chemistry || ch 18 & 16.5: study guide

equilibrium position

used to determine if a reaction has reached equilibrium

law of chemical equilibrium

states that every reaction proceeds to an equilibrium state with a specific Keq

reaction quotient

depends on the initial concentrations of the substances in a reaction

homogenous equilibria

equilibrium condition for reactions in which products and reactants are in the same state

law of mass action

expresses the relative concentration of reactants and products at equilibrium in terms of an equilibrium constant

heterogenous equilibria

equilibrium condition for a chemical reaction involving substances in more than one state

equilibrium constant

the ratio of product concentration to reactant concentration of equilibrium

Keq >>> 1

shifts towards products

Keq <<< 1

shifts towards reactants

Keq = 1

equilibrium

Q > Keq

shifts towards reactants

Q < Keq

shifts towards products

Q = Keq

equilibrium

le chatelier principle

factors affecting chemical equilibrium: changes in concentration, pressure, temperature

concentration: reactant is added

shifts towards products

concentration: reactant is removed

shifts towards reactants

concentration: product is added

shifts towards reactants

concentration: product is removed

shifts towards products

pressure: increase in pressure

shifts towards side with least number of moles of gas

pressure: decrease in pressure

shifts towards side with most number of moles of gas

temperature: endothermic, increase in temperature

shifts towards products

temperature: endothermic, decrease in temperature

shifts towards reactants

temperature: exothermic, increase in temperature

shifts towards reactants

temperature: exothermic, decrease in temperature

shifts towards products

ΔS+, ΔH-, ΔG-

spontaneous at all T

ΔS+, ΔH+, ΔG+/-

spontaneous at high T, at low T rxn will go in reverse

ΔS-, ΔH-, ΔG+/-

spontaneous at low T, at high T rxn will go in reverse

ΔS-, ΔH+, ΔG+

non-spontaneous at all T

enthalpy of formation (remember formula!)

energy change when one mol of a substance is formed from its elements at standard conditions; unit Kj/mol

entropy (remember formula!)

measurement of disorder, randomness; unit J/K*mol

gibbs free energy

the energy available to do work; energy stored in chemical bonds; temperature dependent

ΔG<0

forward reaction

ΔG>0

reverse reaction

ΔG=0

equilibrium

equilibrium temperature

set ΔG to 0

the equilibrium concentration of products is much greater than that of reactants

Keq is much greater than 1

the equilibrium concentration of products is much less than that of reactants

Keq is much less than 1

there is a considerable amount of both reactants and products at equilibrium

Keq is about equal to 1