chem 2

Closed System

A system in which no reactant or product can enter or leave, which is a requirement for a reaction to reach equilibrium.

Dynamic Equilibrium

A state of balance where all reactants and products are present and continuously reacting in both forward and reverse directions at equal rates.

Approximation Rule for ICE Tables

If $\frac{C_i}{K_{eq}} > 500$, the change in initial concentration is negligible and the approximation is justified. If $\frac{C_i}{K_{eq}} < 100$, the full quadratic equation must be solved.

Reaction Quotient ($Q$)

A value calculated by substituting current or initial concentrations into the equilibrium expression to determine which direction the system will shift to reach equilibrium.

$$Q > K_{eq}$$

The concentration of products is higher than at equilibrium, so the system shifts to the left (towards reactants) to attain equilibrium.

$$Q < K_{eq}$$

The concentration of reactants is higher than at equilibrium, so the system shifts to the right (towards products) to attain equilibrium.

Le Chatelier's Principle

States that if a stress or disturbance is applied to a system at chemical equilibrium, the equilibrium will shift in a direction that relieves the stress.