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A-level chemistry > A2 - Unit 2 - Rates, equilibrium and pH > Flashcards

A2 - Unit 2 - Rates, equilibrium and pH Flashcards

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1
Q

How do you calculate rate?

A

Time

Or

Change in time

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2
Q

What is rate of reaction?

A

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

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3
Q

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

A

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

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4
Q

What is the initial rate of reaction?

A

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

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5
Q

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

A

pH changes by carrying out titrations

pH changes by using a pH meter

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6
Q

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

A

Change in volume or pressure

The loss in mass or reactants

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7
Q

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

A

The formation of a precipitate

A colour change

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8
Q

What is the rate equation?

A

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

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9
Q

What is order?

A

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

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10
Q

What is overall order?

A

The sum of the individual orders m+n

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11
Q

What is the rate constant?

A

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

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12
Q

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

A

The larger the number of collisions per second

the faster the reaction

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13
Q

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

A

The rate is unaffected by changing the concentration of A

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14
Q

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

A

If the concentration is doubled, the rate also doubles

If the concentration increases by three then the rate also triples

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15
Q

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

A

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)

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16
Q

What is the half life of a reactant?

A

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

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17
Q

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

A

The larger the value of K the faster the reaction

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18
Q

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

A

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

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19
Q

What is a reaction mechanism?

A

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

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20
Q

What is the rate-determining step?

A

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

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21
Q

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

A

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

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22
Q

What is an intermediate?

A

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

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23
Q

When does a reaction reach equilibrium?

A

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

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24
Q

What is dynamic equilibrium?

A

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

25
Q

What is a homogeneous equilibrium?

A

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

26
Q

What is heterogeneous equilibrium?

A

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

27
Q

What two things can you find from a balanced equation?

A

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

28
Q

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

A

The reaction is product-favoured

The products on the right-hand side predominate at equilibrium

29
Q

What does a Kc value of 1 mean?

A

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

30
Q

What does a Kc value of less than 1 mean?

A

The reaction is reactant-favoured

The reactants on the left-hand side predominate at equilibrium

31
Q

How does temperature affect Kc?

A

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

32
Q

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

A

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

33
Q

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

A

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

34
Q

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

A

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

35
Q

How does pressure affect the position of the equilibrium?

A

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

36
Q

Does the presence of a catalyst affect pH?

A

Nope!

37
Q

What does a large value for Kc mean?

A

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

38
Q

What happens to Kc if the forward reaction is endothermic?

A

Kc increases with an increase in temperature

39
Q

What happens to Kc if the forward reaction is exothermic?

A

Kc decreases with an increase in temperature

40
Q

What does a large value for K mean?

A

A fast rate of reaction

41
Q

What is K?

A

The rate constant

42
Q

When does K increase?

A

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

43
Q

How do you measure K?

A

Experimentally

44
Q

What is a Bronstead-Lowry acid?

A

A proton donor

45
Q

What is a Bronstead-Lowry base?

A

A proton acceptor

46
Q

What is an alkali?

A

A base that dissolves in water forming OH- ions

47
Q

What is a Lewis acid?

A

An electron-pair acceptor

48
Q

What is a Lewis base?

A

An electron-pair donor

49
Q

What is neutralisation?

A

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

50
Q

What is a monobasic acid and give an example of one

A

An acid which can release one proton

HCl

51
Q

What is a dibasic acid and give an example of one

A

An acid which can release two protons

H2SO4

52
Q

What is a tribasic acid and given an example of one

A

An acid which can release three protons

H3PO4

53
Q

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

A

Carbonates
Bases
Alkalis

54
Q

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

A

H+ + OH- —> H2O

55
Q

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

A

2H+ + CaCO3 —> Ca2+ + CO2 + H2O

56
Q

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

A

2H+ + MgO —> Mg2+ + H2O

57
Q

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

A

H+ + OH- —> H2O

58
Q

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

A

2H+ + Mg —> Mg2+ + H2

59
Q

What is an acid-base pair?

A

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

A-level chemistry (15 decks)

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