Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemistry🧪🔫 > 10) REACTION RATE & EQUILIBRIUM > Flashcards

10) REACTION RATE & EQUILIBRIUM Flashcards

1
Q

define rate of reaction

A

change in conc. of a reactant or product over a given period of time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the methods in measuring ROR ?

A

1) change in conc. of reactant + product
2) change in mass of R/P
3) change in gas vol. of P
4) change in colour of R/P

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

explain the procedure of measuring the change of conc. of R/P in a titration experiment

A

-small sample of reaction mixture extracted every 60 secs
-titrated against a standard conc of acidified KMn)4
-determines the conc. of Fe2+ ions produced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

describe the procedure of measuring the change in mass of R/P using balance

A

1) mass of flask + initial mass of acid + carbonate recorded with balance
2) stop clock started= flask left uncovered during reaction
3) mass is recorded at regular time intervals –> UNTIL CONSTANT MASS
4) flask covered with cotton wool/bung= gas escape when being measured

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

explain why we are able to measure the change in mass of R/P over a time?

A

-measure loss in mass over time using balance
-CO2 is produced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how can we measure the change in gas vol. of P ?

A

-ROR for decomposition of hydrogen peroxide
-gas syringe or measuring cylinder= determine vol. of oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are the 2 methods in which we can measure the change in gas vol. of P?

A

1) using measuring cylinder
2) using gas syringe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

describe the procedure of measuring the change in gas vol. of P using a measuring cylinder

A

1)hydrogen peroxide added to conical flask + bung placed
2)initial vol. of gas recorded
3) manganese oxide catalyst quickly added + bung replaced
4)stop clock started
5) vol. of O2 gas produced recorded at regular time intervals = UNTIL CONSTANT

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

describe the procedure of measuring change in gas vol. of P using a gas syringe?

A

1) hydrogen peroxide added to conical flask + bung placed
2) initial vol. of gas in gas syringe set at 0cm3
3) manganese oxide catalyst added + bung replaced
4) stop clock started
5)vol. of oxygen gas produced in gas syringe is recorded at regular time intervals= UNTIL CONSTANT

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

how do we measure the change in conc. of coloured R/P?

A

-colorimeter= measure the change in amount of light absorbed
-amount of light absorbed is proportional to conc.
-used to measure the change in conc.
-greater absorption= higher conc.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are some factors that affect the rate of chemical reaction?

A

-temp
-pressure
-conc.
-SA
-catalyst

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is the collision theory?

A

-for a reaction to occur 2 particles must collide successfully:
1) collide with correct orientation
2) collide with sufficient energy to overcome Ea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

explain how ⬆️ conc. ⬆️ ROR

A

-⬆️ number of particles in certain vol.
-closer together= ⬆️ frequency of collisions (with correct orientation + sufficient energy)
-ROR ⬆️

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

explain how ⬆️ pressure ⬆️ ROR

A

-⬆️ number of particles in certain vol.
-closer together =⬆️ frequency of collisions (with correct orientation +sufficient energy)
-ROR ⬆️

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

how do we calculate the ROR with a curved graph?

A

-draw a tangent line
- calculate gradient = change in y/ change in x

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is an example of biological catalysts?

A

digestive enzymes= produced by pancreas=⬆️ breakdown of food in gut

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what do catalytic converters do?

A

reduce toxic emissions in cars

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

how do catalytic converters work?

A

-contain platinum, rhodium + palladium catalysts
-converts toxic exhaust fumes into less harmful substances
-carbon monoxide + nitrogen monoxide react= carbon dioxide + nitrogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is the haber process?

A

-iron catalysts used in production of ammonia
-ammonia used in fertiliser manufacture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what do the iron catalysts do in the haber process?

A

⬆️ rate of ammonia production at lower temp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what happens during the contact process?

A

-vanadium oxide catalyst convert sulfur dioxide –> sulfur trioxide
-synthesise sulfuric acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what is a catalyst?

A

substance that provides an alternative route with a lower Ea without being used up

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is a heterogeneous catalsyt?

A

catalyst in a different phase/physical state from reactants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is a homogeneous catalyst?

A

catalyst in the same phase/physical state as reactants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what type of catalysts are catalytic convertors?

A

-heterogeneous
-platinum, rhodium + palladium= solid

26
Q

how do catalytic convertors work?

A

-catalysts supported on honeycomb mesh= large SA for reactions
-hot exhaust passed over catalyst= converted into less harmful substances

27
Q

what are some uses of catalysts in the industry?

A

-chemical reactions take place at lower temp= less fossil fuel burned= lower CO2 emission
-protect environment + reduce global warming
-reduced energy demand= reduced costs
-⬆️ ROR= ⬆️ energy efficiency
-improve air quality= catalytic convertors= reduce toxic emissions

28
Q

what is the modern focus on sustainability?

A

-industry operate processes with high atom economy
-few pollutants

29
Q

what does the Boltzmann distribution show?

A

spread of molecular energies in gases

30
Q

what are the features of a Boltzmann distribution graph?

A

-no mol. have 0 energy= curve start at origin
-area under curve=total # mol.
-no max energy= curve not meet the x-axis

31
Q

what are the labels of the Boltzmann distribution graph?

A

X= energy
Y= # of particles

32
Q

what does the Boltzmann distribution graph show about mol. past the Ea?

A

-only a small proportion
-with sufficient energy for effective collision

33
Q

what are the effect of increased temperature on the ROR?

A

-KE ⬆️
-particles move faster
-more frequent collisions
-⬆️ proportion of successful collisions

34
Q

what are the effects of increased temps on the Boltzmann distribution graph?

A

-curve FLATTENS
-peaks shifts to the RIGHT

35
Q

why does an increased temp cause an increase in ROR?

A

-more effective collisions
-more KE
-greater proportion of mol. with energy higher than Ea

36
Q

what are the effects of catalysts on the ROR ?

A

-provide a pathway with a lower Ea
-greater proportion of mol. have sufficient energy for effective collision

37
Q

what are the effects of catalysts on the Boltzmann distribution graph?

A

-greater proportion of mol. with sufficient energy
-Curve does NOT shift

38
Q

what are reversible reactions?

A

products can react to reform the original reactants

39
Q

what arrows are used to show a reversible reaction?

A

⇌

40
Q

what id a dynamic equilibrium?

A

-rate of forward reaction = rate of reverse reaction
-conc. of reactant + products does NOT change
-reactants + products constantly moving

41
Q

what is necessary for a reaction to remain in equilibrium?

A

closed system

42
Q

what is a closed system?

A

-isolated from surroundings
-temp, pressure + conc. of reactants + products are unaffected

43
Q

what does the position of the equilibrium show?

A

the extent of the reaction

44
Q

what can affect the position of the equilibrium?

A

-temp
-pressure
-conc.

45
Q

what happens to the conc. when the equilibrium shifts to the LEFT?

A

conc. of REACTANTS increases

46
Q

what happens to the conc. when the equilibrium shifts RIGHT?

A

conc. of PRODUCTS increases

47
Q

what is Le Chatelier’s principle?

A

if a change is made to a system in dynamic equilibrium, the position of the equilibrium shifts to counteract the change

48
Q

how does the equilibrium shift to counteract the change of INCREASE in conc.?

A

-equilibrium shift to the RIGHT
-reduce the effect of increase in conc. of reactant

49
Q

how does the equilibrium shift to counteract the change of DECREASE in conc.?

A

-equilibrium shift to the LEFT
–reduce the effect of a decrease in reactant

50
Q

how does the equilibrium shift to counteract the change of INCREASE in pressure?

A
  • equilibrium shift to side with less mol.
51
Q

how does the equilibrium shift to counteract the change of a DECREASE in pressure?

A

-equilibrium shift to side with more mol.

52
Q

how does the equilibrium shift to counteract the change of INCREASE in temp?

A

-move in ENDO

53
Q

how does the equilibrium shift to counteract the change of a DECREASE in temp?

A

-move in exo

54
Q

how does a catalyst affect the equilibrium?

A

-increase the rate of forward + backward equally
-reach equilibrium faster
-no effect on position

55
Q

what are the conditions needed for the max yield for ammonia?

A

-low temp= (=) shift right
-high pressure= (=) shift right

56
Q

what are some problems with using low temp + high pressure for a max yield of ammonia?

A

-low temp= slow rate
-high pressure= force mol. close together= increase conc. + ROR –> BUT= require strong container + large E = expensive + not safe

57
Q

what is the formula for Kc?

A

aA + bB ⇌ cC + dD

[A]^a X [B]^b

58
Q

what are the meanings of the Kc equation?

A
  • [ ] = concentration
  • a,b,c,d = balancing #
  • A,B,C,D = equilibrium conc.
59
Q

in the manufacture of ammonia at 400C the equilibrium conc. are;
- N2= 18.6 mol/dm3
- H2= 0.900 mol/dm3
- NH3= 1.50 mol/dm3

N2 +3H2 ⇌ 2NH3 calculate the value for Kc
A

1) Kc= [NH3 (g)]^2
———————-
[N2 (g)] x [H2 (g)]^3

2) (1.50)^2
—————
(18.6) x (0.900)^3

= 0.166

60
Q

The Boltzmann distribution can be used to show the effect of a change in temperature on the rate of a reaction.

· Draw a labelled Boltzmann distribution diagram.

· Explain the essential features of your diagram.

· Using your diagram, explain how an increase in temperature affects the rate of a reaction.

A

[sketch distribution to show axes labelled number/ fraction of molecules/atoms and energy]

-no molecules with no energy
-few very energetic molecules
-most have average amounts of energy
-area under curve is the number of molecules

[distribution at higher temperature shown on diagram hump lower than original ]

-Ea marked
-rate increases with an increase in temperature
-since more molecules have energy > Ea

61
Q

Explain why many industrial manufacturing processes use catalysts.

A

-enable reactions to occur with less waste
-less toxic solvents
-reaction scan happen at room temp
-saves energy
-reduce carbon emissions
-reactions occur with more specificity

Chemistry🧪🔫 (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions