A2 - Unit 2 - Rates, equilibrium and pH

Question 1

How do you calculate rate?

Answer 1

Time

Or

Change in time

Question 2

What is rate of reaction?

Answer 2

The change in concentration of a reactant or product per unit time

Question 3

Why does the rate of reaction slow down as the reaction proceeds?

Answer 3

Fewer collisions take place per second between reactant particles
The rate slows down

Question 4

What is the initial rate of reaction?

Answer 4

The change in concentration of a reactant or product per unit time at the start of the reaction when t=0

Question 5

What can you use to measure pH changes for reactions involving acids or bases?

Answer 5

pH changes by carrying out titrations

pH changes by using a pH meter

Question 6

What can you measure when trying to produce a rate graph?

Answer 6

Change in volume or pressure

The loss in mass or reactants

Question 7

When performing reactions that produce visual changes what can you observe?

Answer 7

The formation of a precipitate

A colour change

Question 8

What is the rate equation?

Answer 8

rate = k[A]m[B]n
where:
m = the order of reaction with respect to A
n = the order of reaction with respect to B

Question 9

What is order?

Answer 9

With respect to a reactant is the power to which the concentration of the reactant is raised in the rate equation

Question 10

What is overall order?

Answer 10

The sum of the individual orders m+n

Question 11

What is the rate constant?

Answer 11

The constant that links the rate of reaction with the concentrations of the reactants raised to the powers of their orders in the rate equation

Question 12

What happens to the reaction when there is a greater concentration?

Answer 12

The larger the number of collisions per second

the faster the reaction

Question 13

If the reaction is zero order what happens if you change the concentration?

Answer 13

The rate is unaffected by changing the concentration of A

Question 14

If the reaction is first order what happens when you change the concentration?

Answer 14

If the concentration is doubled, the rate also doubles

If the concentration increases by three then the rate also triples

Question 15

If the reaction is second order what happens when you change the concentration?

Answer 15

If you double the concentration then the rate increases by 4 times (2 squared)
If you triple the concentration then the rate increases by 9 (3 squared)

Question 16

What is the half life of a reactant?

Answer 16

The time taken for the concentration of the reactant to reduce by half

Question 17

What happens to the reaction when the value of K increases?

Answer 17

The larger the value of K the faster the reaction

Question 18

What effect does an increase in temperature have on the rate constant k?

Answer 18

Increase in temp
More energy in molecules
More frequent collisions
More molecules exceed the activation energy
Rate increases with temperature
which is shown by an increase in the rate constant

Question 19

What is a reaction mechanism?

Answer 19

A series of steps that, together, make up the overall reaction

Question 20

What is the rate-determining step?

Answer 20

The slowest step in the reaction mechanism of a multi-step reaction

Question 21

Why is the overall rate affected by the rate-determining step?

Answer 21

A slow step becomes an obstacle to the whole process - reactants can become products only as fast as they can get through this slow step
The overall reaction can be no faster than the slowest step

Question 22

What is an intermediate?

Answer 22

A species formed in one step of a multi-step reaction that is used up in a subsequent step, and is not seen as either a reactant or a product of the overall equation

Question 23

When does a reaction reach equilibrium?

Answer 23

The rate of the forward reaction is the same as the rate of the reverse reaction
The concentrations of the reactants and the products remain the same
Reaction is in a close system

Question 24

What is dynamic equilibrium?

Answer 24

Exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction

Question 25

What is a homogeneous equilibrium?

Answer 25

An equilibrium in which all the species making up the reactants and products are in the same physical state

Question 26

What is heterogeneous equilibrium?

Answer 26

An equilibrium in which species making up the reactants and products are in different physical states

Question 27

What two things can you find from a balanced equation?

Answer 27

The reacting quantities needed to prepare a required quantity of product The quantities of products formed by reacting together known quantities of reactants

Question 28

What happens to the equation when Kc is larger than 1?

Answer 28

The reaction is product-favoured | The products on the right-hand side predominate at equilibrium

Question 29

What does a Kc value of 1 mean?

Answer 29

Indicated the position of the equilibrium is halfway between reactants and products

Question 30

What does a Kc value of less than 1 mean?

Answer 30

The reaction is reactant-favoured | The reactants on the left-hand side predominate at equilibrium

Question 31

How does temperature affect Kc?

Answer 31

An increase in temp shifts the position of equilibrium in the endothermic direction A decrease in temp shifts the position of the equilibrium into the exothermic direction

Question 32

If the forward direction of a reaction is endothermic and the temperature increases, what happens to Kc?

Answer 32

It also increases The equilibrium yield of the products on the right-hand side increases The equilibrium yield of the reactants on the left-hand side decreases

Question 33

When the forward reaction is exothermic and the temperature increases what happens to Kc?

Answer 33

Kc decreases The equilibrium yield of the products on the right-hand side decreases The equilibrium yield of the reactant on the left-hand side increases

Question 34

How does changes in concentration affect the position of the equilibrium?

Answer 34

The equilibrium shifts to the side with the lowest concentration to alter the changes

Question 35

How does pressure affect the position of the equilibrium?

Answer 35

If the pressure is doubled the concentrations of the gases will also double The equilibrium shifts to restore the ratio back by favouring the side with the least gas moles

Question 36

Does the presence of a catalyst affect pH?

Answer 36

Nope!

Question 37

What does a large value for Kc mean?

Answer 37

The position of the equilibrium lies well to the right-hand side. In favour of the products

Question 38

What happens to Kc if the forward reaction is endothermic?

Answer 38

Kc increases with an increase in temperature

Question 39

What happens to Kc if the forward reaction is exothermic?

Answer 39

Kc decreases with an increase in temperature

Question 40

What does a large value for K mean?

Answer 40

A fast rate of reaction

Question 41

What is K?

Answer 41

The rate constant

Question 42

When does K increase?

Answer 42

With an increase in temperature, so rate increases with increasing temperature

Question 43

How do you measure K?

Answer 43

Experimentally

Question 44

What is a Bronstead-Lowry acid?

Answer 44

A proton donor

Question 45

What is a Bronstead-Lowry base?

Answer 45

A proton acceptor

Question 46

What is an alkali?

Answer 46

A base that dissolves in water forming OH- ions

Question 47

What is a Lewis acid?

Answer 47

An electron-pair acceptor

Question 48

What is a Lewis base?

Answer 48

An electron-pair donor

Question 49

What is neutralisation?

Answer 49

A chemical reaction in which an acid and a base react together to produce a salt and water

Question 50

What is a monobasic acid and give an example of one

Answer 50

An acid which can release one proton | HCl

Question 51

What is a dibasic acid and give an example of one

Answer 51

An acid which can release two protons | H2SO4

Question 52

What is a tribasic acid and given an example of one

Answer 52

An acid which can release three protons | H3PO4

Question 53

What three things do aqueous acids react with in typical acid-base reactions

Answer 53

Carbonates Bases Alkalis

Question 54

What is the ionic equation for a neutralisation reaction including HCl, HNO3 and H2SO4?

Answer 54

H+ + OH- ---> H2O

Question 55

What is the ionic equation for a neutralisation reaction with carbonates? e.g. with CaCO3

Answer 55

2H+ + CaCO3 ---> Ca2+ + CO2 + H2O

Question 56

What is the ionic equation for the neutralisation reaction with bases? e.g. MgO

Answer 56

2H+ + MgO ---> Mg2+ + H2O

Question 57

What is the ionic equation for the neutralisation reaction with alkalis? e.g. KOH

Answer 57

H+ + OH- ---> H2O

Question 58

What is the ionic equation for the redox reaction of an acid and a metal? e.g. Mg

Answer 58

2H+ + Mg ---> Mg2+ + H2

Question 59

What is an acid-base pair?

Answer 59

A pair of two species that transform into each other by gain or loss of a proton