Casio EA-200, EA200 Equipment, Equipment, T1 = K1 m, T2 = K2 m, Setting Up the Boiling Point Elevation Equipment, Setting Up the Freezing Point Depression Equipment

2-11-1

Dilute Solution Properties

English

Activity:tivity: SetupSetup

Equipment

This activity investigates boiling point elevation and freezing point depression of a dilute solution.

Theory

Dissolving a small amount of a substance (solute) in a theoretically pure liquid (solvent) to create a dilute solution causes the boiling point of the dilute solution to become greater than and the freezing point to become less than that of the solvent. This is because the proportion of solvent molecules is reduced by the amount of solute molecules mixed in, which lowers the vapor pressure of the solvent and elevates the boiling point. At the same time, it also reduces the proportion of solvent molecules that congeal, which suppresses the freezing point. These changes are determined by the amount of solute molecules, and the type of solute does not matter, as long as it is non-volatile. Consequently, both boiling point elevation and freezing point depression are proportional to the solute molality, as shown in the expressions below.

T1 = K1 m	T1(°C)	: Boiling Point Elevation of Solution
T2 = K2 m	T2(°C)	: Freezing Point Depression of Solution
T2 = K2 m	K1(°C kg/mol) : Molal Boiling Point Elevation Constant
	K1(°C kg/mol) : Molal Boiling Point Elevation Constant
	K2(°C kg/mol) : Molal Freezing Point Depression
		Constant
	m(mol/kg)	: Molality

1Solvent

2Solution

3Boiling Point Elevation

4Freezing Point Depression

T(°C) : Temperature

P(atm) : Vapor Pressure

t(s) : Time

Here, the proportion coefficient is determined by the solvent type. It is a constant that is not affected by the solute type. For example, the molal boiling point elevation constant for benzene is 2.53°C kg/mol, and the boiling point is 80.1°C. The molal freezing point depression constant is 5.12°C kg/mol, and the freezing point is 5.53°C.

When the solvent is pure water, the molal boiling point elevation constant is 0.515°C kg/mol, and the boiling point is 100°C. The molal freezing point depression constant is 1.853°C kg/mol, and the freezing point is 0°C.

Stand	Heater	Reflux Condenser	Desiccant
Auto Stirrer	Beaker	Round Bottom Flask (2)	Mixing Stick
Ice Water	Benzene	Naphthalene

Temperature Measurement Setup (EA-200, graphic scientific calculator, data communication cable, temperature probe)

Setting Up the Boiling Point Elevation Equipment

uPour the benzene solution into the flask, and secure it in place as shown in the illustration.

1Stand

2Heater

3Round Bottom Flask

4Reflux Condenser

5Desiccant

6Naphthalene-Benzene Solution

7Temperature Probe (CH1)

8EA-200

9Water Flow Direction

Setting Up the Freezing Point Depression Equipment

uPour the benzene solution into the flask, and secure it in place as shown in the illustration.

1Stand

2Auto Stirrer

3Beaker

4Round Bottom Flask

5Mixing Stick

6Ice Water

7Temperature Probe (CH1)

8EA-200

20020601