Calculate the molality of the solution of nonvolatile solute if it freezes at -0.36^ C . [ K _ f for solvent =1.86 ~K ~kg ~mol ⁻¹ ]

Step-by-step solution

Molality determination via freezing point depression The freezing point depression T_f = T_f^ - T_f = 0^ C - (-0.36^ C ) = 0.36 K , where T_f^ = 0^ C is the normal freezing point of water. Using the colligative property relation T_f = K_f m , where K_f = 1.86 K kg mol ⁻¹ for water, the molality is m = T_f K_f = 0.36 1.86 0.1935 mol kg ⁻¹ . Rounded to three significant figures, m = 0.193 mol kg ⁻¹ , which corresponds to option B .