chemistry questionsheets a2 level questionsheets a2 level 26 marks 20 marks 29 marks 22 marks 25...

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SYNOPTIC QUESTIONS A2 TOPIC 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 QUESTIONSHEETS A2 Level CHEMISTRY 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 Curriculum Press – Licence Agreement: Paper copies of the A-Level Chemistry Questionsheets may be copied free of charge by teaching staff or students for use within their school, provided the Photocopy Masters have been purchased by their school. No part of these Questionsheets may be reproduced or transmitted, in any other form or by any other means, without the prior permission of the publisher. All rights are reserved. This license agreement is covered by the laws of England and Wales © Curriculum Press March 2008. The Curriculum Press • Bank House • 105 KIng Street • Wellington • Shropshire • TF1 1NU

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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

Curriculum Press – Licence Agreement:Paper copies of the A-Level Chemistry Questionsheets may be copied free of charge by teaching staff or students for use within their school, provided the Photocopy Masters have beenpurchased by their school. No part of these Questionsheets may be reproduced or transmitted, in any other form or by any other means, without the prior permission of the publisher. All rightsare reserved. This license agreement is covered by the laws of England and Wales © Curriculum Press March 2008.

The Curriculum Press • Bank House • 105 KIng Street • Wellington • Shropshire • TF1 1NU

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 NO2

I 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 CH3

CH2OH

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]