Mastering Chemical Equilibrium: Fundamentals and Properties

Reversible

Refers to chemical reactions that can proceed in both forward and reverse directions.

Chemical Equilibrium

A state in a closed system where the rate of the forward reaction equals the rate of the reverse reaction.

Dynamic Process

A process that is continuously changing; in equilibrium, reactants and products are present in constant concentrations.

Rate$_{forward}$

The speed at which reactants convert to products in a chemical reaction.

Rate$_{reverse}$

The speed at which products convert back to reactants in a chemical reaction.

Equilibrium Constant (K)

A numerical value that describes the ratio of concentrations of products to reactants at equilibrium.

Law of Mass Action

A principle that relates the concentrations of reactants and products to the rate of a chemical reaction.

$K_c$

The equilibrium constant expressed in terms of molar concentrations.

$K_p$

The equilibrium constant expressed in terms of partial pressures.

Stoichiometric Coefficient

Numbers in a balanced equation that represent the ratio of moles of each substance involved in the reaction.

Molar concentration

The number of moles of solute per liter of solution, expressed in moles per liter (M).

Reaction Quotient (Q)

A measure of the relative amounts of products and reactants at any point in a reaction, calculated in the same way as K.

$Q < K$

Indicates that the reaction will shift to the right to form more products.

$Q = K$

Indicates the system is at equilibrium, and no shift is required.

$Q > K$

Indicates that the reaction will shift to the left to form more reactants.

Hess's Law

A principle that allows for the calculation of the overall energy change of a reaction based on individual steps.

Temperature-dependent

Describes a property or constant that can change with temperature, such as the equilibrium constant.

Activities in Equilibrium Expressions

Refers to the concentrations of reactants and products used in equilibrium calculations; exclude solids and liquids.

Right Shift

Movement of equilibrium towards products in a chemical reaction, usually when $Q < K$.

Left Shift

Movement of equilibrium towards reactants in a chemical reaction, usually when $Q > K$.

Current Concentrations

The amounts of reactants and products present at a specific time, used to calculate $Q$.

Multi-step Equilibrium Calculation

Combining $K$ values of individual reactions to find the overall $K$ for a multi-step reaction.

Equilibrium Data Calculation

The process of calculating the equilibrium constant from known equilibrium concentrations of reactants and products.

Common Mistakes in Equilibrium

Errors often made in equilibrium calculations, including misunderstanding concentration relationships and notation.

P.O.R.

A mnemonic for remembering how to write equilibrium expressions: Products Over Reactants.

Constant Concentrations

Refers to the idea that the concentrations of reactants and products do not change at equilibrium.

Chemical Reaction Representation

Use of symbols and formulas to convey the chemical process and its products.