# Colligative Properties - PowerPoint PPT Presentation

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Colligative Properties. Vocabulary. Hypotonic – a cell that is placed in a solution and bursts. Raoult’s Law – states that the magnitude of vapor pressure reduction is proportional to the solution’s concentration. Isotonic – a solution where osmosis does not occur

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Colligative Properties

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## Colligative Properties

### Vocabulary

• Hypotonic – a cell that is placed in a solution and bursts.

• Raoult’s Law – states that the magnitude of vapor pressure reduction is proportional to the solution’s concentration.

• Isotonic – a solution where osmosis does not occur

• Freezing Point - the temperature at which vapor pressure of solid and liquid phase are the same

### Vocabulary

• Nonvolatile – a substance that will not become a gas under existing conditions

• Hypertonic – a cell that is placed in a solution and shrinks

• Osmosis – the net flow of molecules from less concentrated to more concentration solutions

• Boiling Point – the temperature at which vapor pressure of a liquid is equal to the eternal pressure on its surface

### Boiling Point Elevation

• Boiling Point Elevation – the boiling point of a liquid will be higher when another compound is added

• ΔT = Kb • m • i

• ΔT = change in temperature

• Kb = boiling point constant for the solvent

• m = molality (mol of solute ÷ kg of solvent)

• i = number of ions in solute

### Example #1

• What is the boiling point elevation for a solution containing 125g of ethylene glycol (C2H6O2) in 1200g of water? Kb for water = 0.52 C/m

• Convert 125 g of C2H6O2 to moles.

2. Convert 1200 g of water to kg.

3. Solve for m

4. Plug into the formula ΔT = Kb • m • i

### Example #2

• What is the boiling point elevation for a solution containing 125g of salt in 600g of water? Kb for water= 0.52 C/m

• Convert 125 g of NaClto moles.

2. Convert 600 g of water to kg.

3. Solve for m

3. Plug into the formula ΔT = Kb • m • i

### Freezing Point Depression

• Freezing Point Depression - the freezing point of a liquid will be lower when another compound is added

• ΔT = Kf • m • i

• ΔT = change in temperature

• Kf = constant for that particular solvent

• m = molality (mol of solute ÷ kg of solvent)

• i = number of ions in solute

### Example #1

• What is the freezing point depression when 85.3g of oxygen is dissolved in 1500g of water? Kf for water = 1.86 C/m

• Convert 85.3 g of oxygen to moles.

2. Convert 1500 g of water to kg.

3. Solve for m

4. Plug into the formula ΔT = Kf• m • i

### Example #2

• What is the freezing point depression of a solution prepared by dissolving 11.3 g of Ca(NO3)2 in 115 g of water? Kf for water= 1.86 °C/m.

• Convert 11.3 g of Ca(NO3)2 to moles.

• Convert 115 g of water to kg.

3. Solve for m

4. Plug into the formula ΔT = Kf• m • i