Chapter 13: Reaction Rates and Equilibrium

Question 1

collision theory

Answer 1

chemical reactions are due to collisions of molecules

Question 2

reacting molecules must collide with sufficient energy to

Answer 2

break bonds

Question 3

molecules must collide in an orientation that can lead to

Answer 3

rearrangement of the atoms

Question 4

reaction rate

Answer 4

a measure of how fast a reaction occurs

Question 5

the reaction rate is measured by

Answer 5

an increase in the [products] or a decrease in the [reactants] over time

Question 6

the reaction rate depends on

Answer 6

[reactants], temperature, and activation energy

Question 7

increasing the concentration of reactants

Answer 7

increases the frequency of collisions between molecules because there are more molecules present in a given volume, leading to a higher chance of interactions and potential reactions

Question 8

increasing the temperature

Answer 8

increases the rate of a reaction because molecules collide more frequently and more forcefully, making the molecules more likely to rearrange

Question 9

reaction profile

Answer 9

a diagram showing the progress of a reaction

Question 10

activation energy (Ea)

Answer 10

the minimum amount of kinetic energy that must be supplied to start a chemical reaction; Ea = Ets - Ereactants

Question 11

low barrier (activation energy)

Answer 11

energy required to react is low & high proportion of molecules may have sufficient energy to react = fast rxn

Question 12

high barrier (activation energy)

Answer 12

activation energy is high & only a few molecules will have sufficient energy to react = slow rxn

Question 13

transition state

Answer 13

the highest-energy arrangement of atoms in a chemical reaction

Question 14

net energy change (△E)

Answer 14

E products - E reactants; negative value is exothermic (products are lower in energy, stable) & positive value is endothermic (products are higher in energy, higher potential energy)

Question 15

catalyst

Answer 15

a substance that is not consumed in a rxn, but whose presence increases the rate of a rxn

Question 16

a catalyst increases the rate of a rxn by

Answer 16

lowering the activation energy - more particles will have enough energy for the rxn to occur

Question 17

equilibrium reaction

Answer 17

a reaction that occurs both in the forward and backward direction; the rates of these reactions are the same

Question 18

equilibrium systems are

Answer 18

dynamic (in constant motion); both the fwd and rev rxns are still occurring, but the [reactants] and [products] do not change once equilibrium has been reached

Question 19

the side of an equilibrium that is lower in energy will have a

Answer 19

greater concentration

Question 20

the side of an equilibrium that is higher in energy will have a

Answer 20

smaller concentration

Question 21

equilibrium expression

Answer 21

an equation that describes the balance between reactants and products in an equilibrium

Question 22

equilibrium constant (Keq)

Answer 22

the ratio of [reactants] and [products]; [products] ^ coefficient / [reactants] ^ coefficient

Question 23

the equilibrium constant tells us

Answer 23

whether the equilibrium favors the reactants or products

Question 24

Keq > 1

Answer 24

products are favored over reactants (ex. 1 x 10^3); if a fraction > 1, the numerator is larger than the denominator

Question 25

Keq < 1

Answer 25

reactants are favored over products (ex. 1 x 10^-3); if a fraction < 1, the numerator is smaller than the denominator

Question 26

Keq&raquo_space; 1

Answer 26

rxn goes to completion (ex. 1 x 10^5)

Question 27

Keq &laquo_space;1

Answer 27

rxn “virtually never occurs” (ex. 1 x 10^-5)

Question 28

special rules apply for writing equilibrium expressions in three situations involving

Answer 28

solvents, solids, and gases

Question 29

solvents are not included in equilibrium expressions because

Answer 29

they do not change significantly during a rxn (concentration does not change)

Question 30

when equilibria involve solids, the amount of solid present

Answer 30

does not affect the concentration of the other components; because of this, solids are not included in equilibrium expressions

Question 31

when the only reactant/product is a solid, we put a value of

Answer 31

one in its place

Question 32

solubility product (Ksp)

Answer 32

the equilibrium constant for the solution of an ionic compound

Question 33

as with other equilibrium expressions, a small Ksp value means

Answer 33

the equilibrium lies far to the left - the smaller the Ksp value, the less soluble the compound is

Question 34

equilibrium expressions for gases use

Answer 34

partial pressure

Question 35

Le Châtelier’s principle

Answer 35

the idea that when a change takes place in concentration, temperature, pressure, or other key factors, the equilibrium shifts to minimize that change and a new equilibrium is established

Question 36

increasing the concentration on one side

Answer 36

increases the concentration on the other side & vice versa

Question 37

if we add something to an equilibrium,

Answer 37

it pushes the equilibrium toward the other side

Question 38

if we remove something from the equilibrium,

Answer 38

it pulls the equilibrium toward the side it was removed from

Question 39

with equilibrium and temperature, the change depends on

Answer 39

the nature of the reaction - exothermic = adding heat to product(s) & endothermic = adding heat to reactant(s)

Question 40

changes in pressure will only affect the equilibrium if

Answer 40

one or more of the reactants or products is a gas - increasing the amount of gas increases the pressure

Question 41

increasing the pressure in a chemical system shifts the equilibrium

Answer 41

toward the side with fewer moles of gas

Question 42

decreasing the pressure in a chemical system shifts the equilibrium

Answer 42

towards the side with more moles of gas