CHM1046

What is the system in thermodynamics?

The part of the universe being studied.

What are the surroundings?

Everything outside the system.

What is the universe in thermodynamics?

The system + the surroundings.

What is a spontaneous process?

A process that occurs without outside intervention under a given set of conditions.

What is a nonspontaneous process?

A process that does not occur unless energy is continuously supplied.

Does spontaneous mean fast?

No, spontaneous only refers to whether a process can occur, not how fast.

What is enthalpy (ΔH)?

Heat flow at constant pressure.

What does ΔH < 0 indicate?

An exothermic process (releases heat).

What does ΔH > 0 indicate?

An endothermic process (absorbs heat).

What is entropy (ΔS)?

A measure of disorder or randomness.

When does entropy increase?

When disorder increases.

What is the Second Law of Thermodynamics?

For any spontaneous process, the entropy of the universe increases.

What is the formula for entropy of the universe?

ΔS_universe = ΔS_system + ΔS_surroundings

What is the Third Law of Thermodynamics?

A perfect crystal at 0 K has an entropy of 0.

What is absolute entropy (S°)?

The entropy of a substance at standard conditions.

What does a positive ΔS_universe mean?

The process is spontaneous.

What is Gibbs Free Energy (ΔG)?

Energy available to do work.

What is the Gibbs Free Energy equation?

ΔG = ΔH − TΔS

What does ΔG < 0 indicate?

A spontaneous process.

What does ΔG > 0 indicate?

A nonspontaneous process.

What does ΔG = 0 indicate?

The system is at equilibrium.

What is a solution?

A homogeneous mixture.

What is a solute?

The substance being dissolved.

What is a solvent?

The substance doing the dissolving.

What does miscible mean?

Two liquids that dissolve completely in each other.

What does immiscible mean?

Two liquids that do not dissolve in each other.

What does “like dissolves like” mean?

Polar dissolves polar; nonpolar dissolves nonpolar.

What is molarity (M)?

Moles of solute per liter of solution.

Formula for molarity?

M = moles solute / liters solution

What is molality (m)?

Moles of solute per kilogram of solvent.

Formula for molality?

m = moles solute / kg solvent

Which concentration unit is temperature dependent?

Molarity.

Which concentration unit is temperature independent?

Molality

What is percent by mass?

(Mass solute / mass solution) × 100

What is mole fraction (X)?

Moles of a component divided by total moles.

What are parts per million (ppm) used for?

Very dilute solutions.

Formula for ppm?

(Mass solute / mass solution) × 10⁶

What are colligative properties?

Properties that depend on the number of solute particles, not identity.

Name the four main colligative properties.

Properties that depend on the number of solute particles, not identity.

Name the four main colligative properties.

Vapor pressure lowering, boiling point elevation, freezing point depression, osmotic pressure.

What happens to vapor pressure when solute is added?

Vapor pressure decreases.

What is Raoult’s Law?

P_solution = X_solvent × P°_solvent

What is freezing point depression?

Solutions freeze at lower temperatures than pure solvents.

Formula for freezing point depression?

ΔT_f = iK_f m

What is boiling point elevation?

Solutions boil at higher temperatures than pure solvents.

Formula for boiling point elevation?

ΔT_b = iK_b m

What is osmotic pressure (π)?

Pressure needed to stop osmosis.

Formula for osmotic pressure?

π = iMRT

What is reaction rate?

Change in concentration over time.

What factors affect reaction rate?

Concentration, temperature, catalysts, surface area, physical state.

What is collision theory?

Molecules must collide with enough energy and proper orientation to react.

What is activation energy (Eₐ)?

Minimum energy required for a reaction to occur.

How does temperature affect reaction rate?

Higher temperature increases reaction rate.

What does a catalyst do?

Lowers activation energy without being consumed.

Difference between exothermic and endothermic reactions?

Exothermic releases heat; endothermic absorbs heat.

What is a rate law?

An equation relating reaction rate to reactant concentrations.

General form of a rate law?

Rate = k[A]^m[B]^n

What is k?

The rate constant.

What determines reaction order?

Exponents in the rate law.

What is an integrated rate law?

equation showing concentration as a function of time.

Integrated rate law for first-order reactions?

ln[A] = −kt + ln[A]₀