List the following aqueous solutions in order of decreasing freez...

Question

List the following aqueous solutions in order of decreasing freezing point: 0.040 m glycerin (C3H8O3), 0.020 m KBr, 0.030 m phenol (C6H5OH).

Accepted Answer

Step 1: Understand that the freezing point of a solution is affected by the number of solute particles in the solution, which is described by the colligative property known as freezing point depression.. Step 2: Recall the formula for freezing point depression: $$ \Delta T_f = i \cdot K_f \cdot m $$, where $$ \Delta T_f  is $$the change in freezing point, $$ i  is $$the van't Hoff factor, $$ K_f  is $$the freezing point depression constant, and $$ m  is $$the molality of the solution.. Step 3: Determine the van't Hoff factor $$ i $$ for each solute: Glycerin (C3H8O3) is a non-electrolyte, so $$ i = 1 $$; KBr is an electrolyte that dissociates into K+ and Br-, so $$ i = 2 $$; Phenol (C6H5OH) is a weak electrolyte, but for simplicity, assume $$ i = 1 .. $$Step 4: Calculate the effective molality for each solution by multiplying the molality by the van't Hoff factor: Glycerin: $$ 0.040 	imes 1 = 0.040 $$, KBr: $$ 0.020 	imes 2 = 0.040 $$, Phenol: $$ 0.030 	imes 1 = 0.030 .. $$Step 5: Rank the solutions in order of decreasing freezing point. The solution with the lowest effective molality will have the highest freezing point. Therefore, the order is: Phenol (0.030 m), Glycerin (0.040 m), KBr (0.040 m).

List the following aqueous solutions in order of decreasing freezing point: 0.040 m glycerin (C3H8O3), 0.020 m KBr, 0.030 m phenol (C6H5OH).

Key Concepts

Freezing Point Depression

Van't Hoff Factor (i)

Molality (m)