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Chemistry Standard level Paper3 March 2018 (morning)
Candidate session number
I
1 hour Instructions to candidates
Write your session number in the boxes above. Do not open this examination paper until instructed to do so. answer all questions. Section A: Section B: answer all of the questions from one of the options. Write your answers in the boxes provided. A calculator is required for this paper. A clean copy of the chemistry data booklet is required for this paper. The maximum mark for this examination paper is [35 marks]. Option
L
Questions
Option A - Materials
3-7
Option B - Biochemistry
8-10
Option C - Energy
11 -15
Option D - Medicinal chemistry
16-20
Section A Answer all questions. 1.
The absorption of infrared (IR) radiation by molecules in the atmosphere affects global temperatures. Graph of IR absorbances for oxygen and ozone molecules
I·
UV
100
+ +
�1
IR
Visible
�
02
0 0
50
0
0
0.1 0.3 0.5 0.7
1
5
Wavelength I 1 o-s m
10
20
15
[Source: adapted from 2007 Thomson Higher Education, www.acs.org]
(a)
Using the graph, state, giving your reasons, whether or not oxygen and ozone are greenhouse gases.
[2]
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1 111111 28EP03
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(Question 1 continued) (b)
The following data has been compiled for a range of molecules that may be found in the atmosphere.
Molecule
Integrated IR intensity* I km moi- 1
co 2
25.7
0
1
CCl4
443.7
0
1 400
CCl3 F
705.2
0.45
4 750
CCl2F 2
970. 1
0.51
10 900
CClF3
1199
0.50
14 400
GWP** over 100 years
Molecular dipole moment I Debyes
CF4 [Sources: "Identifying the Molecular Origin of Global Warming", Partha P Bera. Joseph S Francisco and Timothy J Lee. Published in J. Phys. Chem. A, Vol. 113, No. 45, 2009 and accessed from www.r744.com]
*Integrated IR intensity is a measure of the extent to which the molecule absorbs infrared radiation passing through the atmosphere. **GWP: The global warming potential (GWP) is a relative measure of the total contribution of the compound to global warming over the specified time period. It is compared to the same mass of C02 , which has a GWP of 1. (i)
[1J
Use the integrated IR intensity data in the table to estimate the value for CF4.
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Explain the increase in molecular dipole moment as one chlorine atom in CCl4 is replaced with fluorine to produce CCl3 F.
(ii)
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111 11111 28EP04
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I (Question 1 continued) (iii)
Outline the relationship between GWP over 100 years and integrated IR intensity for CCL4 , CCL3 F, CCl 2 F 2 and CCLF 3 .
[1]
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Examine whether there is a general relationship between integrated IR intensity and molecular dipole moment.
(iv)
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CCL2 F 2 and CCLF 3 were developed for use as refrigerants but are now being replaced by other chemicals. Comment on their use with reference to values in the table and other environmental concerns.
[2]
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2.
A student wished to determine the concentration of a solution of sodium hydroxide by titrating it against a 0.100mol dm-3 aqueous solution of hydrochloric acid. 4.00g of sodium hydroxide pellets were used to make 1.00dm3 aqueous solution. 20.0cm3 samples of the sodium hydroxide solution were titrated using bromothymol blue as the indicator. Outline, giving your reasons, how you would carefully prepare the 1.00dm3 aqueous solution from the 4.00g sodium hydroxide pellets.
(a )
[2]
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(b)
(i)
State the colour change of the indicator that the student would see during his titration using section 22 of the data booklet .
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The student added the acid too quickly. Outline, giving your reason, how this could have affected the calculated concentration.
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(This question continues on the following page)
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1 11111 1 I 28EP06
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I (Question 2 continued) (c)
Suggest why, despite preparing the solution and performing the titrations very carefully, widely different results were obtained.
[1)
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I Section B Answer all of the questions from one of the options. Option A - Materials 3.
Materials science involves understanding the properties of materials and applying those properties to desired structures.
(a)
Magnesium oxide, MgO, and silicon carbide, SiC, are examples of ceramic materials. State the name of the predominant type of bonding in each material.
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(b)
Predict the predominant type of bonding for a binary compound AB in which the electronegativity of both atoms is low. Use section 29 of the data booklet.
(1]
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A student wanted to determine the formula of indium sulfate. She applied an electrical current of 0.300A to an aqueous solution of indium sulfate for 9.00 x 103 s and found that 1.07 g of indium metal deposited on the cathode. (a)
Calculate the charge, in coulombs, passed during the electrolysis.
(1]
charge 0 (current I = J time t
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(Option A continues on the following page)
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Ill! 1111 I 32EP08
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I (Option A, question 4 continued) Calculate the amount, in mol, of electrons passed using section 2 of the data booklet.
(b)
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Calculate the mass of indium deposited by one mole of electrons.
[11
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Calculate the number of moles of electrons required to deposit one mole of indium. Relative atomic mass of indium, Ar= 114.82.
[11
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Deduce the charge on the indium ion and the formula of indium sulfate.
[11
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II Ill I 32EP09
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(Option A continued)
5.
Research has led to the discovery of new catalysts that are in high demand and used in many chemical industries. (a)
Explain, with reference to their structure, the great selectivity of zeolites as catalysts.
[2]
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Nanocatalysts play an essential role in the manufacture of industrial chemicals. Describe the high pressure carbon monoxide {HIPCO) method for the production of carbon nanotubes.
( i)
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Outline one benefit of using nanocatalysts compared to traditional catalysts in industry.
[1]
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1 1 1 111 I 32EP10
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I (Option A continued) 6.
Polymers are made up of repeating monomer units which can be manipulated in various ways to give structures with desired properties. (a)
(b)
(i)
Draw the structure of 2-methylpropene.
[1 J
(ii)
Deduce the repeating unit of poly(2-methylpropene).
[1]
[1 J
Deduce the percentage atom economy for polymerization of 2-methylpropene.
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Suggest why incomplete combustion of plastic, such as polyvinyl chloride, is common in industrial and house fires .
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(Option A continues on the following page)
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111111 I 32EP11
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I (Option A, question 6 continued) Phthalate plasticizers such as DEHP, shown below, are frequently used in polyvinyl chloride.
(ii)
0 With reference to bonding, suggest a reason why many adults have measurable levels of phthalates in their bodies.
[1J
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Liquid crystals have many applications. (a)
Outline how a lyotropic liquid crystal differs from a thermotropic liquid crystal.
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(Option A, question 7 continued) (b)
Explain the effect of increasing the temperature of a nematic liquid crystal on its directional order.
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1 111111 11 32EP13
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I Option B - Human biochemistry
5.
Granola bars are a source of dietary fibre. (a)
(b)
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When 1.13 g of a granola bar was combusted in a bomb calorimeter, the temperature of 500 cm3 of water increased from 18.5 °C to 28.0 °C. Calculate the energy value, in kJ per I 00 g, of Lhe granola bar to the correct number of significant figures.
[3J
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(i)
State what is meant by the term dietary fibre.
[I]
(ii)
State two health problems that can be associated with a diet that 1s low m dietary fibre.
[2}
111111 1 40EP08
(Option B continues on the following page)
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I (Option B conlinued) 6.
Lipids are a group of molecules which includes fats, fat-soluble vitamins and triglycerides. (a)
State two examples of saturated fatty acids using Table 34 of the Data Booklet.
[I}
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(b)
Iodine can be used to determine the degree of unsaturation in fatty acids. (i)
Deduce the chemical equation for the reaction of oleic acid with iodine.
[I}
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(ii)
Calculate the volume, in cm3 , of a I .00 mol dm- 3 iodine solution needed to react exactly with 1.00 g of oleic acid (molar mass = 282.52 g mor').
[2J
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(Option B continues on the following page)
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1111 Ill I 40EP09
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' (Option B, question 9 continued) (c)
The partial equation for the enzyme-catalysed hydrolysis of a triglyceride is represented below.
II HC-0-C-R
oII I HC-0-C-R 2
(i)
I
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3X + Y
3Hp
HC-0-C-R 2
Deduce the named functional groups present in the two products X and Y.
[2J
X: Y:
(ii)
(d)
Outline the factors which determine whether X obtained in part (i) will have a higher or lower melting point than oleic acid .
Suggest why fats have a higher energy value than carbohydrates.
[2}
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11111111 40EP10
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(Option B continues on the following page)
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(Option B, question 9 continued) (e)
The two fatty acids linoleic acid and linolenic acid both have the same number of carbon atoms. Compare the structures of the two acids. [2}
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(Option B continues on the.following page)
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I I 1 111 I 40EP11
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I (Option B continued) 7.
Vitamins are organic compounds needed in small amounts for normal metabolism in the body. Vitamins can be classified as water-soluble or fat-soluble. (a)
Vitamin 89 is water-soluble and is important in the repair of DNA. The structure of vitamin 89 is given below.
O
II
OH � /
O
C
I
C, /CH .,.... OH ... cH i', c / 'cH NH 2
HN
I
II
0
N�CH,
H N
�
H ,N�N
N
O
Suggest why this vitamin is water-soluble.
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[I}
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(Option B continues on the following page)
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11111111 40EP12
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I (Option B, question 10 continued) (b)
Vitamin A (retinol) is important for maintaining healthy skin. (i)
State one disease caused by a deficiency of vitamin A in the body. [l}
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(ii)
The livers of polar bears and seals contain a very large amount of vitamin A. Some early explorers in the Arctic died from consuming too many livers. Suggest an explanation for this even though males require at least 0.9 mg of the vitamin per day (females require at least 0.7mg per day).
[JJ
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End of Option B
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1111111 40EP13
Turn over _J
I Option C - Energy 11.
Chemical energy from redox reactions can be used as a portable source of electrical energy. A hybrid car uses a lithium ion battery in addition to gasoline as fuel. (a)
(i)
Calculate the specific energy of the lithium ion battery, in MJ kg- 1, when 80.0 kg of fuel in the battery releases 1.58 x 107 J. Use section 1 of the data booklet.
[1]
.......................................................................... .......................................................................... (ii)
The specific energy of gasoline is 46.0 MJ kg- 1. Suggest why gasoline may be considered a better energy source than the lithium ion battery based on your answer to part (a) (i).
[1]
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The energy density of gasoline is 34.3 MJ dm-3. Calculate the volume of gasoline, in dm3, that is equivalent to the energy in 80.0 kg of fuel in the lithium ion battery. Use section 1 of the data booklet.
[1)
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The efficiency of energy transfer by this lithium ion battery is four times greater than that of gasoline. Determine the distance, in km, the car can travel on the lithium ion battery power alone if the gasoline-powered car uses 1.00 dm3 gasoline to travel 32.0 km.
[1]
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(Option C continues on the following page)
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111111 I 32EP20
_J
I (Option C continued) 12.
Auto-ignition of hydrocarbon fuel in a car engine causes "knocking". The tendency of a fuel to knock depends on its molecular structure. (a)
Discuss how the octane number changes with the molecular structure of the alkanes.
( 2)
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Catalytic reforming and cracking reactions are used to produce more efficient fuels. Deduce the equation for the conversion of heptane to methylbenzene.
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Carbon dioxide and water vapour are greenhouse gases produced by the combustion of fossil fuels. (a)
Explain the effect of the increasing concentration of atmospheric carbon dioxide on the acidity of oceans.
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(Option C continues on the following page)
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I 111111Ill I 32EP21
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I (Option C, question 13 continued) (b)
Describe the changes that occur at the molecular level when atmospheric carbon dioxide gas absorbs infrared radiation emitted from the Earth's surface.
(i)
[2]
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(ii)
Other than changes to the acidity of oceans, suggest why the production of carbon dioxide is of greater concern than the production of water vapour.
[1]
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14.
Biofuels are renewable energy sources derived mainly from plants. (a)
State the equation for the complete transesterification of the triglyceride given below with methanol.
[2]
(Option C continues on the following page)
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111 11111 32EP22
_J ----
(Option C, question 14 continued) (b)
Outline why the fuel produced by the reaction in (a) is more suitable for use in diesel engines than vegetable oils.
( 1)
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Nuclear reactions transform one nuclide into another. Fission, splitting a large nucleus into two smaller nuclei, releases vast amounts of energy. (a)
Explain why fusion, combining two smaller nuclei into a larger nucleus, releases vast amounts of energy. Use section 36 of the data booklet.
(i)
[2]
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Outline one advantage of fusion as a source of energy .
(ii)
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(Option C continues on the following page)
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111 IU I 32EP23
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(Option C, question 15 continued) (b)
Radioactive phosphorus, (i)
33
P, has a half-life of 25.3 days.
Calculate 33 P decay constant '"A and state its unit. Use section 1 of the data booklet.
[1]
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(ii)
Determine the fraction of the 33P sample remaining after 101.2 days.
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[1]
End of Option C
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11111111 32EP24
_J ------ --
Option D- Medicinal chemistry 16.
Penicillin is an antibiotic which contains a beta-lactam ring. Its general structure is shown below.
R
H
"-c--N
II
(a)
(i )
Outline what is meant by the term "ring strain" .
[1]
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(b)
(ii)
On the diagram above, label with asterisk/s (*) the carbon atom/s that experience ring strain.
[1]
(i)
Some antibiotic-resistant bacteria produce a beta-lactamase enzyme which destroys penicillin activity. Suggest how adding clavulanic acid to penicillin enables the antibiotic to retain its activity.
[1 J
COOH H Ou
0
Clavulanic acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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(Option D continues on the following page)
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1 1 111 II 1 32EP25
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(Option D, question 16 continued) (ii)
Populations of antibiotic-resistant bacteria have increased significantly over the last 60 years . Outline why antibiotics such as penicillin should not be prescribed to people suffering from a viral infection.
[2]
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17.
----
Oseltamivir (Tamiflu) and zanamivir (Relenza) are both used as antivirals to help prevent the spread of the flu virus, but are administered by different methods . (a)
Zanamivir must be taken by inhalation, not orally. Deduce what this suggests about the bioavailability of zanamivir if taken orally.
[1]
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(b)
Oseltamivir does not possess the carboxyl group needed for activity until it is chemically changed in the body. Deduce the name of the functional group in oseltamivir which changes into a carboxyl group in the body. Use section 37 of the data booklet.
[1]
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(c)
The synthesis of oseltamivir is dependent on a supply of the precursor shikimic acid, which is available only in low yield from certain plants, notably Chinese star anise. State one alternative green chemistry source of shikimic acid .
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(Option D continues on the following page)
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Il 111 I 32EP26
[1]
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_J
(Option D continued) 18.
The mild analgesic aspirin can be prepared in the laboratory from salicylic acid.
Salicylic acid
Aspirin
After the reaction is complete, the product is isolated, recrystallized, tested for purity and the experimental yield is measured. A student's results in a single trial are as follows.
Initial salicylic acid Crude product Product after recrystallization
Mass I g ±0.001 1.552 1.398 1.124
Melting point I °C ±1 106-114 122-125
Literature melting point data: aspirin = 138-140 °C (a)
(b)
Determine the percentage experimental yield of the product after recrystallization. The molar masses are as follows: M(salicylic acid)= 138.139 mol-1 , M(aspirin)= 180.17g mor 1 . (You do not need to process the uncertainties in the calculation.)
[ 2]
Suggest why isolation of the crude product involved the addition of ice-cold water.
[ 1]
(Option D continues on the following page)
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1 1 1111 1 32EP27
Turn over _J
I (Option D, question 18 continued)
(c)
Justify the conclusion that recrystallization increased the purity of the product, by reference to two differences between the melting point data of the crude and recrystallized products .
[2)
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State why aspirin is described as a mild analgesic with reference to its site of action.
[1 J
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19.
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Excess stomach acid leads to medical conditions that affect many people worldwide. These conditions can be treated with several types of medical drugs. (a)
..
Ranitidine (Zantac) is a drug that inhibits stomach acid production. Outline why the development of this drug was based on a detailed knowledge of the structure of histamine, shown below.
[1]
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(Option D continues on the following page)
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1 1 111 1 Ill 32EP28
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I (Option D, question 19 continued) (b)
Two other drugs, omeprazole (Prilosec) and esomeprazole (Nexium), directly prevent the release of acid into the stomach. Identify the site of action in the body.
[1]
(c)
A different approach to treating excess stomach acid is to neutralize it with antacids. Formulate an equation that shows the action of an antacid that can neutralize + three moles of hydrogen ions, H , per mole of antacid.
[1]
(Option D continues on the following page)
1111111111 32EP29
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I (Option D continued) 20.
Methadone, a synthetic opioid, binds to opioid receptors in the brain.
Methadone (a)
0
Compare and contrast the functional groups present in methadone and diamorphine (heroin), giving their names. Use section 37 of the data booklet.
[2]
One similarity:
One difference:
(b)
Methadone is sometimes used to help reduce withdrawal symptoms in the treatment of heroin addiction. Outline one withdrawal symptom that an addict may experience.
[1]
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End of Option D
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1111111 I 32EP30
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Candidate session number
I
1 hour Instructions to candidates
Write your session number in the boxes above. Do not open this examination paper until instructed to do so. answer all questions. Section A: Section B: answer all of the questions from one of the options. Write your answers in the boxes provided. A calculator is required for this paper. A clean copy of the chemistry data booklet is required for this paper. The maximum mark for this examination paper is [35 marks]. Option
L
Questions
Option A - Materials
3-7
Option B - Biochemistry
8-10
Option C - Energy
11 -15
Option D - Medicinal chemistry
16-20
Section A Answer all questions. 1.
The absorption of infrared (IR) radiation by molecules in the atmosphere affects global temperatures. Graph of IR absorbances for oxygen and ozone molecules
I·
UV
100
+ +
�1
IR
Visible
�
02
0 0
50
0
0
0.1 0.3 0.5 0.7
1
5
Wavelength I 1 o-s m
10
20
15
[Source: adapted from 2007 Thomson Higher Education, www.acs.org]
(a)
Using the graph, state, giving your reasons, whether or not oxygen and ozone are greenhouse gases.
[2]
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1 111111 28EP03
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(Question 1 continued) (b)
The following data has been compiled for a range of molecules that may be found in the atmosphere.
Molecule
Integrated IR intensity* I km moi- 1
co 2
25.7
0
1
CCl4
443.7
0
1 400
CCl3 F
705.2
0.45
4 750
CCl2F 2
970. 1
0.51
10 900
CClF3
1199
0.50
14 400
GWP** over 100 years
Molecular dipole moment I Debyes
CF4 [Sources: "Identifying the Molecular Origin of Global Warming", Partha P Bera. Joseph S Francisco and Timothy J Lee. Published in J. Phys. Chem. A, Vol. 113, No. 45, 2009 and accessed from www.r744.com]
*Integrated IR intensity is a measure of the extent to which the molecule absorbs infrared radiation passing through the atmosphere. **GWP: The global warming potential (GWP) is a relative measure of the total contribution of the compound to global warming over the specified time period. It is compared to the same mass of C02 , which has a GWP of 1. (i)
[1J
Use the integrated IR intensity data in the table to estimate the value for CF4.
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Explain the increase in molecular dipole moment as one chlorine atom in CCl4 is replaced with fluorine to produce CCl3 F.
(ii)
[2]
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111 11111 28EP04
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I (Question 1 continued) (iii)
Outline the relationship between GWP over 100 years and integrated IR intensity for CCL4 , CCL3 F, CCl 2 F 2 and CCLF 3 .
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Examine whether there is a general relationship between integrated IR intensity and molecular dipole moment.
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CCL2 F 2 and CCLF 3 were developed for use as refrigerants but are now being replaced by other chemicals. Comment on their use with reference to values in the table and other environmental concerns.
[2]
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Ill 11111 28EP05
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2.
A student wished to determine the concentration of a solution of sodium hydroxide by titrating it against a 0.100mol dm-3 aqueous solution of hydrochloric acid. 4.00g of sodium hydroxide pellets were used to make 1.00dm3 aqueous solution. 20.0cm3 samples of the sodium hydroxide solution were titrated using bromothymol blue as the indicator. Outline, giving your reasons, how you would carefully prepare the 1.00dm3 aqueous solution from the 4.00g sodium hydroxide pellets.
(a )
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(b)
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State the colour change of the indicator that the student would see during his titration using section 22 of the data booklet .
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The student added the acid too quickly. Outline, giving your reason, how this could have affected the calculated concentration.
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1 11111 1 I 28EP06
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I (Question 2 continued) (c)
Suggest why, despite preparing the solution and performing the titrations very carefully, widely different results were obtained.
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I Section B Answer all of the questions from one of the options. Option A - Materials 3.
Materials science involves understanding the properties of materials and applying those properties to desired structures.
(a)
Magnesium oxide, MgO, and silicon carbide, SiC, are examples of ceramic materials. State the name of the predominant type of bonding in each material.
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(b)
Predict the predominant type of bonding for a binary compound AB in which the electronegativity of both atoms is low. Use section 29 of the data booklet.
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A student wanted to determine the formula of indium sulfate. She applied an electrical current of 0.300A to an aqueous solution of indium sulfate for 9.00 x 103 s and found that 1.07 g of indium metal deposited on the cathode. (a)
Calculate the charge, in coulombs, passed during the electrolysis.
(1]
charge 0 (current I = J time t
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Ill! 1111 I 32EP08
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I (Option A, question 4 continued) Calculate the amount, in mol, of electrons passed using section 2 of the data booklet.
(b)
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Calculate the mass of indium deposited by one mole of electrons.
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Calculate the number of moles of electrons required to deposit one mole of indium. Relative atomic mass of indium, Ar= 114.82.
[11
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Deduce the charge on the indium ion and the formula of indium sulfate.
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(Option A continued)
5.
Research has led to the discovery of new catalysts that are in high demand and used in many chemical industries. (a)
Explain, with reference to their structure, the great selectivity of zeolites as catalysts.
[2]
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Nanocatalysts play an essential role in the manufacture of industrial chemicals. Describe the high pressure carbon monoxide {HIPCO) method for the production of carbon nanotubes.
( i)
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Outline one benefit of using nanocatalysts compared to traditional catalysts in industry.
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I (Option A continued) 6.
Polymers are made up of repeating monomer units which can be manipulated in various ways to give structures with desired properties. (a)
(b)
(i)
Draw the structure of 2-methylpropene.
[1 J
(ii)
Deduce the repeating unit of poly(2-methylpropene).
[1]
[1 J
Deduce the percentage atom economy for polymerization of 2-methylpropene.
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Suggest why incomplete combustion of plastic, such as polyvinyl chloride, is common in industrial and house fires .
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111111 I 32EP11
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I (Option A, question 6 continued) Phthalate plasticizers such as DEHP, shown below, are frequently used in polyvinyl chloride.
(ii)
0 With reference to bonding, suggest a reason why many adults have measurable levels of phthalates in their bodies.
[1J
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Liquid crystals have many applications. (a)
Outline how a lyotropic liquid crystal differs from a thermotropic liquid crystal.
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(Option A, question 7 continued) (b)
Explain the effect of increasing the temperature of a nematic liquid crystal on its directional order.
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1 111111 11 32EP13
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I Option B - Human biochemistry
5.
Granola bars are a source of dietary fibre. (a)
(b)
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When 1.13 g of a granola bar was combusted in a bomb calorimeter, the temperature of 500 cm3 of water increased from 18.5 °C to 28.0 °C. Calculate the energy value, in kJ per I 00 g, of Lhe granola bar to the correct number of significant figures.
[3J
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(i)
State what is meant by the term dietary fibre.
[I]
(ii)
State two health problems that can be associated with a diet that 1s low m dietary fibre.
[2}
111111 1 40EP08
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I (Option B conlinued) 6.
Lipids are a group of molecules which includes fats, fat-soluble vitamins and triglycerides. (a)
State two examples of saturated fatty acids using Table 34 of the Data Booklet.
[I}
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(b)
Iodine can be used to determine the degree of unsaturation in fatty acids. (i)
Deduce the chemical equation for the reaction of oleic acid with iodine.
[I}
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(ii)
Calculate the volume, in cm3 , of a I .00 mol dm- 3 iodine solution needed to react exactly with 1.00 g of oleic acid (molar mass = 282.52 g mor').
[2J
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(Option B continues on the following page)
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1111 Ill I 40EP09
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' (Option B, question 9 continued) (c)
The partial equation for the enzyme-catalysed hydrolysis of a triglyceride is represented below.
II HC-0-C-R
oII I HC-0-C-R 2
(i)
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3X + Y
3Hp
HC-0-C-R 2
Deduce the named functional groups present in the two products X and Y.
[2J
X: Y:
(ii)
(d)
Outline the factors which determine whether X obtained in part (i) will have a higher or lower melting point than oleic acid .
Suggest why fats have a higher energy value than carbohydrates.
[2}
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(Option B continues on the following page)
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(Option B, question 9 continued) (e)
The two fatty acids linoleic acid and linolenic acid both have the same number of carbon atoms. Compare the structures of the two acids. [2}
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(Option B continues on the.following page)
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I (Option B continued) 7.
Vitamins are organic compounds needed in small amounts for normal metabolism in the body. Vitamins can be classified as water-soluble or fat-soluble. (a)
Vitamin 89 is water-soluble and is important in the repair of DNA. The structure of vitamin 89 is given below.
O
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O
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C, /CH .,.... OH ... cH i', c / 'cH NH 2
HN
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Suggest why this vitamin is water-soluble.
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I (Option B, question 10 continued) (b)
Vitamin A (retinol) is important for maintaining healthy skin. (i)
State one disease caused by a deficiency of vitamin A in the body. [l}
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(ii)
The livers of polar bears and seals contain a very large amount of vitamin A. Some early explorers in the Arctic died from consuming too many livers. Suggest an explanation for this even though males require at least 0.9 mg of the vitamin per day (females require at least 0.7mg per day).
[JJ
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End of Option B
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1111111 40EP13
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I Option C - Energy 11.
Chemical energy from redox reactions can be used as a portable source of electrical energy. A hybrid car uses a lithium ion battery in addition to gasoline as fuel. (a)
(i)
Calculate the specific energy of the lithium ion battery, in MJ kg- 1, when 80.0 kg of fuel in the battery releases 1.58 x 107 J. Use section 1 of the data booklet.
[1]
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The specific energy of gasoline is 46.0 MJ kg- 1. Suggest why gasoline may be considered a better energy source than the lithium ion battery based on your answer to part (a) (i).
[1]
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The energy density of gasoline is 34.3 MJ dm-3. Calculate the volume of gasoline, in dm3, that is equivalent to the energy in 80.0 kg of fuel in the lithium ion battery. Use section 1 of the data booklet.
[1)
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The efficiency of energy transfer by this lithium ion battery is four times greater than that of gasoline. Determine the distance, in km, the car can travel on the lithium ion battery power alone if the gasoline-powered car uses 1.00 dm3 gasoline to travel 32.0 km.
[1]
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(Option C continues on the following page)
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111111 I 32EP20
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I (Option C continued) 12.
Auto-ignition of hydrocarbon fuel in a car engine causes "knocking". The tendency of a fuel to knock depends on its molecular structure. (a)
Discuss how the octane number changes with the molecular structure of the alkanes.
( 2)
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Catalytic reforming and cracking reactions are used to produce more efficient fuels. Deduce the equation for the conversion of heptane to methylbenzene.
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(1 J
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Carbon dioxide and water vapour are greenhouse gases produced by the combustion of fossil fuels. (a)
Explain the effect of the increasing concentration of atmospheric carbon dioxide on the acidity of oceans.
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(Option C continues on the following page)
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I 111111Ill I 32EP21
Turn over _J
I (Option C, question 13 continued) (b)
Describe the changes that occur at the molecular level when atmospheric carbon dioxide gas absorbs infrared radiation emitted from the Earth's surface.
(i)
[2]
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(ii)
Other than changes to the acidity of oceans, suggest why the production of carbon dioxide is of greater concern than the production of water vapour.
[1]
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- -- - -
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---- ·
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14.
Biofuels are renewable energy sources derived mainly from plants. (a)
State the equation for the complete transesterification of the triglyceride given below with methanol.
[2]
(Option C continues on the following page)
L
111 11111 32EP22
_J ----
(Option C, question 14 continued) (b)
Outline why the fuel produced by the reaction in (a) is more suitable for use in diesel engines than vegetable oils.
( 1)
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15.
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Nuclear reactions transform one nuclide into another. Fission, splitting a large nucleus into two smaller nuclei, releases vast amounts of energy. (a)
Explain why fusion, combining two smaller nuclei into a larger nucleus, releases vast amounts of energy. Use section 36 of the data booklet.
(i)
[2]
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Outline one advantage of fusion as a source of energy .
(ii)
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(Option C continues on the following page)
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111 IU I 32EP23
Turn over _J
(Option C, question 15 continued) (b)
Radioactive phosphorus, (i)
33
P, has a half-life of 25.3 days.
Calculate 33 P decay constant '"A and state its unit. Use section 1 of the data booklet.
[1]
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(ii)
Determine the fraction of the 33P sample remaining after 101.2 days.
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[1]
End of Option C
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11111111 32EP24
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Option D- Medicinal chemistry 16.
Penicillin is an antibiotic which contains a beta-lactam ring. Its general structure is shown below.
R
H
"-c--N
II
(a)
(i )
Outline what is meant by the term "ring strain" .
[1]
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(b)
(ii)
On the diagram above, label with asterisk/s (*) the carbon atom/s that experience ring strain.
[1]
(i)
Some antibiotic-resistant bacteria produce a beta-lactamase enzyme which destroys penicillin activity. Suggest how adding clavulanic acid to penicillin enables the antibiotic to retain its activity.
[1 J
COOH H Ou
0
Clavulanic acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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(Option D continues on the following page)
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1 1 111 II 1 32EP25
Turn over _J
(Option D, question 16 continued) (ii)
Populations of antibiotic-resistant bacteria have increased significantly over the last 60 years . Outline why antibiotics such as penicillin should not be prescribed to people suffering from a viral infection.
[2]
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17.
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Oseltamivir (Tamiflu) and zanamivir (Relenza) are both used as antivirals to help prevent the spread of the flu virus, but are administered by different methods . (a)
Zanamivir must be taken by inhalation, not orally. Deduce what this suggests about the bioavailability of zanamivir if taken orally.
[1]
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(b)
Oseltamivir does not possess the carboxyl group needed for activity until it is chemically changed in the body. Deduce the name of the functional group in oseltamivir which changes into a carboxyl group in the body. Use section 37 of the data booklet.
[1]
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(c)
The synthesis of oseltamivir is dependent on a supply of the precursor shikimic acid, which is available only in low yield from certain plants, notably Chinese star anise. State one alternative green chemistry source of shikimic acid .
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(Option D continues on the following page)
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Il 111 I 32EP26
[1]
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_J
(Option D continued) 18.
The mild analgesic aspirin can be prepared in the laboratory from salicylic acid.
Salicylic acid
Aspirin
After the reaction is complete, the product is isolated, recrystallized, tested for purity and the experimental yield is measured. A student's results in a single trial are as follows.
Initial salicylic acid Crude product Product after recrystallization
Mass I g ±0.001 1.552 1.398 1.124
Melting point I °C ±1 106-114 122-125
Literature melting point data: aspirin = 138-140 °C (a)
(b)
Determine the percentage experimental yield of the product after recrystallization. The molar masses are as follows: M(salicylic acid)= 138.139 mol-1 , M(aspirin)= 180.17g mor 1 . (You do not need to process the uncertainties in the calculation.)
[ 2]
Suggest why isolation of the crude product involved the addition of ice-cold water.
[ 1]
(Option D continues on the following page)
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1 1 1111 1 32EP27
Turn over _J
I (Option D, question 18 continued)
(c)
Justify the conclusion that recrystallization increased the purity of the product, by reference to two differences between the melting point data of the crude and recrystallized products .
[2)
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State why aspirin is described as a mild analgesic with reference to its site of action.
[1 J
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19.
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Excess stomach acid leads to medical conditions that affect many people worldwide. These conditions can be treated with several types of medical drugs. (a)
..
Ranitidine (Zantac) is a drug that inhibits stomach acid production. Outline why the development of this drug was based on a detailed knowledge of the structure of histamine, shown below.
[1]
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(Option D continues on the following page)
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1 1 111 1 Ill 32EP28
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I (Option D, question 19 continued) (b)
Two other drugs, omeprazole (Prilosec) and esomeprazole (Nexium), directly prevent the release of acid into the stomach. Identify the site of action in the body.
[1]
(c)
A different approach to treating excess stomach acid is to neutralize it with antacids. Formulate an equation that shows the action of an antacid that can neutralize + three moles of hydrogen ions, H , per mole of antacid.
[1]
(Option D continues on the following page)
1111111111 32EP29
Turn over _J
I (Option D continued) 20.
Methadone, a synthetic opioid, binds to opioid receptors in the brain.
Methadone (a)
0
Compare and contrast the functional groups present in methadone and diamorphine (heroin), giving their names. Use section 37 of the data booklet.
[2]
One similarity:
One difference:
(b)
Methadone is sometimes used to help reduce withdrawal symptoms in the treatment of heroin addiction. Outline one withdrawal symptom that an addict may experience.
[1]
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End of Option D
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1111111 I 32EP30
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