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Chemistry (Tara) > Rates of Reaction > Flashcards

Rates of Reaction Flashcards

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1
Q

rate of reaction

A

the rate of a chemical reaction is defined as the change in concentration per unit time of any one reactant or product

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2
Q

MONITORING THE ARTE OF PRODUCTION OF OXYGEN FROM HYDROGEN PEROXIDE, USING MANGANESE DIOXIDE AS A CATALYST
theory behind experiment

A

hydrogen peroxide decomposes slowly into water and oxygen gas, the rate of decomposition can be greatly increased with the addition of the catalyst, manganese dioxide

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3
Q

MONITORING THE ARTE OF PRODUCTION OF OXYGEN FROM HYDROGEN PEROXIDE, USING MANGANESE DIOXIDE AS A CATALYST
equation

A

H2O2 -MnO2-> H2O + 1/2 O2

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4
Q

MONITORING THE ARTE OF PRODUCTION OF OXYGEN FROM HYDROGEN PEROXIDE, USING MANGANESE DIOXIDE AS A CATALYST
where do you place the manganese oxide?

A

in a weighing bottle in the hydrogen peroxide solution

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5
Q

MONITORING THE ARTE OF PRODUCTION OF OXYGEN FROM HYDROGEN PEROXIDE, USING MANGANESE DIOXIDE AS A CATALYST
first step

A

knock the weighing bottle into the hydrogen peroxide using the cotton thread and stop clock started immediately

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6
Q

MONITORING THE ARTE OF PRODUCTION OF OXYGEN FROM HYDROGEN PEROXIDE, USING MANGANESE DIOXIDE AS A CATALYST
where do you collect the oxygen gas

A

from the inverted graduated cylinder (downward displacement of water)

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7
Q

MONITORING THE ARTE OF PRODUCTION OF OXYGEN FROM HYDROGEN PEROXIDE, USING MANGANESE DIOXIDE AS A CATALYST
recording

A

volume of oxygen recorded every 3 seconds until it is constant

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8
Q

MONITORING THE ARTE OF PRODUCTION OF OXYGEN FROM HYDROGEN PEROXIDE, USING MANGANESE DIOXIDE AS A CATALYST
how does manganese dioxide look

A

black powder

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9
Q

MONITORING THE ARTE OF PRODUCTION OF OXYGEN FROM HYDROGEN PEROXIDE, USING MANGANESE DIOXIDE AS A CATALYST
repeat

A

without catalyst and results compared

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10
Q

MONITORING THE ARTE OF PRODUCTION OF OXYGEN FROM HYDROGEN PEROXIDE, USING MANGANESE DIOXIDE AS A CATALYST
conclusion

A

the rate of the reaction at the start of the experiment was very fast, however as time went on the rate began to slow down and eventually stopped (level graph)

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11
Q

how to measure average rate

A

total volume of oxygen/total time

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12
Q

to find instantaneous rate

A

draw a tangent to the cur

find the slope of the tangent

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13
Q

5 factors that affect the rate of a chemical reaction

A 
nature of chemicals (ionic/covalent)
particle size (one is solid)
concentration
temperature
catalysts
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14
Q

which are faster in general ionic or covalent reactions

A

ionic

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15
Q

why are ionic reactions usually faster

A

coming together of ions vs bonds formed again

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16
Q

the larger the size of the particle

A

the slower the reaction - less surface area

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17
Q

if finely divided particles are used

A

a dust explosion may happen

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18
Q

5 conditions necessary for a dust explosion to happen

A

dust must be: combustible, dry
oxygen present
enclosed space
source of ignition

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19
Q

HOW PARTICLE SIZE CAN AFFECT REACTION RATE

reactants

A

calcium carbonate (marble) and dilute hydrochloric acid

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20
Q

HOW PARTICLE SIZE CAN AFFECT REACTION RATE

equation

A

CaCO3 + 2HCl -> CaCl2 + H2O + CO2

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21
Q

HOW PARTICLE SIZE CAN AFFECT REACTION RATE

first step

A

weigh out conical flask and cotton wool
weigh marble chips and add to flask with cotton in mouth
weigh put dilute HCl and quicly add to flask (remove plug and put back)

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22
Q

HOW PARTICLE SIZE CAN AFFECT REACTION RATE

after HCl added

A

quickly put flask on electronic balance and start the stop clock

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23
Q

HOW PARTICLE SIZE CAN AFFECT REACTION RATE

stop clock has started

A

take mass every 30 seconds

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24
Q

HOW PARTICLE SIZE CAN AFFECT REACTION RATE

what is the loss in mass due to

A

the carbon dioxide lost through the cotton wool plug

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25
Q

HOW PARTICLE SIZE CAN AFFECT REACTION RATE

how to calculate loss in mass

A

subtracting each mass from the initial mass before reaction started

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26
Q

HOW PARTICLE SIZE CAN AFFECT REACTION RATE

graph

A

loss in mass over time

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27
Q

HOW PARTICLE SIZE CAN AFFECT REACTION RATE

how to prove for particle size

A

graph results for different sizes of marble chips

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28
Q

the greater the concentration

A

the faster the reaction, generally

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29
Q

why is it faster for greater concentrations

A

a greater chance of reactants colliding with each other successfully

30
Q

if temperature increased, and why

A

faster, more kinetic energy, more collisions

31
Q

do catalysts always speed up reaction rates

A

no

32
Q

catalyst that slows down the decomposition of hydrogen peroxide

A

glycerine

33
Q

if a catalyst slows something down what is it called

A

a negative catalyst or inhibitor

34
Q

TO STUDY THE EFFECTS ON THE REACTION OF (I) CHANGING CONCENTRATION (II) CHANGING TEMPERATURE, USING SODIUM THIOSULFATE AND HYDROCHLORIC ACID
equation

A

Na2S2O3 + 2HCl -> s(↓) + 2NaCl + SO2

35
Q

TO STUDY THE EFFECTS ON THE REACTION OF (I) CHANGING CONCENTRATION (II) CHANGING TEMPERATURE, USING SODIUM THIOSULFATE AND HYDROCHLORIC ACID
what can you measure

A

the visibility of the cross drawn underneath

36
Q

TO STUDY THE EFFECTS ON THE REACTION OF (I) CHANGING CONCENTRATION (II) CHANGING TEMPERATURE, USING SODIUM THIOSULFATE AND HYDROCHLORIC ACID
first step

A

known volume and molarity of sodium thiosulfate poured into a conical flask, placed on a piece of paper with an x drawn on it

37
Q

TO STUDY THE EFFECTS ON THE REACTION OF (I) CHANGING CONCENTRATION (II) CHANGING TEMPERATURE, USING SODIUM THIOSULFATE AND HYDROCHLORIC ACID
step 2

A

known volume and molarity of HCl added and stop clock started

38
Q

TO STUDY THE EFFECTS ON THE REACTION OF (I) CHANGING CONCENTRATION (II) CHANGING TEMPERATURE, USING SODIUM THIOSULFATE AND HYDROCHLORIC ACID
step 3

A

swirl flask and stop clock when cross no longer visible

39
Q

TO STUDY THE EFFECTS ON THE REACTION OF (I) CHANGING CONCENTRATION (II) CHANGING TEMPERATURE, USING SODIUM THIOSULFATE AND HYDROCHLORIC ACID
how to examine concentrations

A

procedure repeated using other concentrations of sodium thiosulfate and times notes

40
Q

TO STUDY THE EFFECTS ON THE REACTION OF (I) CHANGING CONCENTRATION (II) CHANGING TEMPERATURE, USING SODIUM THIOSULFATE AND HYDROCHLORIC ACID
graph for concentrations

A

rate vs M

41
Q

TO STUDY THE EFFECTS ON THE REACTION OF (I) CHANGING CONCENTRATION (II) CHANGING TEMPERATURE, USING SODIUM THIOSULFATE AND HYDROCHLORIC ACID
how to do for temperature

A

note temperature at the start and then repeat using various temperatures, heated by bunsen burne r

42
Q

TO STUDY THE EFFECTS ON THE REACTION OF (I) CHANGING CONCENTRATION (II) CHANGING TEMPERATURE, USING SODIUM THIOSULFATE AND HYDROCHLORIC ACID
graph for temperature

A

reaction vs absolute temperature

43
Q

catalyst

A

a substance that alters the rate of a chemical reaction but is not used up during the reaction

44
Q

4 general properties of catalysts

A

remain chemically unchanged
specific
reversible in their action
catalyst poisons

45
Q

may catalysts be physically changed by the end of a reaction?

A

yes, just not chemically

46
Q

what does it mean to be reversible in their action

A

they catalyse both forward and reverse reactions to the same extent, do not have an effect on the position of equilibrium, but you do get to equilibrium faster

47
Q

3 types of catalysts

A

heterogenous catalysts
homogenous catalysts
autocatalysts

48
Q

heteorgenous catalysts

A

when the reactants and the catalyst are in different phases e.g in haber process the reactants are gases and catalyst, iron is a solid

49
Q

homogenous

A

when the reactants and the catalyst are in the same phase e.g potassium iodide soln (liquid) catalyses decomposition of hydrogen peroxided (liquid) into water and oxygen

50
Q

autocatalysts

A

when the catalyst is the product of the reaction

51
Q

catalysts in catalytic converters

A

platinum, palladium and rhodium

52
Q

reactions that occur in catalytic converters

A

conversion of harmful gases such as carbon monoxide and nitrogen monoxide to form carbon dioxide and nitrogen

53
Q

activation energy

A

the minimum amount of energy that colliding particles must have in order for a reaction to occur

54
Q

size of activation energy determines what?

A

the rate of the reaction

55
Q

can you increase or decrease activation energy for a reaction

A

no

56
Q

if activation energy is high

A

only small amount of molecules have it so reaction is slow

57
Q

what happens if you increase the temperature 2

A

increase in the kinetic energy of the molecules

greater proportion of molecules will have activation energy

58
Q

why is increase in kinetic energy not hugely significant?

A

the molecules will collide more often, but if they do not have energy the collisions will be ineffective

59
Q

2 theories for the mechanisms of catalysts

A

surface absorption theory

intermediate compound formation theory

60
Q

what does surface absorption theory explain

A

heterogenous catalysis

61
Q

according to surface absorption theory, if a solid catalyst is placed among gaseous reactants, what happens

A

the gases adsorb onto the surface of the catalyst

62
Q

surface absorption theory

advantages of gases adsorbing onto catalyst

A

increased concentration of the gases on the surface of the catalyst, more effective collisions happening

63
Q

surface absorption theory

what happens to the product

A

leaves the surface of the catalyst and allows more reactants to adsorb

64
Q

example of heterogenous catalysis

A

the haber process

65
Q

intermediate compound formation theory

2 points about the intermediate compound

A

forms very quickly and decomposes as soon as it is formed

66
Q

to get evidence for intermediate compound formation theory

A

potassium sodium tartrate is oxidised by hydrogen peroxide using cobalt (II) as a catalyst

67
Q

first few steps of experiment to get evidence for intermediate compound formation theory

A

potassium sodium tartrate dissolved in water, cobalt (II) ions added, hydrogen peroxide added

68
Q

colour of Co2+ ions

A

pink

69
Q

to get evidence for intermediate compound formation theory

colour when everything added

A

green

70
Q

to get evidence for intermediate compound formation theory

what is given ff

A

carbon dioxide and steam given off very vigorously

71
Q

to get evidence for intermediate compound formation theory

after a while when the reaction is finished

A

pink colour appears again, Co2+ not used up

72
Q

effect of catalysts on activation energy

A

when a catalyst is added to a reaction it provides an alternative route with a lower activation energy, more molecules will have this, rate increases

Chemistry (Tara) (50 decks)

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