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FEB MOCK CHEM > CHEM PPQ > Flashcards

CHEM PPQ Flashcards

1
Q

This question is about magnesium, bromine and magnesium bromide.
Table 16.1 shows some physical properties of magnesium, bromine and magnesium bromide.

Substance Melting point / °C Electrical conductivity
Solid Liquid:
.Magnesium 711 Good Good
.Bromine −7 Poor Poor
.Magnesium bromide 650 Poor Good

Explain the physical properties shown in Table 16.1 using your knowledge of structure and
bonding

A

magnesium
.has a giant lattice structure and metallic bonding so has a high mp
.conducts as delocalised electrons can move

bromine:
.simple molecular
.london forces between molecules so low mp
.cant conduct as there is no mobile charge carriers

magnesium bromide:
.giant lattice structure + ionic bonding between opposietly charged ions= high mp
.in solution ions can move so can conduct electricity
.

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2
Q

This question is about some elements in Period 4 of the periodic table.
The table shows the melting point and electrical conductivity of two elements in Period 4.

Element Melting Point / °C Electrical conductivit:
Calcium 842 Good
Bromine –7 Poor
Use your knowledge of structure and bonding to explain the properties in the table.

A

Calcium:
.giant metallic lattice
.has metallic bonding = high mp
.has delocalised electrons that can move

bromine:
.simple molecular
.has london forces = low mp
.no free charge carriers

.metallic bonds are stronger than london forces

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3
Q

The reaction of barium with bromine is more vigorous than the reaction of calcium with
bromine.
Explain why [3]

A

.Ba has a greater atomic radius = nuclear attraction is less in Ba = easier to remove outer electrons in Ba

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4
Q

SiO2 and CO2 are oxides of Group 14 (Group 4) elements.
Solid SiO2 melts at 2156 °C. Solid CO2 melts at −56 °C.
Suggest the type of lattice structure in solid SiO2 and in solid CO2 and explain the difference in
melting points in terms of the types of force within each lattice structure.

A

.SiO2 has a gaint covalent lattice whereas CO2 has a simple molecular structure

.SiO2 has covalent bonds and CO2 has london forces
.covalent bonds are stronger than london forces

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5
Q

The reactivity of the Group 2 elements Mg–Ba increases down the group.

A

.atomic radius increases
.so nuclear attraction decreases
.less energy is needed to remove electron

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6
Q

B and C are ionic compounds of two different Group 1 elements.
The molar masses of B and C are both approximately 140 g mol−1.
A student dissolves B and C in water in separate test tubes and analyses the solutions.
The observations are shown below.

Test
Addition of HNO3(aq)
followed by BaCl2(aq)

B(aq:
bubbles
no change

C(aq)
no change
white precipitate

Use this information and the observations to identify the formulae of B and C.
Explain your reasoning.

A

.bubbling when HNO3 is added shows that B is a carbonate
.a white percipitate when BaCl2 is added shows that C is a sulfate

B = K2CO3
C = Na2SO4

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7
Q

First ionisation energies decrease down groups in the Periodic Table.
Explain this trend and the effect on the reactivity of groups containing metals.

A

.larger atomic radius
.nuclear charge increase outweighted by increased radius
.less electrostatic attraction to outer electrons = reactivity increases down groups

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8
Q

What is the name given to this repeating pattern of properties?

A

periodicity

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9
Q

The melting points of the Period 3 metals sodium and magnesium are shown below.

Metal Melting point / °C
sodium 98
magnesium 649

Explain the differences in the melting points of sodium and magnesium, using the model of
metallic bonding.

A

.magnesium has more outer electrons
.Mg ions have greater charge density
.Mg has greater attraction between ions and delocalised electrons

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10
Q

State how and explain why the attraction between nuclei and outermost electrons in gaseous
atoms varies across Period 3.

A

.attraction increases as num of protons increases
.as outer electrons are in the same shell

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11
Q

The Periodic Table is arranged in periods and groups.
Elements in the Periodic Table show a periodic trend in atomic radius.
State and explain the trend in atomic radius from Li to F.

A

.atomic radius decreases as nuclear charge increases
.and the electrons are in the same outer shell so there is a greater nuclear attraction on electrons

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12
Q

This question is about reactions and uses of the weak acids methanoic acid, HCOOH, and
ethanoic acid, CH3COOH.
A student adds magnesium metal to an aqueous solution of ethanoic acid, CH3COOH.
A redox reaction takes place.
Write the overall equation for this reaction and explain, in terms of oxidation numbers, which
element has been oxidised and which element has been reduced.

A

2CH3COOH + Mg —> (CH3COO)2Mg+ H2

Mg is oxidised from 0 to 2+
H is reduced from +1 to 0

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13
Q

The reaction of barium with bromine is more vigorous than the reaction of calcium with
bromine

A

.Ba has a larger atomic radius than Ca
.so nuclear attraction is less in Ba
.so ionisation energy for Ba is less

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14
Q

Outline 2 reaction routes for preparing a solution of Ba(OH)2 from barium in the laboratory.
Include relevant equations.

A

.add H2O to Ba
Ba+ H2O –> Ba(OH)2+ H2

.add O2 to Ba
2Ba + O2 –> 2BaO
.then add water
BaO + H2O –> Ba(OH)2

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15
Q

Write the equation for the reaction of strontium with water.

Describe two observations which would be different if the student had used calcium in
place of strontium.

A

Sr + 2H2O –> Sr(OH)2+ H2

.less vigourous bubbling
.dissolves slower

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16
Q

. Calcium nitride reacts with water to form a solution containing two alkaline compounds.
Write an equation for this reaction.

A

Ca3N2 + 6H2O –> 3Ca(OH)2+ 2NH3

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17
Q

This question is about Group 2 and Group 17 (7).
Barium chloride can be prepared from barium hydroxide in a neutralisation reaction.
Write the equation for this reaction. State symbols are not required.

A

Ba(OH)2 + HCl –> BaCl2 + H2O

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18
Q

The reactivity of the Group 2 elements Mg–Ba increases down the group.

A

.atomic radius increases
.nuclear attraction decreases
.ionisation energy decreases

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19
Q

Explain why the first ionisation energy of strontium is less than the first ionisation energy
of calcium.

A

.increased atomic radius
.increased electrons sheilding
.less electrostatic attraction

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20
Q

A chemist carries out reactions of barium and barium nitride, Ba3N2.
Reaction 1 Barium is reacted with water.
Reaction 2 Barium nitride is reacted with water, forming an alkaline solution and an alkaline
gas.
Reaction 3 Barium is reacted with an excess of oxygen at 500°C, forming barium peroxide,
BaO2.
i. Write equations for Reaction 1 and Reaction 2.

A

Ba + 2H2O -> Ba(OH)2+ H2

Ba3N2 + 6H2O -> 3Ba(OH)2 + 2NH3

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21
Q

A student adds a solution of bromine in an organic solvent to two test tubes.
The student adds aqueous sodium chloride to one test tube, and aqueous sodium iodide to the
other test tube.
The student shakes the mixtures, allows them to settle, and records the colour of the organic
layer in each mixture.

Sodium halide Colour of organic layer
Sodium chloride orange
Sodium iodide violet
Explain how the student’s results provide evidence for the trend in reactivity of the halogens down
group 17(7) and write an ionic equation for any reaction that takes place.
Use your chemical knowledge to explain the trend in reactivity

A

.orange contains bromine = no reaction
.violet contains iodine
Br2 + 2I- –> 2Br- + I2

.reactivity decreases down the group and gains electrons less easily
.due to greater atomic radius and more shielding so less nuclear attraction

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22
Q

. Chlorine is used in water treatment.
State one benefit and one risk of using chlorine in water treatment

A

.kills bacteria but is toxic

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23
Q

Explain the trend in boiling points of the halogens

A

.num of electrons increases
.more london forces
.more energy required to break intermolecular forces

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24
Q

Bromine is used to extract iodine from a solution containing iodide ions.
i. Write an ionic equation for the reaction.

A

Br2 + 2I- –> 2Br- + I2

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25
Q

Bromine disproportionates when it reacts with potassium hydroxide solution.
Suggest an equation for this reaction.

A

Br + K(OH)2 -> KBr + KBrO + H2O

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26
Q

Precipitation reactions can be used to distinguish between halide ions.
i. State the reagent needed for these precipitation reactions.

A

silver nitrate AgNO3

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27
Q

How would the appearance of the precipitates allow you to distinguish between chloride,
bromide and iodide ions?

A

.chloride is white
.bromide is cream
.iodide is yellow

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28
Q

This question is about properties of the halogens and halide ions.
Bromine can be extracted by bubbling chlorine gas through concentrated solutions containing
bromide ions.

Write an ionic equation for this reaction and state why this reaction takes place in terms
of reactivity of the halogens.

A

2Br- + Cl2 –> 2Cl- + Br2

chlorine is a stronger oxidisng agent

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29
Q

A student carries out test-tube experiments to prove the trend in reactivity of halogens.
The student is provided with the following solutions:
* bromine water
* aqueous iodine
* aqueous barium chloride
* aqueous magnesium bromide
* aqueous calcium iodide.
Chlorine gas and chlorine water are not available.
The student carries out the minimum number of test-tube experiments using these solutions in
the presence of cyclohexane (an organic solvent).
* State the solutions that need to be added together in order to prove the trend in reactivity
of the halogens, using the minimum number of test-tube experiments.
* Describe the colour seen in the organic solvent at the end of each test-tube experiment.
* Write an ionic equation for one reaction that takes place.

A

.BaCl2 + Br2 = yellow
.Cal2 + Br2 = lilac

.Br2 + 2I- –> I2 + 2Br-

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30
Q

. Chlorine reacts with aqueous sodium hydroxide to form bleach.
Write the equation and state the conditions for this reaction.

A

2NaOH + Cl2 –> NaCl + NaClO + H2O

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31
Q

This question is about nickel and its compounds.
A student is provided with samples of three nickel compounds.
One sample is nickel(II) bromide, another is nickel(II) sulfate and the third is nickel(II) carbonate.
The student doesn’t know which sample is which.
Describe the tests that the student could carry out to identify the anion (negative ion) in each
sample, and write equations for any reactions.

A

carbonate test:
.add HNO3
.fizzing = CO2 gas = carbonate
.2H+ + CO3
2– → CO2 + H2O

sulfate test:
.add BaCl2
.white percipitate = sulfate
.Ba2+ + SO4
2– → BaSO4

halogen test:
.add AgNO3
.white percipitate = chlorine
.cream percipitate = bromine
.yellow percipitate = iodine
.Ag+ + Br– → AgBr

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32
Q

You are supplied with a sample of ammonium bromide.
Describe simple tests that would identify the cation and anion present in ammonium bromide.
Include reagents, expected observations and relevant equations.

A

test for bromine:
.add silver nitrate and cream percipitate forms
.Ag+ + Br- –> AgBr

test for ammonia:
.heat with NaOH
.turns indicator paper blue
.NH4+ + OH- –> NH3 + H2O

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33
Q

Describe the use of aqueous barium chloride in qualitative analysis

A

.use to test for sulfates
.white percipitate forms

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34
Q

State the conditions of temperature and pressure used for standard enthalpy
measurements.

A

298K
100kPa

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35
Q

formula for calculating enthalpy change

A

q = mcΔT

q = heat energy(J)
m = mass of water/solution
c = 4.18

ΔH = q/moles

ΔH = enthalpy change(KJ)

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36
Q

At the end of the experiment, the student adds a few drops of aqueous sodium chloride
to the reaction mixture in the polystyrene cup to test whether all the aqueous silver
nitrate has reacted.
Explain how the results would show whether all the aqueous silver nitrate has reacted.
Include an equation with state symbols in your answer.

A

.white percipitate will form if there is remaining AgNO3

Ag+ + Cl- –> AgCl

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37
Q

5.10 tonnes of NH3 are converted into NO.
Calculate the energy released, in kJ, for this conversion.
Give your answer in standard form and to an appropriate number of significant figures

A

.find moles
.find the energy released per mole
.times both numbers together

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38
Q

The calculated value of ΔcH for hexane from this experiment is different from the data
book value.
Suggest two reasons for this difference

A

.heat is released into the surroundings
.incomplete combustion

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39
Q

Define standard enthalpy change of combustion

A

enthalpy change when one mole of a substance completely combusts with oxygen

298K 100kPa

40
Q

What is meant by the term average bond enthalpy

A

average enthalpy change when one mole of gaseous covalent bonds are broken

41
Q

What is meant by the term standard enthalpy change of formation?

A

when one mole of a compound is formed from its elements

42
Q

The graph shows that rate of reaction decreases over time.
Explain why, in terms of collision theory

A

.concentration decreases
.less frequent collisions

43
Q

Explain how a catalyst increases the rate of reaction

A

.lowers activiation energy by providing an alternate route
.a greater proportion of molecules have more energy than the activation energy

44
Q

Describe and explain the effect of increasing the pressure on the rate of this reaction.

A

.increases rate as molecules are closer together meaning that there are more colisions

45
Q

A student was asked to carry out an experiment to determine the initial rate of reaction of
zinc and hydrochloric acid.
The student plans to collect a total of about 72 cm3 of hydrogen at RTP and to use an excess of
zinc.
The student selects the following apparatus:

  • the apparatus shown in the diagram
  • 100 cm3measuring cylinder
  • stop clock
  • 2 decimal place balance
    Outline how the student could carry out the experiment and explain how the results could be
    processed graphically.
    Show all working in your calculations.
A

.measure mass of zinc using a 2dp balance
.measure vol of HCl using measuring cylinder
.mix zinc and acid in flask
.measure gas volume at timed intervals

.plot a graph of vol against time
.draw tangent a t = 0
.gradient of tangent = initial rate

46
Q

State an example of a catalyst used by the chemical industry and write the equation for the
reaction that is catalysed.

A

Ni
C2H4 + H2 –> C2H6

47
Q

State two ways that the use of catalysts helps chemical companies to make their processes more
sustainable and less harmful to the environment.

A

.lowers temp
.greater atom economy

48
Q

Outline a method that could be used to obtain the results that are plotted on the graph.
Your answer should include the apparatus required and the procedure for the experiment.

A

.flask
.balance
.stop clock

.time intervals every 10s

49
Q

Explain how le Chatelier’s principle can be used to predict the conditions of temperature
and pressure for a maximum equilibrium yield of ammonia

A

pressure:
.high pressure as ammonia has fewer gaseous moles

temp:
.low temp as the foward reaction is exothermic

50
Q

Calculate the numerical value for Kc for equilibrium 24.1 under these conditions.
Give your answer to an appropriate number of significant figures and in standard form.

A

kc = [C][D]/[A][B]

51
Q

Le Chatelier’ s principle can be used to predict how different conditions affect the equilibrium
position.
* Using le Chatelier’ s principle, show that a low temperature and a high pressure should
be used to obtain a maximum equilibrium yield of SO3.
* Explain why the actual conditions used in industry may be different from the conditions
needed for a maximum equilibrium yield.

A

TEMP:
forward reaction is exo

PRESSURE:
right side has fewer gaseous moles

INDUSTRIAL:
.high temp needed to increase rate
.high pressure uses alot of energy

52
Q

State le Chatelier’s principle

A

equilibrium shifts to minimise any change

53
Q

A closed system is required for dynamic equilibrium to be established.
State one other feature of this dynamic equilibrium

A

.rate of the foward reaction is equal to the rate of the reverse reaction
.conc dont change

54
Q

alcohol(H2SO4 + heat) –>

A

alkene

55
Q

Compounds A, B and C are saturated hydrocarbons.
The structures and boiling points of A, B and C are shown below.

  • Use the structures to explain what is meant by the term structural isomer.
  • Explain the trend in boiling points shown by A, B and C in the table.
A

.different structual formulae but same molecular formula
.C5H12

.bp decreases with branching as there are weaker London forces due to less contact and so less energy required to break the London forces

56
Q

. Compounds A, B and C all react with chlorine in the presence of ultraviolet radiation to form
organic compounds with the formula C5H11Cl.

A

radical subsitution

57
Q

Iodine monobromide, I–Br, is a polar molecule.
Heterolytic fission of the I–Br bond forms an electrophile.
State the meaning of the term electrophile and suggest the formula of the electrophile formed
from IBr.

A

.electron pair donor
I+

58
Q

Suggest the general formula for a carboxylic acid.

A

CnH2n+1COOH

59
Q

What is meant by the term homologous series?

A

group of compounds with the same functional group with each successive member differeing by CH2

60
Q

What does a curly arrow represent in mechanisms?

A

movement of an electron pair

61
Q

What is meant by the term nucleophile?

A

electron pair donor

62
Q

alkene(halogen) –>

halogenoalkane(KOH(aq)/warm) –>

alkene(steam and acid catalyst) =

A

halogenoalkane
alcohol
alcohol

63
Q

Explain what is meant by the term stereoisomers.

A

.same structual formula but different arrangement in space

64
Q

test for C=C functional group

A

.add bromine water
.becomes decolourised

65
Q

Under suitable conditions, butane, C4H10, reacts with chlorine by radical substitution. A mixture of
organic compounds is formed, including C4H9Cl , and compounds D and E.
i. Complete the table below to show the mechanism for the initiation and propagation
stages of the reaction of C4H10 with chlorine to form C4H9Cl .
In your equations, use molecular formulae and ‘dots‘ (·) with any radicals

A

initiation:
Cl2 –> 2Cl.
UV

propagation:
C4H10 + Cl. –> C4H9. + HCl
C4H9. + Cl2 –> C4H9Cl + Cl.

66
Q

At room temperature and pressure, the first four members of the alkanes are all gases but the
first four alcohols are all liquids.
Explain this difference in terms of intermolecular forces

A

.alcohols have hydrogen bonds and London forces whereas alkanes only have london forces

.hydrogen bond are stronger than london forces

67
Q

alkane + halogen –>

A

halogenoalkane + Hhalogen

e.g. HCl, HBr, HI

68
Q

Describe how a σ-bond forms.

A

direct overlap of orbitals between the bonding atoms

69
Q

alkene(H2 and nickel catalyst) –>

A

alkane

70
Q

State one advantage and one disadvantage of using combustion as a method for the
disposal of waste

A

.energy production
.formation of greenhouse gases

71
Q

After polymers have been used for packaging, the waste polymers need to be processed
to save resources, for example, by recycling.
Describe two other ways in which waste poly(propene) can be processed in a
sustainable way

A

.combustion for energy production
.use as and organic feedstock

72
Q

State and explain the features of a hex-2-ene molecule that lead to E and Z isomers.

A

.c=c restricts rotaton

.each carbon is bonding to two different groups

73
Q

Radical substitution produces a mixture of organic products.
Suggest two reasons why

A

.further subsitution
.subsitution at different points of the chain

74
Q

Describe how HCl is removed from the waste gases produced.

A

passed through a carbonate

75
Q

alcohol(K2Cr2O7/H2SO4 reflux) ->

A

carboyxlic acid

76
Q

alcohol(H2SO4/acid catalyst + heat) –>

A

alkene + H2O

77
Q

1-Bromobutane is an organic liquid with a boiling point of 102 °C.
A student prepares 1-bromobutane by reacting butan-1-ol with sulfuric acid and sodium bromide.
The student boils the mixture for one hour.
The equation is shown below.
CH3CH2CH2CH2OH + H+ + Br− → CH3CH2CH2CH2Br + H2O
The student obtains a reaction mixture containing an organic layer (density = 1.27 g cm−3) and an
aqueous layer (density = 1.00 g cm−3).
i. * Draw a labelled diagram to show how you would safely set up apparatus for the
preparation. Outline a method to obtain a pure sample of 1-bromobutane from the
reaction mixture

A

.draw a set up for reflux(round bottom flask, heat source, condenser)
.use separating funnel to separate organic and aqueous layers
.drying with MgSO4
.collect fraction distilling at 102C

78
Q

A student plans to carry out this oxidation using the apparatus shown in the diagram.
Give one reason why the apparatus is not suitable and describe a more suitable way of
carrying out this oxidation.

A

.its flammable
.heat under reflux or distillation

79
Q

Explain, with reference to a suitable chemical test, how compound J could be identified.
Your answer should not include spectroscopy

A

.add 2,4 DNP
.forms yellow percipitate
.take melting point of crystals
.compare to known values

80
Q

Explain what is meant by the term stereoisomers

A

.same structual formula
.different arrangements in space

81
Q

Outline the mechanism for the alkaline hydrolysis of (CH3)2CHCH2CH2Br.
The structure of (CH3)2CHCH2CH2Br has been provided.
Show curly arrows, relevant lone pairs and dipoles, and the products.

A

.C is delta positive and Br is delta negative
.arrow from OH- to C
.arrow from C-Br bond to Br

.OH where the Br was
.+ Br-

82
Q

The student decides to prepare alcohol A using the same method as in the part above but using
the chloroalkane (CH3)2CHCH2CH2Cl instead of the bromoalkane, (CH3)2CHCH2CH2Br.
State and explain how the rates of hydrolysis of the chloroalkane and the bromoalkane would
differ.

A

.Chloroalkane reaction would be slower
.as the C-Cl bonds are stronger than the C-Br bonds

83
Q

Construct an equation to show the formation of Cl * radicals from chlorotrifluoromethane

Ozone is broken down by Cl * radicals in a two-step process.
Write the equations for the two steps and the overall equation for this process

A

CF3Cl –> CF3. + Cl.

O3 + Cl. –> ClO. + O2
ClO. + O –> Cl.+ O2
O3 + O –> 2O2

84
Q

State two sources of nitrogen oxides in the stratosphere

A

lightning and aircrafts

85
Q

Write equations to show how nitrogen monoxide catalyses the breakdown of ozone.

A

NO. + O3 –> NO2 + O2
NO2. + O –> NO. + O2

86
Q

. Explain the following statements, using equations where appropriate.
o Life on Earth benefits from the presence of an ozone layer.
o The concentration of ozone is maintained in the ozone layer.
o Compound G produces radicals which catalyse the breakdown of ozone.

A

.ozone absorbs UV

O3 = O2 + O

CF3Cl —> Cl. + CF2Cl

Cl. + O3 –> ClO. + O2
ClO. + O –> Cl. + O2
O3 + O –> 2O2

87
Q

This question is about hex-1-ene, CH3CH2CH2CH2CH=CH2.
Hex-1-ene is a liquid with a boiling point of 63 °C and a density of 0.67 g cm–3.
Hex-1-ene can be prepared by refluxing hexan-1-ol (boiling point 157 °C) with an acid catalyst.
Hexan-1-ol is a liquid with a boiling point of 157 °C and a density of 0.82 g cm–3.
The equation is shown below.

After reflux, the resulting mixture contains unreacted hexan-1-ol, hex-1-ene and water.
The mixture is then purified.
The expected percentage yield of hex-1-ene from hexan-1-ol is 62.5%.
i. * A student plans to prepare 4.20 g of hex-1-ene by this method.
Calculate the mass of hexan-1-ol that the student should use and explain how you could
obtain pure hex-1-ene from the mixture obtained after reflux

A

.find moles of hexene
.find moles of hexan-1-ol needed n(hexene) x percentage yield of hexan-1-ol
.find mass needed

.use separating funnel
.dry with MgSO4
.Distillation

88
Q

A student hydrolyses a haloalkane, E, using the following method.

  • 0.0100 mol of haloalkane E is refluxed with excess NaOH(aq) to form a reaction mixture
    containing an organic product F.
  • The reaction mixture is neutralised with dilute nitric acid.
  • Excess AgNO3(aq) is added to the reaction mixture. 1.88 g of a precipitate G forms

Organic product, F, has a molar mass of 74.0 g mol−1 and has a chiral carbon atom.

Analyse the information to identify E, F and G

A

G = AgBr
.as Mr of percipitate = 188(1.88g/0.01 mol)
.188 - 107.9(mr of Ag) = 80.1 = mr of Br-

F = butan-2-ol

E = 2-bromobutane

89
Q

A student investigates the reaction between ethanoic acid, CH3COOH(l) and methanol,
CH3OH(l), in the presence of an acid catalyst. The equation is shown below.
CH3COOH(l) + CH3OH(l) ⇌ CH3COOCH3(l) + H2O(l)
The student carries out an experiment to determine the order of reaction with respect to
CH3COOH.
The student uses a large excess of CH3OH. The temperature is kept constant throughout the
experiment.
The student takes a sample from the mixture every 20 minutes, and then determines the
concentration of the ethanoic acid in each sample.
From the experimental results, the student plots the graph below.

i. Explain why the student uses a large excess of methanol in this experiment.

A

.it is zero order relative to the reaction

90
Q

Three students carry out a rates investigation on the reaction between bromine and propanone in the presence of
hydrochloric acid.
CH3COCH3(aq) + Br2(aq) → CH3COCH2Br(aq) + HBr(aq)
Each student investigates the effect of changing the concentration of one of the reactants whilst keeping the other
concentrations constant.
Their results are shown below.
Results of student 3

Experiment
[Br2(aq)] / mol dm−3

[CH3COCH3(aq)] /mol dm−3

[H+(aq)] / mol dm−3

Initial rate / 10−5 mol dm−3 s−1

1 0.004 1.60 0.20 1.25
2 0.004 1.60 0.40 2.50

Explain how the reaction orders can be determined from the students’ results, and determine the rate
equation and rate constant.

A

.Br2 is zero order
.CH3COCH3 is first order
.H+ is first order

.linear negative gradient = zero order
.straight line through 0,0 = first order
.[H+] x 2 and rate is x 2 = first order

k = rate/[CH3COCH3][H+]

91
Q

This question is about organic reactions.
Compound A is formed when ethanal is mixed with OH−(aq) ions, which act as a catalyst.
The balanced equation is shown in reaction 6.1 below.
i. Give the systematic name for compound A.

A

3-hydroxybutanal

92
Q

how to find activation energy using a lnk 1/T graph

A

Ea = -gradient x 8.314 (J mol-1)

93
Q

how to find pre-exponential factor on lnk 1/T graph

A

.find y intercept = ln A
.do e^intercept on calc

94
Q

how to find two-step mechanism for rate equations

A

RDS - use rate equation (balances for charge and num of atoms)

.use the product that is not in the equation to form the other products in the equation

95
Q
A

FEB MOCK CHEM (3 decks)

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