes dissociation (\( i = 2 \)) in water, while glucose does not (\( i = 1 \)). The osmotic pressure is given by: \[ \pi = i C R T \] For NaCl, \( i = 2 \), and for glucose, \( i = 1 \). Therefore, equimolar solutions of NaCl and glucose do not have the same osmotic pressure and are not isotonic.