Colligative Properties & Tonicity Calculations Lecture 1

Questions and Answers

Which of the following is NOT a colligative property?

Boiling point elevation

Color change (correct)

Freezing point depression

Vapour pressure lowering

What are colligative properties dependent on?

The number of dissolved non-volatile solute species.

Osmotic pressure is of primary significance to pharmacists.

True

What is Raoult's law related to?

The vapour pressure of a solvent over a dilute solution. Signup and view all the answers

The vapour pressure, P1, of a solvent over a dilute solution is equal to the vapour pressure of the pure solvent multiplied by the __________ of solvent in the solution.

mole fraction Signup and view all the answers

What are colligative properties of solutions?

Physical properties dependent on the number of dissolved non-volatile solute species. Signup and view all the answers

What happens to the entropy of the solvent when a solute is dissolved?

Entropy increases. Signup and view all the answers

Which of the following are colligative properties? (Select all that apply)

Osmotic pressure Signup and view all the answers

Osmotic pressure is significant to pharmacists.

True Signup and view all the answers

What occurs when a solute is dissolved in a solvent?

The solvent molecules become more disordered, increasing entropy. Signup and view all the answers

According to Raoult’s law, P1 = X1______

𝜌𝜌1o Signup and view all the answers

Match the terms with their definitions:

Vapor pressure lowering = The decrease in vapor pressure when a non-volatile solute is added to a solvent. Boiling point elevation = The increase in boiling point due to the presence of a solute. Freezing point depression = The decrease in freezing point of a solvent with solute addition. Osmotic pressure = The pressure required to prevent the flow of solvent into a solution through a semipermeable membrane. Signup and view all the answers

Study Notes

Learning Outcomes

Ability to identify and discuss colligative properties of solutions.
Understanding of iso-osmoticity versus isotonicity.
Recognition of the importance of isotonicity in pharmaceutical preparations.
Skill to perform calculations related to tonicity in pharmaceuticals.

Colligative Properties

Defined as physical properties of solutions dependent on the number of dissolved non-volatile solute species.
Key types of colligative properties include:
- Vapour pressure lowering
- Boiling point elevation
- Freezing point depression
- Osmotic pressure
Osmotic pressure is particularly significant in pharmacy practices.

Vapour Pressure Lowering

Non-volatile solutes decrease the vapour pressure of a solvent.
Vapour pressure of the solution is lower than that of the pure solvent due to increased disorder (entropy).
Reduction in vapour pressure is proportional to the relative number of solute molecules in the solution.
Raoult’s law explains the relationship:
- Vapour pressure of a solvent over a dilute solution (P1) equals the pure solvent vapour pressure (𝜌𝜌1o) multiplied by the mole fraction of the solvent (X1).
- Representation: P1 = X1𝜌𝜌1o
Vapour pressure lowering can be quantified as:
- ΔP = X2 𝜌𝜌1o (where X2 is the mole fraction of solute).

Elevation of Boiling Point

The boiling point is defined as the temperature where the liquid's vapour pressure equals atmospheric pressure.
Elevation of boiling point occurs when a solute is added, requiring a higher temperature for the vapour pressure to equal the atmospheric pressure.

Importance of Entropy

Dissolving a solute increases the disorder of solvent molecules, leading to higher entropy (S).
Increase in entropy results in lower free energy (G), described by the equation ΔG = ΔH – TΔS.

Learning Outcomes

Ability to identify and discuss colligative properties of solutions.
Understanding of iso-osmoticity versus isotonicity.
Recognition of the importance of isotonicity in pharmaceutical preparations.
Skill to perform calculations related to tonicity in pharmaceuticals.

Colligative Properties

Defined as physical properties of solutions dependent on the number of dissolved non-volatile solute species.
Key types of colligative properties include:
- Vapour pressure lowering
- Boiling point elevation
- Freezing point depression
- Osmotic pressure
Osmotic pressure is particularly significant in pharmacy practices.

Vapour Pressure Lowering

Non-volatile solutes decrease the vapour pressure of a solvent.
Vapour pressure of the solution is lower than that of the pure solvent due to increased disorder (entropy).
Reduction in vapour pressure is proportional to the relative number of solute molecules in the solution.
Raoult’s law explains the relationship:
- Vapour pressure of a solvent over a dilute solution (P1) equals the pure solvent vapour pressure (𝜌𝜌1o) multiplied by the mole fraction of the solvent (X1).
- Representation: P1 = X1𝜌𝜌1o
Vapour pressure lowering can be quantified as:
- ΔP = X2 𝜌𝜌1o (where X2 is the mole fraction of solute).

Elevation of Boiling Point

The boiling point is defined as the temperature where the liquid's vapour pressure equals atmospheric pressure.
Elevation of boiling point occurs when a solute is added, requiring a higher temperature for the vapour pressure to equal the atmospheric pressure.

Importance of Entropy

Dissolving a solute increases the disorder of solvent molecules, leading to higher entropy (S).
Increase in entropy results in lower free energy (G), described by the equation ΔG = ΔH – TΔS.

Description

Explore the fascinating world of colligative properties and tonicity in this first lecture. Deepen your understanding of how these concepts apply in calculations and their significance in various scientific fields. Ideal for students looking to enhance their knowledge in chemistry and biology.