Chapter 15: Chemical Equilibrium Flashcards
What is chemical equilibrium?
occurs when the forward and reverse reactions proceed at equal RATES
What is an equilibrium state?
mixture of reactants and product whose concentrations no longer change with time
What must equilibrium mixtures must be?
REVERSIBLE
What is required in order for equilibrium to occur?
neither reactants nor products can escape from the system
What is the Haber process?
catalyst system and conditions of temp(T) and pressure for the formation of NH3, N2 and H2
Who developed the Haber process?
Fritz Haber
What is the law of mass action?
(any reaction) relationships between the concentrations of reactants and products present at equilibrium which condition is described by an equilibrium constant expression
Who developed the law of mass action?
Cato Maximillian Guldberg and Perter Waage
What is the equilibrium constant for concentration?
Kc
What is the equilibrium constant for pressure?
Kp
What does the equilibrium constant depend only on?
stoichiometry fo the reaction
What does the equilibrium constant not depend on?
mechanism of reaction | initial amounts of reactants/products
What are the units for the equilibrium constants of pressure and concentration?
NO UNITS!!!
What does an equilibrium constant K»_space; 1 indicate?
large k = equilibrium shifts RIGHT = products dominate
What does an equilibrium constant K «_space;1 indicate?
small k = equilibrium shifts LEFT = reactants dominate
What is homogenous equilibria?
equilibria involving substances of all the SAME PHASE
What is heterogenous equilibria?
equilibria involving substances of DIFFERENT PHASES
What states are not included in the equilibrium constant expression/equation? Why?
solids and liquids | concentrations of liquids/solids = constant …. concentrations of products/reactants in the expression are variable
What are the 2 things that equilibrium constant allows us to do?
predict the direction the reaction will reach equilibrium | calculate the equilibrium concentrations of products and reactants
What is the reaction quotient (Q)?
obtained by substituting reactant/product concentrations/partial pressures AT ANY POINT DURING REACTION into the equilibrium constant expression
How can one use the reaction quotient (Q) to analyze the reaction progress?
Compare it with the equilibrium constant (K)
What does a reaction quotient (Q) < equilibrium constant (K) indicate?
[reactants] too much // [products] too little = need more products = shift RIGHT
What does a reaction quotient (Q) > equilibrium constant (K) indicate?
[reactants] too little // [products] too much = need more reactants = shift LEFT
What does a reaction quotient (Q) = equilibrium constant (K) indicate?
system is at equilibrium
What is Le Chatlier’s Principle?
if a system at equilibrium is disturbed by change in temp(T), pressure or concentration = system will shift its equilibrium to counteract this change to get at equilibrium
Who developed Le Chatlier’s Principle?
Henri-Louis Le Chatlier
Based on Le Chatlier’s Principle, what occurs when a substance is added?
system reacts to consume it
Based on Le Chatlier’s Principle, what occurs when a substance is removed?
system reacts to produce more of it
Based on Le Chatlier’s Principle, what must be changed in order to change the pressure of the system?
change volume
Based on Le Chatlier’s Principle, what occurs when a volume is increased?
shift to produce MORE gas molecules
Based on Le Chatlier’s Principle, what occurs when a volume is decreased?
shift to produce LESS gas molecules
Based on Le Chatlier’s Principle, what occurs when a temperature is INCREASED in a ENDOTHERMIC reaction?
shift RIGHT = increase K
Based on Le Chatlier’s Principle, what occurs when a temperature is DECREASED in a ENDOTHERMIC reaction?
shift LEFT
Based on Le Chatlier’s Principle, what occurs when a temperature is INCREASED in a EXOTHERMIC reaction?
shift LEFT = decrease K
Based on Le Chatlier’s Principle, what occurs when a temperature is DECREASED in a EXOTHERMIC reaction?
shift RIGHT
What is a catalyst?
increases the rate that the system reaches equilibrium BUT does NOT change the composition of the equilibrium mixture
