Unit 10 equilibrium

reversible reactions

products can reform to react to the reactants

chemical equilibrium

rates of the chemical reactions are exactly equal

requirements for equilibrium

reversible reactions, closed system, and a constant temperature

law of mass action

expresses the relative concentrations of reactants and products at equilibrium in terms of a quantity called the equilibrium constant, K_eq

Keq very large/very small

if large then products will be greater then reactants. If small, equation will favor reactants

reaction quotient

used to determine if the reaction is at equilibrium or not

Quotient definition

Q<Keq - more reactants at measurement. Reaction needs to proceed to the right to reach equation.
Q>Keq - more products at measurement. Reaction needs to proceed to the left to reach the equation

Q=Keq At equilibrium no shift in direction

La Chatlier principle

If a system at equilibrium is subjected to a stress, the equilibrium is shifted in the direction that relieves the stress.

La chatlier factors

• Concentration

• Temperature
  (*changes K_eq)

• Pressure
  (gases only)

Temperature decreases (what does it do to equilibrium)

Equilibrium will shift to the left, keq equation will decrease

Changes in pressure

Equilibrium shifts to the side with fewer moles of gas

Catalysts

Adding a catalyst speeds up the rate of reaction