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Dynamic Equilibrium

Two opposing processes that occur at the same rate. When reached, the concentrations of the reactants and products does not change—constant but not equal.

Equilibrium

A system is in equilibrium when the forces consisting it are arranged in such a way as to compensate each other, like the two weights pulling the arms of a pair of scales.

Rate

A measure of how fast the reaction proceeds; the amount of reactant that changes to product in a given amount of time.

Collision Theory

Chemical reactions occur through collisions between molecules or atoms.

Concentration vs. Reaction Rate

The higher the concentration the faster the reaction rate because there are more collisions happening in the system.

Temperature vs. Reaction Rate

The higher the temperature the faster the reaction rate because the molecules move faster therefore increasing the rate of collisions. Additionally, the molecules have a higher overall energy which makes reactions more probable

Reversible Reaction

A reaction that can proceed in both directions; uses the symbol, ⇌

Equilibrium Constant

A way to quantify the relative concentrations of the reactants and products at equilibrium. K_eq

K_eq = [C]^c[D]^d/[A]^a[B]^b: (products/reactants)

aA + bB ⇌ cC + dD

The greater the equilibrium constant the greater the concentration of the products vs. the reactants at equilibrium.

Depends on temperature

Heterogeneous Equilibria

Pure solids and liquids not included in the equilibrium constant because their concentrations are constant

Le Châtelier’s principle

When a chemical system at equilibrium is disturbed, the system shifts in a direction that minimizes the disturbance.

Increasing pressure; goes toward lower molar concentration

Decreasing pressure; goes toward higher molar concentration

Adding heat; shifts to the other side

Solubility-Product Constant

An equilibrium constant that reflects the extent to which an ionic compound dissolves in water; K_sp

K_sp = [C]^c[D]^d; (products)

Large K_sp = Very soluble

Small K_sp = Insoluble or Partially Soluble

Activation Energy

The amount of energy that must be overcome in order to start a reaction (activation barrier)

The higher the activation energy, the slow the reaction rate

Concentration, Energy, Catalyst vs. Activation Energy

Increase concentration: increase rate, activation energy stays constant

Increase Temperature: increase rate, activation energy stays constant

Add catalyst: position of reaction stays the same, activation energy lowers

Catalyst

A catalyst is a substance that increases the rate of a chemical reaction but is not consumed by the reaction