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Chemistry: Module 5 > 5.1 Rates, equilibrium and pH > Flashcards

5.1 Rates, equilibrium and pH Flashcards

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1
Q

What is ‘rate of reaction’?

A

the speed at which a chemical reaction takes place

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2
Q

What does order mean?

A

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

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3
Q

What is a rate constant?

A

the rate constant, k, is a proportionality constant that links the rate of reaction with the concentration of reactants

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4
Q

What is the definition of half-life?

A

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

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5
Q

What is the rate-determining step?

A

the slowest step of the reaction, that determines the rate of the whole reaction

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6
Q

What are the units for rate of reaction

A

mol dm-3 s-1

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7
Q

How do you calculate rate constant, k?

A

k = ln(2) / t1/2 (half life(s))

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8
Q

Describe a zero order rate-concentration graph

A

straight horizontal line
y-intercept gives rate constant, k
changes in conc have no effect on rate

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9
Q

Describe a first order rate-concentration graph

A

straight line through origin
rate directly proportional to conc
rate constant is gradient

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10
Q

Describe a second order rate-concentration graph

A

upward curve with increasing gradient - from origin
2nd graph of rate-(conc)^2 drawn to find rate constant - gradient of 2nd line

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11
Q

Describe a zero order concentration-time graph

A

straight line with negative gradient
reaction rate doesnt change
gradient=k
half life decreases

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12
Q

Describe a first order concentration-time graph

A

downwards curve - decreasing gradient
half life is constant - time for reactant to half each time

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13
Q

Describe a second order concentration-time graph

A

downwards curve, steeper at start
half life increases with time

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14
Q

How does an increase in temperature affect the rate of reaction and rate constant?

A

rate increases - boltzsman distribution shifts to the right so more particles overcome Ea
- particles move faster and collide more frequently

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15
Q

What is the definition of mole fraction?

A

a measure of how much of a given substance is present in a reaction mixture

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16
Q

What is the equation for mole fraction?

A

xA = number of moles of substance A / total number of moles

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17
Q

What is the definition of partial pressure?

A

the pressure an individual gaseous substance would exert if it occupied a whole reaction vessel on its own

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18
Q

What is the equation for partial pressure?

A

mole fraction * total pressure

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19
Q

Which methods can determine concentrations at equilibrium?

A

titrations
using a colorimeter

20
Q

How to determine concentrations at equilibrium using a titration?

A
21
Q

How to determine concentrations at equilibrium using a colorimeter?

A
22
Q

What is the effect of an increase temperature on Kc

A

exothermic - Kc decreases
endothermic - Kc increases

23
Q

Does pressure affect Kc?

A

No

24
Q

What happens to Kc if the concentrations increase?

A

Kc stays the same as the concentrations will change to restore the original Kc

25
Q

What is the effect of a catalyst on a reaction?

A

increases rate of forwards and backwards reaction by the same amount
lowers activation energy
reaction can take place at a lower temperature
cheaper

26
Q

What is the effect of increasing pressure on Kc?

A

increased pressure = increases concentrations
so Kc will stay the same as concentrations will change to revert Kc to original

27
Q

What is a Bronston-Lowry acid?

A

an acid that donates a proton

28
Q

What is a Bronston-Lowry base?

A

a base that accepts a proton

29
Q

What is the equation to work out pH?

A

pH = -log [H+]

30
Q

What is the equation that calculates [H+]?

A

[H+] = 10^ (-pH)

31
Q

What is a conjugate acid-base pair?

A

a set of 2 species that change into one another by gaining or losing a H+ ion
they have a difference of 1 H+ ion

32
Q

What is a mono-basic acid? (give an example)

A

acid that releases 1 H+ proton
e.g. HCl

33
Q

What is a di-basic acid? (give an example)

A

acid that releases 2H+ protons
e.g. H2SO4

34
Q

What is a tri-basic acid? (give an example)

A

acid that releases 3 H+ protons
e.g. H3PO4

35
Q

What type of acid is CH3COOH ?

A

monobasic acid - the cooh group only counts

36
Q

acid + carbonate

A

salt + carbon dioxide + water

37
Q

acid + base

A

salt + water

38
Q

acid + alkali

A

salt + water

39
Q

(redox)
acid + metal

A

salt + hydrogen

40
Q

What does the acid dissociation constant, Ka show?

A

the actual extent of acid dissociation measured by an equilibrium constant

41
Q

What is Ka for
HA(aq) —— H+ (aq) + A- (aq)

A

Ka = [A-][H+] / [HA]

42
Q

What does a large Ka value show?

A

a large extent of dissociation - a strong acid

43
Q

What does a small Ka value indicate?

A

small extent of dissociation - a weak acid

44
Q

What is the equation to find pKa and Ka?

A

pKa = -log10(Ka)
Ka = 10^(-pKa)

45
Q

What does a large and small pKa value show?

A

small pKa value - stronger acid
high pKa value - weaker acid

46
Q

What does a low pH value show?

A

a high concentration of H+

47
Q

What does a high pH value show?

A

a low concentration of H+ ions

Chemistry: Module 5 (3 decks)

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