Equilibrium

chemical equilibrium
the state in which the concentrations of reactants and products remain constant with time because the rate at which they are formed in each reaction equals the rate at which they are consumed in the opposite reaction.
reversible reactions
a chemical reaction in which the products can regenerate the original reactants.
law of mass action
expresses the relative concentrations of reactants and products at equilibrium in terms of a quantity called the equilibrium constant.
equilibrium constant
found by an equilibrium expression. measure of the extent to which a reaction proceeds to completion.
law of chemical equilibrium
every reversible reaction proceeds to an equilibrium state that has a specific ratio of the concentrations of reactants and products expressed by Keq
Keq =
[C]^c[D]^d/[A]^a[B]^b from aA + bB <=> cC + dD
equilibrium position
set of equilibrium concentrations. there is an infinite number of these, but only on equilibrium constant.
homogenous equilibria
equilibrium conditions for reactions in which all the reactants and products are in the same state.
heterogenous equilibria
equilibrium conditions for reactions that involve substances in more than one state.
reaction quotient (Q)
is used to determine if a reaction is at equilibrium. if QKeq, reaction will proceed to left (reactants). If Q = Keq, system is at equilibrium, and no shift will occur.
Le Chatelier’s Principle
If a change in conditions is imposed on a system at equilibrium, the equilibrium position will shift in the direction that tends to reduce that change in conditions.
Haber process
An industrial process through which ammonia is synthesized. The process depends upon Le Chatelier’s principle to maximize the yield of ammonia.
dissolution
the process in which an ionic solid dissolves in a polar liquid.
precipitation
the process by which ions leave a solution and regenerate an ionic solid.
solubility equilibrium
when a saturated solution of ions and the remaining solid are in chemical equilibrium.
solubility product (Ksp)
used for aqueous solutions of dissociated ions
ion product (Q)
can be compared with the solubility product to determine if an aqueous solution of ions is supersaturated and will form a precipitate.
precipitation reaction
a reaction in which two solutions are mixed and a precipitate forms. described by balanced equations.
complete ionic equation
equation that shows all soluble ionic substances as ions. found by writing each original solution as the sum of its constituent ions.
spectator ions
ions that do not take place in the chemical reaction and are found in solution both before and after the reaction.
net ionic equation
complete ionic equation minus the spectator ions. includes only those compounds and ions that undergo a chemical change in a reaction in an aqueous solution.
common-ion effect
shift in equilibrium that occurs because the concentration of an ion that is part of the equilibrium is changed.