Chapter 15: Chemical Equilibrium

Question 1

What is chemical equilibrium?

Answer 1

occurs when the forward and reverse reactions proceed at equal RATES

Question 2

What is an equilibrium state?

Answer 2

mixture of reactants and product whose concentrations no longer change with time

Question 3

What must equilibrium mixtures must be?

Answer 3

REVERSIBLE

Question 4

What is required in order for equilibrium to occur?

Answer 4

neither reactants nor products can escape from the system

Question 5

What is the Haber process?

Answer 5

catalyst system and conditions of temp(T) and pressure for the formation of NH3, N2 and H2

Question 6

Who developed the Haber process?

Answer 6

Fritz Haber

Question 7

What is the law of mass action?

Answer 7

(any reaction) relationships between the concentrations of reactants and products present at equilibrium which condition is described by an equilibrium constant expression

Question 8

Who developed the law of mass action?

Answer 8

Cato Maximillian Guldberg and Perter Waage

Question 9

What is the equilibrium constant for concentration?

Answer 9

Kc

Question 10

What is the equilibrium constant for pressure?

Answer 10

Kp

Question 11

What does the equilibrium constant depend only on?

Answer 11

stoichiometry fo the reaction

Question 12

What does the equilibrium constant not depend on?

Answer 12

mechanism of reaction | initial amounts of reactants/products

Question 13

What are the units for the equilibrium constants of pressure and concentration?

Answer 13

NO UNITS!!!

Question 14

What does an equilibrium constant K&raquo_space; 1 indicate?

Answer 14

large k = equilibrium shifts RIGHT = products dominate

Question 15

What does an equilibrium constant K &laquo_space;1 indicate?

Answer 15

small k = equilibrium shifts LEFT = reactants dominate

Question 16

What is homogenous equilibria?

Answer 16

equilibria involving substances of all the SAME PHASE

Question 17

What is heterogenous equilibria?

Answer 17

equilibria involving substances of DIFFERENT PHASES

Question 18

What states are not included in the equilibrium constant expression/equation? Why?

Answer 18

solids and liquids | concentrations of liquids/solids = constant …. concentrations of products/reactants in the expression are variable

Question 19

What are the 2 things that equilibrium constant allows us to do?

Answer 19

predict the direction the reaction will reach equilibrium | calculate the equilibrium concentrations of products and reactants

Question 20

What is the reaction quotient (Q)?

Answer 20

obtained by substituting reactant/product concentrations/partial pressures AT ANY POINT DURING REACTION into the equilibrium constant expression

Question 21

How can one use the reaction quotient (Q) to analyze the reaction progress?

Answer 21

Compare it with the equilibrium constant (K)

Question 22

What does a reaction quotient (Q) < equilibrium constant (K) indicate?

Answer 22

[reactants] too much // [products] too little = need more products = shift RIGHT

Question 23

What does a reaction quotient (Q) > equilibrium constant (K) indicate?

Answer 23

[reactants] too little // [products] too much = need more reactants = shift LEFT

Question 24

What does a reaction quotient (Q) = equilibrium constant (K) indicate?

Answer 24

system is at equilibrium

Question 25

What is Le Chatlier's Principle?

Answer 25

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

Question 26

Who developed Le Chatlier's Principle?

Answer 26

Henri-Louis Le Chatlier

Question 27

Based on Le Chatlier's Principle, what occurs when a substance is added?

Answer 27

system reacts to consume it

Question 28

Based on Le Chatlier's Principle, what occurs when a substance is removed?

Answer 28

system reacts to produce more of it

Question 29

Based on Le Chatlier's Principle, what must be changed in order to change the pressure of the system?

Answer 29

change volume

Question 30

Based on Le Chatlier's Principle, what occurs when a volume is increased?

Answer 30

shift to produce MORE gas molecules

Question 31

Based on Le Chatlier's Principle, what occurs when a volume is decreased?

Answer 31

shift to produce LESS gas molecules

Question 32

Based on Le Chatlier's Principle, what occurs when a temperature is INCREASED in a ENDOTHERMIC reaction?

Answer 32

shift RIGHT = increase K

Question 33

Based on Le Chatlier's Principle, what occurs when a temperature is DECREASED in a ENDOTHERMIC reaction?

Answer 33

shift LEFT

Question 34

Based on Le Chatlier's Principle, what occurs when a temperature is INCREASED in a EXOTHERMIC reaction?

Answer 34

shift LEFT = decrease K

Question 35

Based on Le Chatlier's Principle, what occurs when a temperature is DECREASED in a EXOTHERMIC reaction?

Answer 35

shift RIGHT

Question 36

What is a catalyst?

Answer 36

increases the rate that the system reaches equilibrium BUT does NOT change the composition of the equilibrium mixture