Question

A solution consists of 10.3 g of the nonelectrolyte glucose, C6H12O6, dissolved in 250. g of ethanol. What is the new freezing point of the ethanol solution

Answer 1

-114.6°C is the new freezing point

Step-by-step explanation:

The addition of a solute to a pure solvent produce the decreasing in the freezing point (Freezing point depression, Colligative property). The equation to find the new freezing point of the mixture is:

ΔT = Kf*m*i

Where ΔT is the change in the freezing point,

Kf is the freezing point depression constant of the solvent = 1.99°C/m

m is molality of the solution (Moles of solute / kg solvent)

i is Van't Hoff factor = 1 for nonelectrolytes

Molality of the solution is:

Moles glucose -Molar mass: 180.156g/mol-

10.3g * (1mol / 180.156g) = 0.05717 moles

kg of solvent:

250g * (1kg / 1000g) = 0.250kg

Molality = 0.05717 moles / 0.250kg =

0.2287m

ΔT = 1.99°C/m*0.2287m*1

ΔT = 0.46°C

As the freezing point of ethanol is -114.1°C, the freezing point of te solution is:

-114.1°C - 0.46°C

= -114.6°C is the new freezing point