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AL. OCR Chemistry > Rates + Equilibrium > Flashcards

Rates + Equilibrium Flashcards

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1
Q

rate equation

A

r = K[A][B] etc.

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2
Q

zero order

A

concentration have no effect on the rate

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3
Q

first order

A

rate increases by same factor as concentration increases

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4
Q

second order

A

rate increases by conc increase factor²

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5
Q

rate units

A

mol/dm3/s

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6
Q

half life

A

Time taken for half the reagent to be used up

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7
Q

half life in first order reaction

A

always the same

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8
Q

use of half lives

A

to determine whether or not a reaction is first order

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9
Q

Arrhenius equation shows

A

effect of changing temp/activation energy on the rate constant

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10
Q

Kc equation

A

Kc = [products] / [reactants]

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11
Q

mole fraction equation

A

= moles of gas A \ total moles of gas

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12
Q

partial pressure

A

the pressure one gas would except if it was the only gas in the container

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13
Q

partial pressure equation

A

pp = mol frac. x total pressure

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14
Q

only factor that changes Kc

A

temperature

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15
Q

dynamic equilibrium

A

both the foward and backwards reactions are taking place, at the same rate

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16
Q

dynamic equilibrium

A

both the forwards and backwards reactions are taking place, at the same rate

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17
Q

effect of pressure on position of equilibrium

A

pressure increase = favours the side with fewer gas molecules (reducing pressure of the system)

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18
Q

effect of temperature on position of equilibrium

A

temp increase = favours endothermic reaction

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19
Q

effect of concentration on position of equilibrium

A

conc. increase = favours side with fewer moles

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20
Q

Kc > 1 =

A

equilibrium position is towards PRODUCTS

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21
Q

Kc < 1 =

A

equilibrium position is towards REACTANTS

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22
Q

Kc = 1 =

A

equilibrium is HALFWAY between products and reactants

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23
Q

heterogeneous catalyst

A

catalyst in different phase (state) to reactants

24
Q

homogeneous catalyst

A

catalyst in the same phase (state) as reactants

25
Q

how does a homogeneous catalyst work?

A

forms intermediate species which react to form products and reform the catalyst

26
Q

how does a heterogeneous catalyst work?

A

reaction occurs on its surface (therefore bigger SA = faster rate)

27
Q

rate

A

the change in the amount of reactants or production per unit of time

28
Q

Ea eq.

A

Ea = RT (ln A- Ln K)

29
Q

Arrhenius equation

A

K = Ae [to the power or] -(Ea/RT)

30
Q

gas constant

A

8.31 JK-1mol-1

31
Q

Kp eq.

A

[products partial pressure] / [reactants partial pressure]

32
Q

3 stages of contact process

A

1) sulfur solid is melted and combusted with oxygen = sulfur dioxide
2) sulfur trioxide formed from sulfur dioxide (reversible) with vanadium catalyst (exothermic) - 450 degrees C
3) sulfur trioxide reacted with oleum + conc. sulphuric acid (v. exothermic) to make sulphuric acid

33
Q

uses of H2SO4

A
  • drug manufacture
  • metal treatment
  • paint
  • making explosives
34
Q

how do catalysts reduce damage to environment? (2)

A
  • reactions take place at lower activation energy ∴ less fuel used, less CO2 emitted
  • better atom economy - less hazardous chemicals produced
35
Q

uses of hydrogen? (3)

A
  • fuel cells
  • Haber process
  • hydrogenation of alkenes
36
Q

dynamic equilibrium

A

where the rate of forwards and backwards reactions are the same IN A CLOSED SYSTEM

37
Q

equation for rate constant using half lives

A

k = ln(2) / half life

38
Q

instantaneous rate

A

rate when t=0

39
Q

method for determining Kc experimentally

A
  • in conical flask mix substances
  • add acid catalyst
  • set up another conical flask with same acid catalyst as control
  • stopper both flasks
  • leave for a week so they reach equilibrium
  • carry out titration using NaOH
  • repeat titration with control to determine amount of acid catalyst used
  • analyse to determine eq amounts and concs
  • use kc equation
40
Q

catalyst

A

a species which speeds up a reaction w/o undergoing permanent change itself

41
Q

le Chatiliers principle

A

when a change is imposed on a closed system at equilibria, the position of the equilibrium will shift to minimise the effect of the change

42
Q

temp increase favours

A

ENDOTHERMIC

43
Q

temp decrease favours

A

EXOTHERMIC

44
Q

Kc =

A

[products] / [reactants]

45
Q

Kc > 1 =

A

eq. towards PRODUCTS

46
Q

Kc < 1 =

A

eq. towards REACTANTS

47
Q

K =

A

rate / [A]2

48
Q

methods of continuous rate monitoring (2)

A
  • gas collection

- mass lost

49
Q

K = (using t 1/2)

A

ln2. /t 1/2

50
Q

effect of temp on Kc - (temp up =)

A

rate up = Kc UP

51
Q

Kp =

A

partial pressure (products) / pp. (reactants)

52
Q

conc increase favours…

A

side producing fewer moles

53
Q

conc decrease favours

A

side producing more moles

54
Q

if K is negative ..

A

towards reactants

55
Q

is K is positive …

A

towards products

AL. OCR Chemistry (20 decks)

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