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chem > topic 9 + 16 kinetics 1 and 2 > Flashcards

topic 9 + 16 kinetics 1 and 2 Flashcards

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1
Q

effect of changing conc of reactants on rate

A
  • increase conc = more particles per unit volume
  • more frequent successful collisions
  • increased rate
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2
Q

effect of changing pressure of reactants on rate

A
  • same no. particles per smaller unit volume
  • more frequent successful collisions
  • increased rate
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3
Q

effect of changing temperature of reactants on rate

A
  • increases KE of reactants
  • move faster
  • more frequent successful collisions
  • more collisions have energy >= Ea
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4
Q

effect of changing SA of reactants on rate

A
  • increased SA
  • more particles able to react per unit volume
  • more frequent successful collisions
  • increased rate
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5
Q

activation energy

A

minimum amount of energy needed by reactant particles for the reaction to take place

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6
Q

endothermic

A

take in energy

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7
Q

exothermic

A

release energy

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8
Q

activation energy in endothermic

A

LARGER than exo

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9
Q

successful collision is

A
  • collision in the correct orientation
  • energy greater than or equal to activation energy
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10
Q

meausring rate of reaction (mass of gas lost)

A
  • use a BALANCE
  • LIMITATION: gas must be dense enough or change in mass is too small to measure [look at mr]
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11
Q

measuring rate of reaction (volume of gas produced)

A
  • gas syringe
  • collection over water [as long as gas not water soluble]
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12
Q

measuring rate of reaction (concentration changes)

A

-take a sample at a certain point
- quench
- titrate

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13
Q

measuring rate of reaction (disappearing cross)

A

limitation: subjective, only 1 piece of data for analysis

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14
Q

initial rate graph tangent

A

at time = 0

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15
Q

what does the Maxwell-Boltzmann curve show

A

distribution of energies of particles at a certain temperature

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16
Q

higher temp on boltzmann curve

A
  • peak lower and to the right
  • above initial
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17
Q

how does a catalyst work

A
  • increase rate of reaction by providing an alternative pathway with a lower activation energy
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18
Q

homogeneous catalyst

A
  • catalyst in the same phase as the reactants (same state)
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19
Q

heterogeneous catalyst

A
  • catalyst in a different phase to the reactants (different state)
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20
Q

how to show effect of catalsyt on maxwell boltzmann curve

A

move activation energy line to the left (more particles have Ea)

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21
Q

5 ways of measuring rat eof reaction

A
  • mass lost
  • volume of gas produced
  • colorimetry
  • pH change
  • changes in electrical conductivity
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22
Q

first order reactant

A

rate DIRECTLY PROPORTIONAL to conc of reactant

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23
Q

fractional order

A

reaction involves multiple steps

24
Q

0 order

A

changing conc of reactant has no effect on rate
- not in rate equation

25
Q

2nd order

A

rate directly proportional to SQUARE of conc of chemical

26
Q

overall order

A

add together the orders of each reactant

27
Q

units of rate

A

mol/dm3/s

28
Q

colorimetry for coloured precipitates

A

not allowed

29
Q

rate determing step

A

slowest step in the reaction
uses reactants in equation

30
Q

arrhenius equation

A

k = Ae^(-Ea/RT)

31
Q

r

A

ideal gas constant
8.31J

32
Q

Ea unit in equation

A

J/mol

33
Q

graph for arrhenius

A

1/Temperature [k] (x axis)
ln k (y axis)

34
Q

gradient arrhenius

A

m = -Ea/R

35
Q

rate of reaction defintion

A

rate of decrease of concentration of reactants

36
Q

overall order of reaction defintion

A

sum of the powers to which concentration terms are raised in the ocerall rate equations

37
Q

why can you not use just stoichiometric equation to determine order

A

the rate equation only includes the species involved in the rate equation

38
Q

give a reason why the rate equation shows the reaction cant happen in one step

A
  • x molecules in stoichiometric but less in rate
  • collisions with 2+ particles unlikely
39
Q

apparatus to remove samples for quenching

A

volumetric pipette

40
Q

why can you use volume of titre - initial volume of titre on y axis for graph

A

volume is proprotional to concentration of reactant

41
Q

purpose of putting ice in flask before titrating

A
  • quenches reaction
  • slows it down significantly, or reaction would continue produicng x product

OR NO
- reaction slow
- no catalyst used

42
Q

unit of gradeint

A

K

43
Q

why is Ea so high

A
  • lots of energy required for reaction to start
  • to break the strong bonds
  • shows a slow rate of reaction
44
Q

purpose of phenol in experiment

A
  • reacts with bromine
  • when finished, excess bromine bleaches indicator, allowing a point to minotor progress if reaction
45
Q

why is total volume of reactant kept constnat (think serial dilution)

A

so that volume reactant is proprotional to concentration

46
Q

graph of conc v 1/time
assumption needed to use 1/time for rate?

A
  • progress point happens early in reaction
  • where [reactant] against time is almost linear
  • so that the tangent is the same as change in conc/time (rate)
47
Q

if incorrect volume measured, should this be discarded?

A

NO
- plot at correct point on graph
- ensure total volume still constant

48
Q

why measure into boiling tube from burette before reaction mixture

A
  • burette too slow to add
  • start time inaccurate
49
Q

changes to procedure to get overall rate equation

A
  • repeat, varying [other reactatns]
  • keeping all other values constant
50
Q

labels on maxwell boltzmann curve

A

x axis = energy, E
y axis = proportion of particles with energy

51
Q

why does a catalyst have no effect on the products in the reaction

A
  • increases the rate of the forwards and backwards reactions
52
Q

how to check a catalyst works and isnt used up

A
  • filter solid
  • dry
  • reweigh (constant)
  • repeat to see if rate still decreased
53
Q

why is a hetergenous solid catalyst good for a gas reaction

A

provides a surface for the reaction

54
Q

why is initial rate graph method flawed

A
  • harder to draw the tangent for initial than it is for max
55
Q

why is volume of gas a bit higher in high

A

volgas exapnds at high temperatres

chem (12 decks)

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