Question

1.2\% NaCl solution is isotonic to 7.2\% glucose solution. Calculate the van't Hoff factor for NaCl solution.

Hint:

For isotonic solutions, osmotic pressure equations can be equated to determine the van't Hoff factor.

Answer 1

Step 1: The van't Hoff factor (\( i \)) is determined using: \[ \pi = i M R T \] Since the solutions are isotonic, their osmotic pressures are equal: \[ i \times M_{\text{NaCl}} = M_{\text{glucose}} \] Step 2: Given: \[ M_{\text{NaCl}} = \frac{1.2}{58.5} = 0.0205 \text{ mol/L} \] \[ M_{\text{glucose}} = \frac{7.2}{180} = 0.04 \text{ mol/L} \] Step 3: Solve for \( i \): \[ i = \frac{M_{\text{glucose}}}{M_{\text{NaCl}}} = \frac{0.04}{0.0205} = 1.95 \] Thus, the van't Hoff factor for NaCl is 1.95.