Question

The solution which has the lowest freezing point is

• A. 0.2M K\(_2\)SO\(_4\)
• B. 0.2M KCl
• C. 0.2M NaNO\(_3\)
• D. 0.2M MgSO\(_4\)

Hint:

The more ions a solute dissociates into, the greater the freezing point depression.

Answer 1

The Correct Option is A

The freezing point depression is directly related to the number of particles in solution, as per the formula: \[ \Delta T_f = i \cdot K_f \cdot m \] Where: - \( \Delta T_f \) is the freezing point depression - \( i \) is the van 't Hoff factor (number of particles produced in solution) - \( K_f \) is the cryoscopic constant (depends on the solvent) - \( m \) is the molality of the solution The van 't Hoff factor \( i \) is highest for salts that dissociate into more ions. - K\(_2\)SO\(_4\) dissociates into 3 ions (K\(^+\), K\(^+\), SO\(_4^{2-}\)) - KCl dissociates into 2 ions (K\(^+\), Cl\(^-\)) - NaNO\(_3\) dissociates into 2 ions (Na\(^+\), NO\(_3^-\)) - MgSO\(_4\) dissociates into 2 ions (Mg\(^{2+}\), SO\(_4^{2-}\)) Thus, the solution with the lowest freezing point depression is the one with the highest number of ions, which is 0.2M K\(_2\)SO\(_4\).