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SYNOPTIC QUESTIONSA2 TOPIC 28
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QUESTIONSHEETS A2 LevelCHEMISTRY
26 marks
20 marks
29 marks
22 marks
25 marks
28 marks
18 marks
21 marks
25 marks
25 marks
27 marks
26 marks
25 marks
24 marks
28 marks
20 marks
27 marks
20 marks
26 marks
23 marks
20 marks
Involving acid-base equilibria, isomerism and volumetric
analysis
Involving oxidation-reduction, transition metals and
catalysis
Involving equilibria, energetics, bonding and volumetric
analysis
Involving reaction kinetics and applied organic chemistry
Involving titanium chemistry, chlor-alkali industry and
Born-Haber cycle
Involving energetics and Born-Haber cycle
Involving energy and free energy
Involving redox equilibria, volumetric analysis and laboratory
chemistry
Involving organic syntheses, reaction mechanisms and yield
calculation
Involving ammonia and nitric acid
Involving oxidation-reduction and group trends
Involving isomerism and pharmaceuticals
Involving fuels and chemical calculations
Involving azo dyes, theory of indicators and acid-base
equilibria
Involving reaction kinetics and aromatic chemistry
Involving sulphuric acid and organic reaction mechanisms
Involving polymers and volumetric analysis
Involving Group 7 chemistry, acid-base equilibria and volumetric
analysis
Involving structure of organic compounds, infrared spectroscopy
and isomerism
Involving pharmaceuticals and organic syntheses
Involving aluminium chemistry, mole calculations and reaction
mechanisms
Questionsheet
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-
A2 Level
SYNOPTIC QUESTION 1
TOTAL / 26
Acid-base equilibria (pH, [H+], buffers)Isomerism (optical)
Qualitative organic analysis (OH)Calculation (volumetric
analysis, formula
mass/composition)
In order to reduce tooth decay, it is recommended that the
intake of sugar-containing food and drink is reduced and alsothat
teeth and gums be cleaned regularly, especially after meals. After
eating, the pH level in the mouth can change fromthe normal level
of about 6.75 to around 4.5 due to the breakdown of sugars into
acids such as lactic acid (CH
3CHOHCOOH).
The pH value of about 4.5 may remain at this level in the mouth
for up to 20 minutes, during which time the tooth enamelis being
attacked and demineralised by the acids present. However,
hydrogencarbonate ions, HCO
3-, present in saliva,
introduce a buffering action and the pH value returns to normal
in approximately 1 to 2 hours. Chewing ‘sugar-free’ gumstimulates
the production of extra saliva and its use after meals, when
brushing is not possible, may help to reduce toothdecay by
returning the pH levels back to normal in a shorter time.
a) (i) Calculate the H+ ion concentration at pH 6.75 and at pH
4.5. [2]
(ii) Calculate the percentage increase in the H+ ion
concentration. [2]
(iii) Explain how the hydrogencarbonate ions act as a buffering
agent in the reduction of the H+ ionconcentration. [2]
b) Lactic acid (2-hydroxypropanoic acid) exhibits the property
of optical isomerism. Illustrate and explain theorigin of this
property by showing the structures of its two optical isomers.
[4]
c) One of the ingredients present in the ‘sugar-free’ gum is the
sweetener sorbitol, CH2OH.(CHOH)
4CH
2OH.
(i) Describe, with a suitable equation and the expected
observations, a simple test to show the presence of thehydroxyl
group, –OH, in a sample of solid sorbitol. [4]
(ii) What must be assumed about the sorbitol to make this a
reliable test? [1]
d) The disodium salt of EDTA (‘ethylenediaminetetra-acetic
acid’) forms stable complexes with many metal ions and canbe used
as a titrimetric reagent for estimating the concentrations of such
ions. 1.00 g of tooth enamel was dissolved inacid and made up to a
total volume of 250 cm3 with distilled water. A 25 cm3 sample of
this solution was then adjustedto a pH of 12 with a buffer solution
and titrated with a 0.1 mol dm-3 EDTA solution. After several
titrations, an averageof 9.45 cm3 of the EDTA solution were
required to reach the end point.Given that the reaction between
calcium ions and EDTA is represented by the equation:
Ca2+ + H2EDTA2- → Ca(EDTA)2- + 2H+
calculate the percentage by mass of calcium in tooth enamel.
[5]
e) Tooth enamel is reported to consist of 95% by mass of basic
calcium phosphate, of formula Ca10
(PO4)
6(OH)
2 .
Show, by calculation, whether or not your answer to d) is
consistent with this formula. [3]
f) From the formula given in e) suggest why tooth enamel
dissolves in acid [2]
g) The use of chewing gum is said to be dangerous to animals.
Suggest a reason [1]
enamel
gum
bacteriaOrganic acids e.g. CH
3CHOHCOOH*Sugar in food
TOPIC 28 Questionsheet 1
-
A2 Level
Redox equationsTransition metal properties
Isotope percentage and relative atomic massCarbon monoxide –
formation and treatment
SYNOPTIC QUESTION 2
TOPIC 28 Questionsheet 2
Smoke alarms and, to some extent, carbon monoxide detectors are
present in many homesand other places where people reside.
In addition, a small detector may sometimes be seen placed on a
wall close to a gas appliancesuch as a fire or water heater.
This type of detector contains a small area of orange coloured
crystals that darken whenexposed to carbon monoxide. The coloured
area contains orange palladium chloride crystalstogether with
copper(II) chloride. When exposed to carbon monoxide, the palladium
chlorideis changed into dark grey palladium metal:
CO + PdCl2.2H
2O → CO
2 + Pd + 2HCl + H
2O Equation 1
When the air is free of carbon monoxide, the palladium chloride
is regenerated by the copper(II) chloride:
Pd + 2CuCl2. 2H
2O → PdCl
2.2H
2O + 2Cu
Cl + 2H
2O Equation 2
The final stage is:
2Cu Cl
+ 2HCl + 3H
2O + ½O
2 → 2CuCl
2. 2H
2O Equation 3
a) Explain, with a suitable equation, how carbon monoxide is
released from appliances using natural gas. [2]
b) Why is it essential to be warned of the presence of carbon
monoxide in enclosed spaces, and what is theproperty of this gas
that make such detectors necessary? [2]
c) In terms of oxidation numbers, explain why the reaction
represented by Equation 1 is a redox reaction. [2]
d) Palladium is a ‘d-block element’. In terms of its electronic
structure, why can it also be described as a‘transition metal’, and
which one of its transition metal properties explains its behaviour
in Equations 1 & 2? [2]
e) What single overall equation can be formed from the
combination of Equations 1, 2 and 3? [2]
f) Palladium has six naturally occurring isotopes:
Relative mass of isotope 102 104 105 106 108 110
Abundance (%) 1.0 11.0 22.2 27.3 26.7 11.8
Calculate the relative atomic mass of palladium from this data.
[3]
g) (i) Name the technique used in obtaining the data in f)
[1]
(ii) This method of analysis is used in drugs-testing in sport,
space and medical research and environmentalmonitoring. What does
this suggest about this technique? [1]
-
A2 Level
SYNOPTIC QUESTION 2
TOPIC 28 Questionsheet 2 Continued
h) Carbon monoxide is emitted in the exhaust gases of cars but
the increasing use of catalytic converters resultsin about a 90%
reduction compared with cars not fitted with converters.
Hydrocarbons+ Air
Carbon monoxideCarbon dioxideNitrogenWaterNitrogen oxides
Carbon dioxideNitrogenWater
ignition 90%
NOx
COHC
N2 CO
2
H2O
ceramic monolith
NOx
HC CO
Al2O
3 particles impregnated
with metal catalysts
(By kind permission of The Open University: OpenLearn
http://openlearn.open.ac.uk/mod/resource/view.php?id=211955)
Typical urban emissions from Europeantechnology cars
Present European standards for passenger cars
Vehicle type CO / g km-1
27.0
2.0
2.2
Petrol without catalyst
Petrol with catalyst
Petrol
It has been estimated that 70% of the harmful emissions per
journey are released in the first 80 seconds when thecatalyst is
cold. A platinum catalyst starts working at 240 °C, while a
platinum-rhodium alloy starts at about 150 °C.
(i) Why is the catalyst described as heterogeneous?(ii) Suggest
why the catalyst is more effective when hot.(iii) Give reasons why
the catalyst is in the form of a very thin layer on a ceramic
support with a large surface area. [5]
TOTAL / 20
N2 CO
2
H2O
-
A2 Level
Kc - changes with temperatureBond energy calculations for
?HEffect of bonding on properties
Environmental problems from sulfur compounds
SYNOPTIC QUESTION 3
Crude oil contains a variable but significant percentage of
sulfur compounds. During the refining processes thesecompounds are
removed and converted into elemental sulfur. As much as 100 tonnes
of sulfur is recovered per day andutilised by other chemical
industries, for example in the production of sulfuric acid.
a) Calculate the quantity of sulfuric acid that could be
produced per day from this quantity of sulfur. [2]
b) As part of the recovery process, the sulfur compounds are
converted into hydrogen sulfide. This gas is then removedby passing
it, at low temperature, through an aqueous organic solvent (Solv),
which forms an unstable complex:
2 Solv(aq) + H2S(g) ¾ [Solv]
2.H
2S(aq)
(i) Write an expression for the equilibrium constant, Kc, for
this reaction and state its units. [2]
(ii) At low temperatures the value of Kc is large but decreases
as the temperature increases. State what this
indicates about the nature of ∆H for the reaction and give an
explanation. [4]
c) Sulfur is recovered from the hydrogen sulfide in a two-stage
process:
2H2S(g) + 3O
2(g) → 2H
2O(l) + 2SO
2(g) Equation 1
2H2S(g) + SO
2(g) → 2H
2O(l) + 3S(s) Equation 2
Given the following bond dissociation enthalpies (kJ mol-1):
H__S 364, O=O 498, H__O 464, S=O 497,
calculate ∆H values for both Equation 1 and Equation 2 and hence
state whether the recovery of sulfur fromhydrogen sulfide is
exothermic or endothermic. [5]
TOTAL / 29
TOPIC 28 Questionsheet 3
e) Small amounts of sulfur compounds do remain in liquid
hydrocarbon fuels and when burnt lead to the formation ofsulfur
dioxide. Catalytic converters reduce oxides of nitrogen back into
nitrogen and, at the same time, also reduce thesulfur dioxide into
hydrogen sulfide. This is often noticed as a ‘bad egg’ smell from
cold started engines. In what waysare these two sulfur compounds
damaging to both health and the environment? [3]
f) Outline an experiment that you could carry out in the
laboratory, using typical apparatus and reagents, to enableyou to
estimate the quantity of sulfur dioxide present in the atmosphere.
[4]
Quality of language [1]
d) Explain the differences in these values between these pairs
of compounds:
Compound Boiling point °C
Hydrogen sulfide -61
Water 100
Compound Bond angle
Hydrogen sulfide 92.2° (H-S-H)
Methane 109.3° (H-C-H)
[8]
-
A2 Level
Reaction order; rate equation/constantVegetable oils; level of
unsaturation & uses
Condensation polymers
SYNOPTIC QUESTION 4
Initial concentrations
[HCOOCH3] [OH-]
1 0.050 0.050 0.00034
2 0.050 0.100 0.00068
3 0.100 0.100 0.00136
Initial rate of reactionat 25 °C / mol dm-3 s-1
Experiment
a) The experimental study of the hydrolysis of the ester methyl
methanoate in the presence of sodium hydroxideproduced the
following data:
(i) From the data deduce the order of the reaction with respect
to both the methyl methanoate and the hydroxide ions.
(ii) Hence write a rate equation for the reaction.
(iii) Calculate the value of the rate constant. [5]
b) Natural vegetable oils and animal fats are esters which are
of economic importance because they can be used toproduce soap and
foodstuffs such as margarine. Vegetable oils are unsaturated
compounds, and the degree ofunsaturation is expressed by an iodine
value. Iodine adds across the double bond(s)
and the ‘iodine value’ is the mass of iodine required to fully
saturate 100 g of the oil. An ester of relative molecularmass 884,
present in olive oil, has an iodine value of 86.2.
(i) Calculate the number of double bonds present in one molecule
of the oil.
(ii) State the reagents and conditions required to convert the
oil into margarine and also into soap. [8]
c) Polyesters form the basis of many fabrics currently in
use.
(i) What is meant by the expression ‘condensation reaction’?
(ii) Use the above two formulae to draw one repeating unit of
the polymer.
(iii) Name or draw the structure of a functional group that
could be used instead of the carboxylic group (COOH)[4]
d) Over the last century fabric fibres have moved from natural
sources, such as wool, to semi-synthetic fibres, basedon cellulose
from wood pulp. The latter processes were complex and used
hazardous chemicals and were supersededby fully synthetic materials
from crude oil extracts.
Suggest the environmental and economic advantages and
disadvantages of returning to cellulose-based fibres as thelife
expectancy of known oil reserves reduces. [4]
Quality of language [1]TOTAL / 22
TOPIC 28 Questionsheet 4
C C C C
I I I I
Terylene is formed by a condensation reaction between the
following compounds
HOOC COOH and HO_(CH2)
2
_OH
(By kind permission of ASOS marketing
-
A2 Level
Titanium chemistry & extractionChlorine
disproportionation
The Born-Haber Cycle
SYNOPTIC QUESTION 5
a) Titanium metal is extracted from titanium(IV) oxide, TiO2.
This oxide is heated with coke in a stream of chlorine to
produce titanium(IV) chloride as a first stage in the process.
In the second stage, after separation and purificationby
distillation, the titanium(IV) chloride is reduced with either
magnesium or sodium, in vacuo, to produce the freemetal.
(i) Write balanced equations to represent the reactions taking
place in the two stages mentioned above.
(ii) Why is the reduction carried out in a vacuum?
(iii) Why is this extraction method used rather than the direct
reduction of the oxide by heating with coke?[4]
b) Chlorine for this process can be obtained by the electrolysis
of sodium chloride solution (‘brine’). Give an ionicequation for
the reaction of chlorine with water and explain why this is a
disproportionation reaction [3]
c) Titanium, especially when alloyed with other metals such as
aluminium, has high strength, low density and resistanceto
corrosion. In addition, it is the second most abundant transition
element and ninth most abundant of all theelements. State two
reasons why titanium has limited use despite its unique properties
and abundance. [2]
d) (i) Use the following data to construct a Born-Haber cycle
and then calculate the lattice enthalpy oftitanium(IV) oxide.
kJ mol-1
Enthalpy of atomisation of titanium 470Total ionisation energy
for Ti(g) → Ti4+(g) 8796Enthalpy of atomisation of oxygen 249Total
electron affinity for O(g) → O2-(g) 702Enthalpy of formation of
TiO
2(s) -940 [5]
(ii) With respect to the value of the lattice enthalpy of
titanium(IV) oxide, explain why it is an insolublesolid with low
reactivity. [2]
(iii) Titanium(IV) oxide and basic lead carbonate are both white
solids which can be used as a pigment in paints.Give one
contrasting property for these compounds that explains why titanium
dioxide has now replaced thelead compound for this use. [2]
e) Titanium(IV) chloride has a melting point of – 24 °C and a
boiling point of 136.5 °C. When used in conjunctionwith
triethylaluminum, it acts as a heterogeneous catalyst for the
production of high density poly(ethene).
TOTAL / 26
TOPIC 28 Questionsheet 5
(i) Which transition element property explains the catalytic
behaviour of titanium(IV) chloride?
(ii) What is understood by the term ‘heterogeneous
catalyst’?
(iii) Describe the bonding and structure of titanium(IV)
chloride.
(iv) When dissolved in concentrated hydrochloric acid,
titanium(IV) chloride forms an octahedral anion.Suggest a formula
for this product ion and name the types of bond within it
[7]
C C
HH
H H
n
-
A2 Level
Enthalpy of solutionBorn-Haber Cycle for solution
Experimental determination of ∆∆∆∆∆H
SYNOPTIC QUESTION 6
Athletes often use instant cold packs and hot packs as first-aid
devicesto treat injuries.
These devices operate by utilising the concept of enthalpy of
solution. Atypical pack consists of a plastic bag containing a dry
solid salt and apouch of water. Striking the pack causes the pouch
to break and thetemperature of the pack will either be raised or
lowered, depending onwhether the enthalpy of solution of the salt
is negative or positive.
Generally, calcium chloride or magnesium sulfate is used in hot
packs,and ammonium nitrate in cold packs.
a) Define ‘enthalpy of solution’. [3]
b) Draw a Born-Haber cycle for the dissolving of calcium
chloride and use it to show the connection betweenthe enthalpy of
solution of a salt, the hydration enthalpies of its ions, and the
lattice enthalpy of the salt. [5]
c) Explain why the enthalpy of solution for calcium chloride is
negative while that for ammonium nitrateis positive. [2]
d) Show, by calculation, that the temperature rise for 13 g
calcium chloride when added to 100 cm3 wateris consistent with the
value quoted in the extract above. (Assume that the specific heat
capacity of waterand calcium chloride solution is 4.18 J g-1 K-1.)
[4]
e) Outline an experiment, using standard laboratory apparatus,
to determine the enthalpy of solution of ammonium nitrate.What
assumptions are made in calculating the result? State the most
likely sources of error in the experiment and howthey might be
minimised. [13]
Quality of language [1]
TOTAL / 28
TOPIC 28 Questionsheet 6
Instant Cold and Hot Packs
The reactions are:
CaCl2(s) + aq → Ca2+(aq) + 2Cl-(aq) ∆H
soln= -82.8 kJ mol-1
NH4NO
3(s) + aq → NH
4+(aq) + NO
3-(aq) ∆H
soln= +26.2 kJ mol-1
Experiments show that the addition of 13 g calcium chloride to
100 cm3 water raises the temperature from 20 oCto 40 oC. Similarly,
when 30 g ammonium chloride is dissolved in 100 cm3 water at 20 oC
the temperature will belowered to 0 oC. A typical cold pack works
for approximately 20 minutes.
Adapted from: Instant Cold and Hot Packs, published in
‘Chemistry’ 4th Edition, by Raymond Chang.
(By kind permission of First Aid Warehouse)
-
A2 Level
Entropy and free energy
SYNOPTIC QUESTION 7
TOTAL / 18
TOPIC 28 Questionsheet 7
a) (i) Use these values for standard entropy (J K-1mol-1) :
HNO
3(l) = 156 ; O
2(g) = 205 ; H
2O(l) = 70
to calculate the standard entropy for nitrogen dioxide given
that the standard entropy change for the reaction :
4 HNO3(l) → 2 H
2O(l) + 4NO
2(g) + O
2(g) is +919 J K-1mol-1. [4]
(ii) Comment on the sign and magnitude of the reaction entropy
change. [2]
b) (i) Give two examples of types of change or chemical
situation where this relationship applies:
∆Sê = ∆Hê T [2]
(ii) Why does this relationship apply to these changes and not
to a chemical reaction? [2]
c) For the reaction:
Fe2O
3(s) + 3H
2(g) → 2Fe(s) + 3H
2O(g)
the standard enthalpy change = + 95 kJ mol-1 and the standard
enthalpiesfor each substance are (J K-1mol-1):
Fe2O
3(s) 90 ; H
2(g) 131 ; Fe(s) 27 ; H
2O(g) 189
(i) Calculate the standard entropy change for the reaction
[2]
(ii) Estimate the temperature at which this reaction becomes
possible. [3]
d) Match up these standard entropy values (J K-1mol-1) with the
substances in the table :
51 72 95 187 230
Ethane gas
Solid sodium chloride
Hydrogen chloride gas
Sodium metal
Solid ammonium chloride
[3]
-
A2 Level
Cell reactions and S.E.PVolumetric analysis
Organic practical techniques
SYNOPTIC QUESTION 8
a) A common example of a disposable alkaline battery employs the
two half-equations:
ZnO(s) + H2O(l) + 2e- ¾ Zn(s) + 2OH-(aq) Eê = -1.25 volts
2MnO2(s) + H
2O(l) + 2e- ¾ Mn
2O
3(s) + 2OH-(aq) Eê = +x volts
(i) Combine these two half-equations to produce an overall
equation for the reaction.
(ii) If the cell potential is +1.54 volts, what is the value of
x for the potential of the second half-equation?
(iii) State and explain which reaction takes place at the
positive pole of the cell.
(iv) What are the oxidation states of manganese in the two
manganese oxides shown in the secondhalf-equation? [8]
b) Manganese occurs as MnO2 in the mineral pyrolusite. A 2.00 g
sample of this mineral was dissolved in acid and the
manganese content converted into manganate(VII) ions. The
manganate(VII) ions were extracted from the reactionmixture and
transferred to a 250 cm3 volumetric flask and made up to the mark
with distilled water. 25 cm3 of thissolution were removed by
pipette and added to a conical flask containing 25 cm3 of 0.10 mol
dm-3 Fe2+ solution andexcess dilute sulfuric acid.The excess Fe2+
in this reaction mixture was back titrated with 0.02 mol dm-3
potassium manganate(VII) solution. Afterseveral repetitions, the
average volume of 0.02 mol dm-3 potassium manganate(VII) solution
required was 7.00 cm3.
MnO4
-(aq) + 8H+(aq) + 5e- → Mn2+(aq) + 4H2O(l)
Fe2+(aq) → Fe3+(aq) + e-
Use this data to find the percentage of manganese in the 2.00 g
sample by calculating the following.
(i) Moles of MnO4
-(aq) in 7.00 cm3 of 0.02 M potassium manganate(VII)
solution
(ii) Moles of excess Fe2+(aq)
(iii) Hence, moles of Fe2+(aq) that reacted with the
manganate(VII) ions produced from the original sample
(iv) Moles of manganate(VII) ions produced from the original
sample
(v) Moles of manganese in the original sample
(vi) Mass of manganese in the original sample
(vii) Percentage of manganese in the original sample [8]
c) An alkaline solution of potassium manganate(VII) is useful as
a powerful oxidising agent in the field of organicchemistry; for
example, benzenecarboxylic acid can be formed by the oxidation of
methylbenzene. In practice, themethylbenzene and alkaline potassium
manganate(VII) are heated under reflux for some time and then
allowed tocool. After filtration, to remove insoluble residues, the
filtrate is treated with excess hydrochloric acid to release
theslightly soluble benzenecarboxylic acid from its soluble sodium
salt. The acid is then removed by filtration underreduced pressure
and purified by recrystallisation from hot water.
(i) Sketch and label a diagram of the apparatus that is used for
either carrying out the refluxing or filtrationunder reduced
pressure.
(ii) How would you check that the recrystallised
benzenecarboxylic acid was pure? [5]
TOTAL / 21
TOPIC 28 Questionsheet 8
-
A2 Level
Involving organic syntheses, reaction mechanisms and yield
calculation
SYNOPTIC QUESTION 9
j) 4-Aminobenzenecarboxylic acid occurs naturally in many plants
as a compound of folic acid. What environmentaland economic factors
should be considered when deciding whether to manufacture the
product from methylbenzene,which is derived from crude oil, or by
extraction from plant tissue?
[3]
CH3
NO2
COOH
NH2
Substance XStep 1 Step 2
Identify substance X in the above sequence of reactions, and
state the conditions and reagents required forStep 1 and Step 2.
[5]
TOTAL / 25
TOPIC 28 Questionsheet 9
a) Following the above procedure, 15 cm3 of methylbenzene
(density 0.87 g cm-3) produced 11.5 g of4-nitromethylbenzene.
Calculate the percentage yield. [3]
b) Explain, using a balanced equation, the function of the
sulfuric acid in this reaction. [3]
c) Name and outline the mechanism by which the conversion of
methylbenzene into 4-nitromethylbenzeneoccurs. [4]
d) Why is the temperature not allowed to rise above 15 oC when
the methylbenzene is being added? [1]
e) Why is the product washed with water and with aqueous sodium
carbonate? [1]
f) During the final distillation, why is an air condenser used
rather than a water cooled condenser? [2]
g) Suggest two further essential safety precautions that should
be taken when carrying out this reaction. [1]
h) Suggest two reasons why the yield is low. [2]
i) If two further synthetic steps are carried out, the
4-nitromethylbenzene can be converted into4-aminobenzenecarboxylic
acid.
Carefully read the following instructions for the preparation of
4-nitromethylbenzene.Carry out this experiment in a fume
cupboard.
Place concentrated nitric acid (14 cm3) into a flask and slowly
add concentratedsulfuric acid (18 cm3). During the addition, gently
swirl the flask and cool it under arunning cold water tap. When the
addition is complete, further cool the flask in abeaker of
ice-water until the temperature of its contents is below 10 oC. At
this stageadd methylbenzene (15 cm3) dropwise, ensuring that the
temperature does not riseabove 15 oC. Fit a reflux condenser to the
flask and place it in a beaker of water atroom temperature. Gently
swirl the flask and its contents for about 40 minutes.
Transfer the mixture to a separating funnel and leave to
settle.Remove and discardthe lower layer. Add 25 cm3 of water,
shake and then run off the lower layer. Repeatthis once more with
water, then with aqueous sodium carbonate (1 mol dm-3) andfinally
with water. Pour the organic layer into a small conical flask
containing a fewpieces of anhydrous calcium chloride. Stopper the
flask and leave for one hour.Decant the liquid into a distillation
flask fitted with an air condenser. Distil the liquidand collect
the fraction boiling between 236 – 240 oC.
organic layer
aqueous layer
-
A2 Level
The Haber ProcessChemical equilibrium
EquationsRedox and oxidation number
SYNOPTIC QUESTION 10
TOTAL / 25
TOPIC 28 Questionsheet 10
a) This is a flow diagram for The Haber Process. Give
values/identities for A – E:
Natural gas and water
Liquified air
A
B
Converter
C (atm)
D (oC)
E (catalyst)
Ammonia
[5]
b) Suggest the environmental considerations needed in both the
siting and running of the plant. [4]
c) Ammonia is converted to nitric acid in three stages.
Stage 1 Conversion to nitrogen oxide, by reaction with oxygen at
900 oC in the presence of a platinum-rhodiumcatalyst.
Stage 2 Reaction of nitrogen oxide with oxygen at 200 oC to give
nitrogen dioxide.
Stage 3 Formation of nitric acid by dissolving nitrogen dioxide
in water in the presence of oxygen.
(i) Write an equation for each of these three stages
(ii) Give the initial and final oxidation states for nitrogen
for each stage
(iii) In redox terms, what has happened to nitrogen in all these
reactions and why? [8]
d) Stage 1
(i) does not require heating once the process has started
[2]
(ii) operates at high temperature with a catalyst. [1]What do
these points suggest in each case?
e) The reaction in Stage 2 is found in which process and causes
what environmental problem? [2]
f) If Stage 1 was allowed to reach equilibrium, a closed system
would be needed. What does this mean? [1]
g) How does the use of a catalyst affect the position of
equilibrium and why? [2]
-
A2 Level
Redox reactions; half-equationsMolecular geometry
Group trendsVolumetric analysis
SYNOPTIC QUESTION 11
Arsenic is a toxic element and there are many cases of it being
used by murderers. It is regularly monitored in Europeanpublic
drinking water supplies. The maximum allowable concentration in
surface waters used for drinking waterabstraction is 0.01
milligrams per litre.
Modern analytical methods used in water quality assurance begin
with complete oxidation of arsenic in the sample,with sodium
persulfate and concentrated sulfuric acid, to form H
3AsO
4. This is then reduced in two stages; first, using
potassium iodide, tin(II) chloride and acid, to form HAsO2 and,
second, using aluminium powder and acid, to form
arsenic(III) hydride, AsH3.
a) Express the maximum allowable concentration of arsenic given
above in mol dm-3. [2]
b) What is the oxidation number of arsenic in each of the
following compounds?
(i) H3AsO
4
(ii) HAsO2
(iii) AsH3
[3]
c) Give half-equations for these aqueous reactions.
(i) AsH3 to H
3AsO
4[2]
(ii) Iodide ion to iodine [1]
d) (i) Construct an equation for AsH3 reacting with iodine to
form H
3AsO
4 and iodide ion. [2]
(ii) Calculate the volume of iodine solution containing 0.10 g
dm-3 needed to exactly react with 1 dm3 solution
originally containing 0.05g arsenic and treated as above.
[7]
(iii) State and explain which of the reactants in (i) is
oxidised [2]
e) Draw a labelled diagram to describe the geometry of the AsH3
molecule [2]
f) Explain why, in comparison to ammonia, AsH3
(i) is a weaker base [3]
(ii) has a smaller bond angle [3]
TOTAL / 27
TOPIC 28 Questionsheet 11
-
A2 Level
Types of isomerismPharmaceutical stereospecificity
SYNOPTIC QUESTION 12
c) What type of isomerism considers different arrangements in
space for the same molecular structure? [1]
d) Limonene is an essential oil found in citrus friut. Its
formula is as follows:
(i) Copy out this formula and mark on it the structural feature
which is responsible for the fact that limoneneexhibits optical
isomerism. [1]
(ii) Write down the formula of the compound which would be
formed if limonene were to be reacted with excesshydrogen in the
presence of a nickel catalyst. Explain whether or not this new
compound would exhibitoptical isomerism.
[3]
(iii) One optical isomer of limonene is the ingredient of lemons
which gives this fruit its characteristic taste.Another optical
isomer tastes of oranges. Suggest the reason for this difference in
taste.
[2]
e) Many commercially available drugs are optically active
materials with one or more chiral centres. Drugs fromnatural
sources are often single isomers but those synthesised in the
laboratory are usually racemic mixtures of bothisomers. With few
exceptions, these are marketed as racemic mixtures because of the
expense and difficulty ofseparating them. Some pairs of isomers may
have the same physiological activity, but others may be very
differentto the extent that one may be beneficial while the other
could have disastrous side effects.
(i) What steps should drug manufacturers take to ensure the
safety of their product before putting it into generaluse? [2]
(ii) In what way does a racemic mixture differ from each optical
form and why? [2]
CH3
CH2
CCH
3
TOTAL / 25
TOPIC 28 Questionsheet 12
a) Define the term isomerism. [2]
b) Consider these four compounds :
A : CH3COCH
2CH
3 B : CH
3CH
2CH
2CHO C : (CH
3)
2CHCHO D : CH
3CH=CHCH
3
(i) Name each compound [4]
(ii) Which pair are chain isomers? [1]
(iii) Give a pair that are functional group isomers. [1]
(iv) Which compound could exist as E-Z isomers? Draw a diagram
of each form, labeling them E or Z. [4]
(v) Give the structural formula and name of a chain isomer of D
[2]
-
A2 Level
Fuels & their depletionCalculations for fuel yield
SYNOPTIC QUESTION 13
The following table provides generalised information on oil
reserves and the rate of use in millions of tonnes from thelate
nineteen eighties.
a) If oil is produced at the rates shown, which region will run
out of oil first and after how many years? [3]
b) If that region did not export oil, how long would its
supplies last? [1]
c) Which region would run out of oil first if it only used its
own resources, and how long would this take? [2]
d) Calculate the date when the world would run out of oil if
these data are correct and the rates ofconsumption and production
are maintained. [4]
e) Give reasons why the answer you gave in d) is unlikely to be
realistic. [4]
Coal resources are more extensive than oil resources, and in
times of embargo certain countries have produced oilfrom coal. At
the beginning of the 20th century large quantities of coal were
processed. This resulted in one tonne ofcoal yielding 340 m3 of
coal gas as well as coke, tar, ammonia and sulfur.
f) (i) Suggest industrial applications for the products, other
than coal gas and tar, obtained by heating coal. [3]
(ii) The tar produced can be used in road surfacing. Which
fraction from crude oil processing is also used for thispurpose?
[1]
g) Composition of typical coal gas by volume:
Use the data above to calculate the energy produced from the
complete combustion of 1 m3 of coal gas. [3]
h) Renewable organic fuels are possible alternatives to
hydrocarbon fuels. Suggest two possible sources. [2]
i) Give two reasons why hydrogen fuel cells are an
environmentally advantageous alternative to hydrocarbon fuels
[2]
TOTAL / 25
TOPIC 28 Questionsheet 13
Region Total reserves Annual rate of Annual ratedomestic
consumption of production
Asia 6,000 650 300
Australasia 200 36 27
Middle East 90,000 150 800
Former USSR 8,000 400 500
Central Europe 200 70 15
Western Europe 2,000 650 250
West Africa 8,000 100 350
North Africa 5,500 800 450
South Africa 17,000 250 3500
Enthalpy of combustion / kJ mol-1
Hydrogen 50% - 285.8Methane 30% - 890.0Ethene 3% - 1411.0Carbon
monoxide 7% - 280.3Carbon dioxide, nitrogen and oxygen 10%
-
A2 Level
Azo-dyesIndicators
Acid-base equilibriaVolumetric analysis
SYNOPTIC QUESTION 14
(i) Why is the formation of the benzenediazonium chloride and
the subsequent coupling reaction carried out at atemperature below
10 oC?
(ii) Suggest the type of mechanism taking place in the above
reaction. [2]
b) Certain coloured indicators used in acid-base titrations can
also be prepared by diazonium coupling reactions, forexample:
TOTAL / 24
14
12
10
8
6
4
2
0
pH
0 10 20 30 40 50Volume of 0.1 mol dm-3 NaOH solution
A
B
C
TOPIC 28 Questionsheet 14
N
+
N Cl
-
+
OH N N
OH+ H + Cl
+
-
Benzenediazonium chloride Phenol 4-Hydroxyazobenzene (yellow
dyestuff)
N N
+
-
SO3
NaN(CH3)
2
Methyl orange
(i) Draw the structures of the two compounds which would have
been used to make this dye. [2]
(ii) Explain how an acid-base indicator functions, using the
Brønsted Lowry theory. [3]
(iii) Methyl orange changes colour in the pH range 3.1 – 4.4.
Explain why this indicator changes over a differentpH range to
others such as bromothymol blue (6.0 – 7.6). [4]
c) A 25 cm3 portion of a mixture of hydrochloric acid and a weak
monoprotic acid, when titrated against 0.1 mol dm-3
sodium hydroxide, produced the following pH curve:
(i) Write an equation for the reaction taking place between A
and B. [1]
(ii) Name a suitable indicator to detect when point B is reached
and state the colour change that would be observed. [2]
(iii) Use the data from the graph to calculate:I the
concentration of the hydrochloric acid;II the concentration of the
weak acid present in the mixture. [4]
(iv) Using your results from c) (iii), calculate the volumes of
1 mol dm-3 hydrochloric acid and 0.5 mol dm-3 weak acidrequired to
produce 1 dm3 of the mixture used in the titration. Describe how
these volumes would be measured,and how the 1 dm3 of mixture would
be prepared with them. [6]
a) The discovery of diazonium compounds and their ability to
couple with phenols led to the development of a wholenew range of
brightly coloured dyestuffs, for example:
-
A2 Level
Reactions of phenolsIndicator structuresReactions kinetics
SYNOPTIC QUESTION 15
TOTAL / 28
TOPIC 28 Questionsheet 15
a) At room temperature aqueous phenol reacts rapidly with
bromine water to form 2,4,6-tribromophenol.(i) Write an equation
for this reaction using structural formulae. [1]
(ii) What would be observed? [2]b) Methyl red, a water-soluble
azo dye:
changes colour in moderately concentrated acid. Suggest what
happens to the methyl red molecule to cause thischange of colour.
[3]
c) The kinetics of fairly slow reactions which produce bromine
as a product can be followed by a Clock Reaction,which uses the two
rapid reactions mentioned above. For example, the reaction between
bromate(V) ions andbromide ions in the presence of acid can be
studied:
BrO3
-(aq) + 5Br-(aq) + 6H+(aq) → 3Br2(aq) + 3H
2O(l) Equation 1
The general method involves the mixing of an aqueous solution of
bromate(V) ions with an aqueous solution of bromideions in the
presence of a small but precise amount of phenol. This mixture is
then added to a measured quantity ofdilute acid and methyl red
indicator, an the time taken for a colour change to occur is
recorded. Typical results fromfour separate experiments are
displayed below
(i) Inorganic reactions are usually very fast. Suggest why this
reaction (Equation 1) is not so. [1]
(ii) What would be observed as this reaction takes place?
[1]
(iii) Using the data supplied in the table, determine the order
of the reaction with respect to each of the three reactantsand
briefly explain your reasoning. [6]
(iv) Write a rate equation and give the overall order for the
reaction. [2]
(v) Deduce the units of the rate constant for this reaction.
[3]
(vi) Given that the total volume of the reaction mixture in each
experiment is 40 cm3, calculate the total number ofmoles of
bromate(V) ions present in Experiment 1. [1]
(vii) Calculate the number of moles of bromine released in
Experiment1. [1]
(viii)In each reaction flask there were 5 x 10-7 moles of phenol
present. How many moles of bromine would have beenproduced at the
time of the colour change? [1]
(ix) How does the relative magnitude of the answers from (vii)
and (viii) support the assertion that Equation 1represents a slow
reaction? [2]
(x) Outline how the experiment might be adapted to study the
effect of temperature rise on the rate of this reaction.[4]
N N COOH
(CH3)
2N
Experiment
1
2
3
4
Initial concentration ofBrO
3-(aq)/ mol dm-3
0.00150
0.00150
0.00075
0.00150
Initial concentration ofBr(aq)/ mol dm-3
0.00250
0.00125
0.00250
0.00250
Initial concentration ofH+(aq)/ mol dm-3
0.0300
0.0300
0.0300
0.0150
Relativeinitial rate
4
2
2
1
-
A2 Level
Substitution reactions of benzene
SYNOPTIC QUESTION 16
TOTAL / 20
TOPIC 28 Questionsheet 16
Consider this scheme showing the synthesis of compounds from
benzene:
BrBr NO2I II
a) Copy out and complete this table:
Reaction Reactant(s) with benzene Conditions
I
II
[5]
b) Both of the reactions I and II are electrophilic
substitutions. Explain what is meant by this term [2]
c) In reaction II
(i) Give the formula of the electrophile [1]
(ii) Give equations to show the formation of the electrophile
[3]
(iii) Name the product [1]
(iv) Give a mechanism for the reaction [2]
d) (i) Phenol undergoes the same reaction as in II by using
dilute nitric acid at room temperature. Explain anydifference in
the conditions between the two reactions. [3]
(ii) Phenol can be used as a starting material for the synthesis
of an azo-dye by reaction with a compoundprepared from the product
in II. Name the compound formed from the product in II and the
reactants used. [3]
-
A2 Level
Addition polymerizationPolymer propertiesVolumetric analysis
SYNOPTIC QUESTION 17
TOTAL / 27
a) Rubber is a naturally occurring polymer of the monomer
2-methylbuta-1,3-diene. The monomer undergoes
additionpolymerisation to form rubber.
(i) Draw the full structural formula of this monomer.
(ii) What is meant by the term addition polymerisation? [3]
b) The polymer formed is called ‘latex’.(i) The polymer has half
the level of total unsaturation that was in the constituent
monomers. Draw a section of
the polymer formed from two monomer molecules. [2]
(ii) It is very soft and easily compressed, but returns to its
original shape when the pressure is removed. Suggest,in terms of
its structure and with reference to entropy, chaos or disorder, why
latex exhibits this ability toreform its original shape. [5]
c) Latex, however, is too soft and sticky for many commercial
applications such as the manufacture of motor car tyresand is
strengthened and hardened by a process termed vulcanisation. This
involves treating the latex with sulfur athigh temperatures and
pressures.
(i) The sulfur molecule is a puckered eight-membered ring of
sulfur atoms:
Suggest why the rings are puckered rather than planar.
(ii) If the level of unsaturation in vulcanized rubber is
greatly reduced compared to latex, suggest how and why thesulfur
causes hardening. [6]
d) The amount of sulfur present in vulcanised rubber affects its
strength, so that the rubber used for elastic bands has asmall
percentage of sulfur, while that for motor car tyres has a higher
percentage.
A student determined the percentage by mass of sulfur in an
elastic band by the following experiment. A 1.00 gsample of the
rubber was heated in a glass tube in a stream of oxygen gas. The
resulting sulfur dioxide and othergases produced were bubbled
through 100 cm3 of 0.050 mol dm-3 iodine solution containing a
small amount of dilutehydrochloric acid. When the reaction was
complete, 25.0 cm3 samples of the iodine solution were titratedwith
0.100 mol dm-3 aqueous sodium thiosulfate in order to determine the
excess of iodine left in the solution. Afterrepeating the
titration, the average volume of sodium thiosulfate solution used
was 18.75 cm3.
Given the equations:
SO2(g) + I
2(aq) + 2H
2O(l) → H
2SO
4(aq) + 2HI(aq)
I2(aq) + 2S
2O
32-(aq) → 2I-(aq) + S
4O
62-(aq)
calculate the percentage by mass of sulfur in the sample of
rubber. [8]
e) Synthetic rubbers based on 2-chlorobuta-1,3-diene are
manufactured in large quantities. Motor car tyres typicallycontain
both natural and synthetic rubbers. Worn out tyres, when stored in
large dumps, occasionally catch fire andburn fiercely. Name three
substances (other than water vapour) formed in such a fire and
indicate the health orenvironmental problems they could cause.
[3]
TOPIC 28 Questionsheet 17
S SS
S
SS S
S
-
A2 Level
Redox processesAcid-base equilibriaVolumetric analysis
SYNOPTIC QUESTION 18
TOTAL / 20
a) Copy out and complete the following chemical equilibrium:
Trichlor
The introduction of chlorine gas for disinfecting swimming pool
water provided considerable health bonuses. Theformation of
chloric(I) acid when chlorine reacts with water is the key to the
disinfecting action of aqueous chlorine.Chloric(I) acid is an
oxidising agent, which attacks micro-organisms, especially
bacteria. However, there are severalsignificant problems associated
with the use of chlorine, and solid tablets of “Trichlor”,
trichloroisocyanuric acid, areoften preferred.Trichlor reacts with
water to produce the weak acid, chloric(I) acid, HOCl, which
dissociates into hydrogen ions andchlorate(I) ions. The latter are
less effective as a disinfectant than HOCl molecules, but the
degree of dissociation canbe controlled by adjusting the pH.
Maintaining an optimum pH of swimming pool water is essential, not
only toensure an adequate concentration of chloric(I) acid, but
also to avoid excessive amounts of chloric(I) acid which leadto the
oxidation of aqueous ammonia, formed by sweat and urine reacting
with the water. Ammonia becomes oxidised,first, to chloramine,
NH
2Cl, and then to gaseous nitrogen. If the concentration of the
chloric(I) acid is particularly
high, nitrogen trichloride will be formed and bathers will
suffer from stinging eyes.
b) Write an equation for the dissociation of chloric(I) acid in
aqueous solution. [1]
c) What type of reaction is represented by b)? [1]
d) Suggest the benefits of using Trichlor rather than chlorine.
[3]
e) Chlorine reacts with water to give an equilibrium mixture
containing hydrogen ions, chloride ions and molecules ofchloric(I)
acid. Write ionic half-equations for the conversion of chlorine in
aqueous solution to (i) chloride ions,and (ii) chloric(I) acid.
Combine these half-equations into a single ionic equation. What
type of reaction is this?
[4]
f) Considering your answer to e), predict how increasing the pH
and lowering the pH, separately, affect theconcentrations of
chlorine and chloric(I) acid.
[2]
g) The text makes it clear that a relatively high concentration
of chloric(I) acid is needed, but if it becomes too highthen too
much of the eye-stinging nitrogen trichloride is formed. In
practice, a balance is achieved by maintainingsimilar
concentrations of both chlorate(I) ions and chloric(I) acid. Given
the pK
a of chloric(I) acid = 7.43, calculate
the optimum pH value for the swimming pool water. [3]
h) Outline a method of estimating the concentration of
chloric(I) acid in aqueous solution. [4]
N
N N
O
Cl
O
O
ClCl
....H2O(l)(aq) +
N
N N
O
H
O
O
HH
(aq) + ...................
[2]
“Trichlor” isocyanuric acid
TOPIC 28 Questionsheet 18
-
A2 Level
Structure & reactions of natural organic compoundsInfrared
spectroscopy
IsomerismFunctional group tests
TOTAL / 26
SYNOPTIC QUESTION 19
Plants have been called the Earth’s chemical factories. Starting
with simple chemical species, they can biosynthesise themost
outstanding molecular structures. The huge diversity of the plant
kingdom is matched by the incredible diversity ofthe ‘natural
products’ particular plants produce. Different species vary, not
only in their shape and colour, but also withregard to their
‘specialist chemicals’.
One fundamental building block is the five-carbon isoprene unit,
which has a four-carbon chain with a branch at C2.
Isoprene unit ⎯CH2⎯C CH⎯CH
2⎯
Individual building blocks are assembled head to tail, as shown
in the structures of Vitamin A and 11-cis-retinal usingdotted
lines:
Vitamin A
CH3
CH3
H3C CH
3 CH3CH
2OH
Retinal
CH3
CH3
H3C CH
3
H3C
CHO
TOPIC 28 Questionsheet 19
⎯⎯
CH3
The orange pigment of carrots, called carotene, is
biosynthesised from isoprene units by carrots.
CH3
CH3
H3C CH
3 CH3
CH3
H3CCH
3
H3C
CH3
Carotene
This is broken down into vitamin A molecules. Vitamin A is used
by the human body chemistry to produce
11-cis-retinal.11-cis-Retinal occurs in the retina of the human eye
where images in one’s line of sight are focused. The retinacontains
tissue called ‘cones’ that detect light, and there are three types
of cones, one for red light, one for blue andanother for green.
a) (i) Suggest the type of reaction occurring in Stages 1 and 2.
Explain your suggestion with reference to thefunctional groups
present. [3]
(ii) Name the functional groups present in retinol and retinal.
[2](iii) Explain how the features of an infra-red spectrum arise
[3](iv) Suggest two distinctly different features of the infra-red
spectra of these two compounds. [2](v) Would you expect either of
these compounds to be optical isomers? Give an explanation for your
answer. [2](vi) Give the molecular structure of the product for the
complete reaction of retinol with hydrogen gas at room
temperature in the presence of a catalyst. What colour would you
expect the product to be and why? [3](vii) Suggest the identity of
the catalyst in (v) [1](viii) Estimate the enthalpy of
hydrogenation of the reaction, given that the enthalpy of
hydrogenation of ethene is -
120 kJ mol-1. [2](ix) Suggest how and why the experimental value
would differ from this figure. [4]
b) Fehlings Reagent could be used to chemically distinguish
between vitamin A and retinal.(i) Describe what would be observed
with each compound [2](ii) Explain any positive test results.
[2](iii) Name one other reagent that could be used to distinguish
between these two structures [1]
Carotene Stage 1 Vitamin A (Retinol) Stage 2 11-cis-Retinal
-
A2 Level
PharmaceuticalsOrganic syntheses
SYNOPTIC QUESTION 20
TOPIC 28 Questionsheet 20
Draw the structural formula of compound Y which undergoes
esterification to produce aspirin. [1]
f) Complete the following reaction using structural
formulae.
Y OOC
O CH3
O
OHC
O
2-Hydroxybenzenecarboxylic acid Methanol Oil of wintergreen
Water [2]
g) What type of reaction is represented in f)? [1]
h) Suggest a catalyst for this reaction. [1]
i) Both oil of wintergreen and aspirin are pain killers. Explain
why aspirin is taken orally and oil of wintergreen isrubbed on the
skin. [4]
++
TOTAL / 23
By great good fortune for many cancer sufferers, the tissue of
an ordinary looking flower, the rosy periwinkle, fromtropical
Madagasca, was investigated by organic chemists. Two previously
unknown compounds were discovered, basedon the unique compounds
biosynthesised by that plant.
Following many years of testing and development, two commercial
drugs were produced with annual sales now in excessof £100
million.
Every year many species of plants, which live only in tropical
regions, are becoming extinct because of logging andredevelopment
of the land. As a result of these changes, the opportunity is lost
for scientists to investigate the propertiesof the organic
compounds which are naturally biosynthesised by plants soon to
become extinct.
a) Suggest the important steps which a company must undertake
before a new drug can be marketed. [3]
b) Suggest reasons for a tropical country politician to regard
intensive logging as important for his community. [2]
c) Give reasons for and against a foreign company taking samples
of plants which produce pharmacologically activeorganic compounds
from a tropical country with a poor living standard and patenting
medicines from them. [4]
Quality of language [1]
d) By stripping the bark of the common European willow tree it
is possible to extract aspirin. The 200 million aspirintablets
consumed each year are actually manufactured from feedstocks
produced by oil refineries. What are theenvironmental benefits of
this route rather than extraction from willow bark? [4]
e)
Aspirin (2-ethanoyloxybenzenecarboxylic acid)
-
A2 Level
Mole/yield caclulationsAromatic mechanisms
SYNOPTIC QUESTION 21
TOPIC 28 Questionsheet 21
TOTAL / 20
a) Briefly outline the economic and environmental advantages of
recycling items manufactured from aluminium such assoft drink cans.
[2]
Some of the aluminium was removed from a drinks can and cleaned
to remove paint and lacquer. A part of the aluminiumwas used for a
laboratory experiment as follows. 2.70 g of the cleaned aluminium
was added to an excess of potassiumhydroxide solution. The gas
released was collected and its volume measured when the reaction
was complete. Dilutesulfuric acid was then added to the reaction
mixture. Initially a white precipitate was seen to form but this
quicklyredissolved when more of the acid was added. When the
resulting solution was allowed to crystallise, 34.1g of
‘potassiumalum’, K
2SO
4.Al
2(SO
4)
3.24H
2O, were recovered.
b) The ionic equation for the reaction of aluminium with
potassium hydroxide is:
2Al(s) + 2OH-(aq) + 10H2O(l) → 2[Al(OH)
4(H
2O)
2]-(aq) + 3H
2(g)
(i) Calculate the volume of hydrogen gas produced, assuming that
under these conditions 1 mole of gas has avolume of 24 dm3. [3]
(ii) Calculate the percentage yield of potassium alum obtained
in this experiment. [4]
(iii) State the geometry of the product ion in the original
reaction. [1]
c) The other part of the aluminium from the drinks can was used
to prepare anhydrous aluminium chloride. Give anequation for this
reaction [1]
d) The rest of the aluminium chloride was used in the
preparation of chlorobenzene from benzene and chlorine.(i) Give an
overall chemical equation for this reaction. [1]
(ii) What was the role of the aluminium chloride in this
reaction? [1]
(iii) What type of reaction was this? [1]
(iv) Give the mechanism of this reaction. [4]
(v) Suggest two reasons why the chlorine atom in chlorobenzene
is unreactive to alkali under normal conditions [2]