IB Chemistry HL – Topics 5 & 6 MASTER Study Guide

These flashcards cover key concepts from the IB Chemistry HL lecture notes on Energetics and Kinetics, providing definitions and important concepts necessary for understanding thermochemistry and reaction rates.

Energy

The capacity to do work or transfer heat.

System

The part of the universe you study; the surroundings are everything else.

State function

A property that depends only on the initial and final states, not on the path taken.

Heat (q)

Energy transfer due to a temperature difference.

Work (w)

Energy transfer through a force acting over a distance.

First Law of Thermodynamics

Conservation of energy, expressed as ∆E = q + w.

Enthalpy (H)

A state function defined as H = E + PV.

Exothermic Reaction

A reaction that releases heat (∆H < 0).

Endothermic Reaction

A reaction that absorbs heat (∆H > 0).

Calorimetry

The science of measuring heat transfer.

Hess’s Law

The principle that the enthalpy change is independent of the pathway between the initial and final states.

Bond Enthalpy

The energy required to break one mole of a bond in the gas phase.

Lattice Enthalpy

Enthalpy change when forming 1 mole of ionic solid from gaseous ions.

Entropy (S)

A measure of the dispersal of energy and matter; also known as disorder.

Second Law of Thermodynamics

In any spontaneous process, the total entropy of the universe increases (∆S_universe > 0).

Gibbs Free Energy (∆G)

A function that helps predict spontaneity, given by ∆G = ∆H - T∆S.

Rate of Reaction

The change in concentration of reactants or products per unit time.

Collision Theory

A theory stating that molecules must collide to react, with sufficient energy and proper orientation.

Activation Energy (Ea)

The minimum energy that must be provided for a reaction to occur.

Arrhenius Equation

k = A e^(−Ea/RT), which shows the relationship between the rate constant and temperature.

Rate-Determining Step (RDS)

The slowest step in a reaction mechanism, which controls the overall reaction rate.