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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
HOW PARTICLE SIZE CAN AFFECT REACTION RATE | how to calculate loss in mass
subtracting each mass from the initial mass before reaction started
26
HOW PARTICLE SIZE CAN AFFECT REACTION RATE | graph
loss in mass over time
27
HOW PARTICLE SIZE CAN AFFECT REACTION RATE | how to prove for particle size
graph results for different sizes of marble chips
28
the greater the concentration
the faster the reaction, generally
29
why is it faster for greater concentrations
a greater chance of reactants colliding with each other successfully
30
if temperature increased, and why
faster, more kinetic energy, more collisions
31
do catalysts always speed up reaction rates
no
32
catalyst that slows down the decomposition of hydrogen peroxide
glycerine
33
if a catalyst slows something down what is it called
a negative catalyst or inhibitor
34
TO STUDY THE EFFECTS ON THE REACTION OF (I) CHANGING CONCENTRATION (II) CHANGING TEMPERATURE, USING SODIUM THIOSULFATE AND HYDROCHLORIC ACID equation
Na2S2O3 + 2HCl -> s(↓) + 2NaCl + SO2
35
TO STUDY THE EFFECTS ON THE REACTION OF (I) CHANGING CONCENTRATION (II) CHANGING TEMPERATURE, USING SODIUM THIOSULFATE AND HYDROCHLORIC ACID what can you measure
the visibility of the cross drawn underneath
36
TO STUDY THE EFFECTS ON THE REACTION OF (I) CHANGING CONCENTRATION (II) CHANGING TEMPERATURE, USING SODIUM THIOSULFATE AND HYDROCHLORIC ACID first step
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
TO STUDY THE EFFECTS ON THE REACTION OF (I) CHANGING CONCENTRATION (II) CHANGING TEMPERATURE, USING SODIUM THIOSULFATE AND HYDROCHLORIC ACID step 2
known volume and molarity of HCl added and stop clock started
38
TO STUDY THE EFFECTS ON THE REACTION OF (I) CHANGING CONCENTRATION (II) CHANGING TEMPERATURE, USING SODIUM THIOSULFATE AND HYDROCHLORIC ACID step 3
swirl flask and stop clock when cross no longer visible
39
TO STUDY THE EFFECTS ON THE REACTION OF (I) CHANGING CONCENTRATION (II) CHANGING TEMPERATURE, USING SODIUM THIOSULFATE AND HYDROCHLORIC ACID how to examine concentrations
procedure repeated using other concentrations of sodium thiosulfate and times notes
40
TO STUDY THE EFFECTS ON THE REACTION OF (I) CHANGING CONCENTRATION (II) CHANGING TEMPERATURE, USING SODIUM THIOSULFATE AND HYDROCHLORIC ACID graph for concentrations
rate vs M
41
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
note temperature at the start and then repeat using various temperatures, heated by bunsen burne r
42
TO STUDY THE EFFECTS ON THE REACTION OF (I) CHANGING CONCENTRATION (II) CHANGING TEMPERATURE, USING SODIUM THIOSULFATE AND HYDROCHLORIC ACID graph for temperature
reaction vs absolute temperature
43
catalyst
a substance that alters the rate of a chemical reaction but is not used up during the reaction
44
4 general properties of catalysts
remain chemically unchanged specific reversible in their action catalyst poisons
45
may catalysts be physically changed by the end of a reaction?
yes, just not chemically
46
what does it mean to be reversible in their action
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
3 types of catalysts
heterogenous catalysts homogenous catalysts autocatalysts
48
heteorgenous catalysts
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
homogenous
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
autocatalysts
when the catalyst is the product of the reaction
51
catalysts in catalytic converters
platinum, palladium and rhodium
52
reactions that occur in catalytic converters
conversion of harmful gases such as carbon monoxide and nitrogen monoxide to form carbon dioxide and nitrogen
53
activation energy
the minimum amount of energy that colliding particles must have in order for a reaction to occur
54
size of activation energy determines what?
the rate of the reaction
55
can you increase or decrease activation energy for a reaction
no
56
if activation energy is high
only small amount of molecules have it so reaction is slow
57
what happens if you increase the temperature 2
increase in the kinetic energy of the molecules | greater proportion of molecules will have activation energy
58
why is increase in kinetic energy not hugely significant?
the molecules will collide more often, but if they do not have energy the collisions will be ineffective
59
2 theories for the mechanisms of catalysts
surface absorption theory | intermediate compound formation theory
60
what does surface absorption theory explain
heterogenous catalysis
61
according to surface absorption theory, if a solid catalyst is placed among gaseous reactants, what happens
the gases adsorb onto the surface of the catalyst
62
surface absorption theory | advantages of gases adsorbing onto catalyst
increased concentration of the gases on the surface of the catalyst, more effective collisions happening
63
surface absorption theory | what happens to the product
leaves the surface of the catalyst and allows more reactants to adsorb
64
example of heterogenous catalysis
the haber process
65
intermediate compound formation theory | 2 points about the intermediate compound
forms very quickly and decomposes as soon as it is formed
66
to get evidence for intermediate compound formation theory
potassium sodium tartrate is oxidised by hydrogen peroxide using cobalt (II) as a catalyst
67
first few steps of experiment to get evidence for intermediate compound formation theory
potassium sodium tartrate dissolved in water, cobalt (II) ions added, hydrogen peroxide added
68
colour of Co2+ ions
pink
69
to get evidence for intermediate compound formation theory | colour when everything added
green
70
to get evidence for intermediate compound formation theory | what is given ff
carbon dioxide and steam given off very vigorously
71
to get evidence for intermediate compound formation theory | after a while when the reaction is finished
pink colour appears again, Co2+ not used up
72
effect of catalysts on activation energy
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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