General Chemical Equilibrium

This set of vocabulary flashcards covers the fundamental concepts, constants, and principles of chemical equilibrium including constant calculations, reaction quotients, and Le Châtelier’s Principle.

Chemical equilibrium

The state reached by a reaction mixture when the rates of the forward and reverse reactions have become equal, causing the concentration of all reactants and products to remain constant over time.

$$K_c$$

The equilibrium constant expressed in terms of molar concentrations, calculated by multiplying product concentrations and dividing by reactant concentrations, each raised to the power of its stoichiometric coefficient.

$$K_p$$

The equilibrium constant for gaseous reactions expressed in terms of partial pressures rather than molar concentrations.

Homogeneous Equilibrium

A chemical equilibrium in which all participating chemical species are in the same state of matter.

Heterogeneous Equilibria

Equilibria involving substances in different phases, such as solids and gases or solids and aqueous solutions.

Relationship between $K_c$ and $K_p$

The mathematical relationship defined by the formula $K_p = K_c(RT)^{\Delta n}$, where $R$ is the ideal gas constant and T is temperature in Kelvin.

Ideal gas constant ($R$)

The constant used in gas-related equilibrium calculations, valued at $0.08206\,L\times atm/mol\times K$.

$$\Delta n$$

The difference between the sums of the coefficients of the gaseous products and the gaseous reactants in a balanced chemical equation.

Haber process

The industrial synthesis of ammonia ($N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$), which is considered optimal for studying chemical equilibria.

Equilibrium Constant Units

The equilibrium constant ($K$) is a unitless value, unlike the reaction rate constant ($k$), which has units.

Product favored

A condition describing a reaction where the equilibrium constant ($K_x$) is greater than one.

Reactant favored

A condition describing a reaction where the equilibrium constant ($K_x$) is less than one.

Reaction Quotient ($Q$)

A value calculated using initial concentrations or pressures to determine the direction a reaction will shift to reach equilibrium.

RICE table

A mnemonic for Reaction, Initial, Change, and Equilibrium; a systematic method used to determine concentration variables to solve equilibrium expressions.

Small $K$ assumption

An approximation used when $K_c$ is less than $1.0 \times 10^{-3}$, assuming the change in concentration is so small that initial and equilibrium concentrations are approximately equal.

Le Châtelier’s Principle

A principle stating that if a system at equilibrium is disturbed by changes in temperature, pressure, or concentration, the system shifts to counteract the disturbance and reestablish equilibrium.

Endothermic reaction

A reaction where $\Delta H^{\circ}$ is positive; raising the temperature shifts the equilibrium to the right and increases the value of $K_{eq}$.

Exothermic reaction

A reaction where $\Delta H^{\circ}$ is negative; raising the temperature shifts the equilibrium to the left and decreases the value of $K_{eq}$.