Chemical Equilibrium Practice Flashcards

A set of vocabulary flashcards covering chemical equilibrium, reaction rates, energy changes, Le Chatelier's Principle, and environmental impacts like ocean acidification.

Exothermic Reaction

A chemical reaction that releases energy as heat to the surroundings, represented by a negative enthalpy change ($\Delta H = -ve$).

Endothermic Reaction

A chemical reaction that absorbs energy from the surroundings, represented by a positive enthalpy change ($\Delta H = +ve$).

Enthalpy (H)

The energy content of a system held at constant pressure.

Enthalpy Change ($\Delta H$)

The energy exchange between a chemical reaction and its surroundings at constant pressure, calculated as $H_{\text{products}} - H_{\text{reactants}}$.

Rate of Reaction

The speed at which a reactant is used up or a product forms, defined as $\frac{\text{Change in amount of reactants or products}}{\text{Time}}$.

Collision Theory

States that for a reaction to occur, reacting particles must collide in the correct orientation and with sufficient energy to overcome the activation energy barrier.

Activation Energy ($E_a$)

The minimum amount of energy molecules must have in order for the reaction to take place.

Maxwell-Boltzmann Distribution

A distribution showing that at a given temperature ($T$), particles in a system do not all possess the same amount of energy.

Catalyst

A substance that speeds up a chemical reaction by providing an alternative pathway with a lower activation energy ($E_a$) without being used up.

Irreversible Reactions

Chemical reactions where the products made cannot readily be changed back into their reactants.

Reversible Reactions

Reactions that can go in either direction, where products can react together to reform the original reactants; they typically have low $E_a$ for both directions.

Closed System

A system in which none of the reactants or products escape from the reaction mixture, which is a requirement for reaching equilibrium.

Dynamic Equilibrium

A state reached when the forward and reverse reactions occur at the same rate, resulting in constant concentrations of reactants and products.

Equilibrium Constant ($K$)

A value for an equilibrium reaction at constant temperature expressed as $K = \frac{[C]^p [D]^q}{[A]^m [B]^n}$ where indices are the stoichiometric coefficients.

Homogeneous Equilibria

An equilibrium where all reactants and products are in the same phase, such as all gases or all liquids.

Heterogeneous Equilibria

An equilibrium where reactants and products are present in more than one physical state; pure solids $(s)$ and liquids $(l)$ are omitted from the $K$ expression.

Partial Pressure

The pressure exerted by any one individual gas in a mixture of gases.

Saturated Solution

A solution where the rate of dissolving equals the rate of crystallization, resulting in the maximum solute concentration.

Le Chatelier’s Principle

States that if a system at equilibrium is disturbed by a change in conditions, the system will readjust to establish a new equilibrium that partially counteracts the imposed change.

Ocean Acidification

The process where falling ocean $\text{pH}$ and falling $[CO_3^{2-}]$ occur due to increased atmospheric $CO_2$ dissolving in the ocean.

Decalcification

A process in which more $CaCO_3(s)$ dissolves because decreased carbonate ion concentrations shift equilibrium to the right, impacting calcifying species.

Kyoto Protocol

A 1997 United Nations treaty aimed at reducing greenhouse gas emissions worldwide to combat global warming.