Colligative Properties Flashcards

Questions and Answers

What is the definition of a colligative property?

Properties that depend on the concentration of solute particles, but not on their identity.

In calculations involving colligative properties, concentration is provided by what?

Molality

What is the equation for molality?

M = moles of solute/kg of solvent

What are the 4 colligative properties?

Vapor Point Reduction, Boiling Point Elevation, Freezing Point Depression, Osmotic Pressure Signup and view all the answers

What happens during vapor pressure reduction?

A nonvolatile solute is added to a pure solvent, preventing solvent molecules from leaving and reentering the liquid. Signup and view all the answers

Few what exist above the liquid causing vapor pressure reduction?

Gas molecules Signup and view all the answers

Boiling point is the temperature at which vapor pressure above a liquid equalizes with what?

Atmospheric Pressure Signup and view all the answers

Because solute addition reduces vapor pressure, a what temperature is necessary to get the vapor pressure up to atmospheric pressure?

Higher Signup and view all the answers

The amount by which the boiling point is raised by solute addition is called what?

Boiling Point Elevation Signup and view all the answers

The BPE is the difference between the boiling point of the what and that of the solution.

Pure solvent Signup and view all the answers

The BPE is directly proportional to what?

Molality Signup and view all the answers

What is the equation for BPE?

Tb = Kb x m Signup and view all the answers

What is Kb?

Molal boiling point constant Signup and view all the answers

The ability of a dissolved solute to lower the freezing point of its solution is known as what?

Freezing Point Depression Signup and view all the answers

The decrease in the freezing point is directly proportional to what?

Molality of the solution Signup and view all the answers

What is the equation for FPD?

Tf = Kf x m Signup and view all the answers

What is osmosis?

Net flow of solvent molecules from the less concentrated to the more concentrated Signup and view all the answers

What does it mean to be semipermeable?

Allow certain particles to pass through Signup and view all the answers

Two solutions with identical osmotic pressure are said to be what?

Isotonic Signup and view all the answers

One solution has a lower osmotic pressure than another; it is said to be?

Hypotonic Signup and view all the answers

One solution has a higher osmotic pressure than another; it is said to be?

Hypertonic Signup and view all the answers

Study Notes

Colligative Properties Overview

Colligative properties depend on solute particle concentration rather than their identity.
Key properties include vapor pressure reduction, boiling point elevation, freezing point depression, and osmotic pressure.

Concentration Measurement

Molality (m) is the preferred measure of concentration for colligative property calculations.
The formula for molality is moles of solute per kilogram of solvent.

Vapor Pressure Reduction

Adding a nonvolatile solute to a pure solvent decreases the vapor pressure by occupying surface space, limiting solvent evaporation.
The presence of gas molecules above the liquid is necessary for vapor pressure.

Boiling Point Elevation

The boiling point is reached when the vapor pressure above a liquid equals atmospheric pressure.
Solute addition results in a higher boiling point necessary to achieve atmospheric pressure.
The difference in boiling point due to solute presence is termed boiling point elevation (BPE).
BPE is directly proportional to the solution's molality.

Equations for Boiling Point Elevation

The equation representing boiling point elevation is Tb = Kb x m, where Kb is the molal boiling point constant.

Freezing Point Depression

The ability of a solute to lower a solution's freezing point is known as freezing point depression (FPD).
FPD is directly proportional to the solution's molality.
The equation for freezing point depression is Tf = Kf x m, where Kf is the molal freezing point constant.

Osmosis

Osmosis refers to the net movement of solvent molecules from a less concentrated solution to a more concentrated one.
Semipermeable membranes only allow certain particles to pass through.

Types of Solutions Based on Osmotic Pressure

Solutions with identical osmotic pressure are classified as isotonic.
A solution with lower osmotic pressure is termed hypotonic.
A solution with higher osmotic pressure is referred to as hypertonic.

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