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Farr High School

NATIONAL 5 CHEMISTRY

Unit 2 Nature’s Chemistry

Exam Questions

(UPDATED MAY 2017)

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Homologous series 2006 I2 13MC

1. The above structural formulae represent A the same hydrocarbon B Different hydrocarbons C Isomers D Isotopes 1

2006 I2 14MC 2. The first three members of the alkanone series are: What is the general formula for this homologous series? A CnH2n-2O B CnH2nO C CnH2n-1O D CnH2n+2O 1

2006 I2 16MC 3. The structural formula for hydrocarbon X is Which of the following statements about hydrocarbon X is true? A X is named but-2-ene B X is a saturated hydrocarbon C X rapidly decolorises bromine solution D X belongs to a group of hydrocarbons with the general formula CnH2n+2 1

2008 I2 13MC 4. Which of the following compounds fits the general formula, CnH2n, and will rapidly decolourise bromine solution? A Cyclopentane B Cyclopentene C Pentane D Pentene

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2008 I2 12MC 5. The name of the above compound is A 1, 1–dimethylpropane B 2-ethylpropane C 2-methylbutane D 3-methylbutane. 1

2007 I2 10 MC 6. Which of the following compounds is an isomer of the one above? 1

2008 I2 14MC 7. Three members of the cycloalkane homologous series are:

The general formula for this homologous series is A CnH2n+2 B CnH2n C CnH2n–2 D CnH2n–4 . 1

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2008 I2 15MC 8. Which of the following molecules is an isomer of heptane?

2009 I2 15MC 9. Which of the following could be the molecular formula of a cycloalkane? A C7H10 B C7H12 C C7H14 D C7H16 1

2010 I2 10MC 10. 1 mole of a hydrocarbon burns completely in oxygen to produce 2 moles of carbon dioxide and 2 moles of water. The formula for the hydrocarbon is A C2H4 B C2H6 C C4H8 D C4H10. 1

2009 I2 16MC 11. The shortened structural formula for an organic compound is CH3CH(CH3)CH(OH)C(CH3)3. Which of the following is another way of representing this structure? 1

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2009 I2 12MC 12. Which of the following hydrocarbons does not belong to the same homologous series as the others? A CH4 B C3H8 C C4H10 D C6H12 1

2006 CRED 4 13. The structural formulae for some hydrocarbons are shown below. (a) Identify the hydrocarbon which could be used to make poly(butene). 1 (b) Identify the two hydrocarbons with the general formula CnH2n which do not react quickly with hydrogen. 1

2011 I2 8 14. Many different gases are found in car exhaust fumes. Some of these gases are produced by the combustion of petrol in car engines. The pie chart shows the gases present in the exhaust fumes of a car. What evidence in the pie chart shows that incomplete combustion of petrol has taken place? 1

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2013 I2 8 15. Crude oil is a mixture of hydrocarbons which can be separated into fractions by fractional distillation. Petrol contains the following molecule. Name this molecule. 1

2011 C 16 16. Heptane can be cracked as shown.

One of the reactions which takes place is:

The product C3H6 decolourises bromine solution quickly. Draw a structural formula for an isomer of C3H6, which would not decolourise bromine solution quickly. 1

2012 C 20 17. The monomer in superglue has the following structure. Bromine reacts with the monomer to produce a saturated compound. Draw the structural formula for this compound. 1

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2011 C 22 18.(a) Ethylthioethane belongs to a homologous series of compounds called

thioethers.

What is meant by a homologous series?

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(b) Ethylthioethane is formed when ethylthiol reacts with bromoethane as shown.

Draw the full structural formula for the thioether produced in the following reaction.

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(c)

Ethylthioethane can also be formed by the reaction of ethylthiol with ethene.

Suggest a name for the type of chemical reaction taking place.

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2007 I2 5 19. Thiols are organic compounds containing sulphur. Some thiols are listed in the table. (a) Ethanethiol is added to natural gas to give it a smell. Draw the full structural formula for ethanethiol. 1 (b) Suggest the name for thiol X. 1 (c) Thiols undergo complete combustion. thiols + oxygen → carbon dioxide + water + ……………………………… Complete the word equation for this reaction. 1

2007 I2 6 20. A student carried out an experiment to test different hydrocarbons for saturation. Her results are shown in the table. (a) Complete the table. 2 (b) Care had to be taken when using bromine solution. Give a safety precaution, other than eye protection, which should be taken when completing this test. 1 (c) Suggest a possible name for hydrocarbon B. 1

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2008 I2 5 21. Chlorofluorocarbons (CFCs) are a family of compounds which are highly effective as refrigerants and aerosol propellants. However, they are now known to damage the ozone layer. One example of a CFC molecule is shown. (a) What term is used to describe the shape of this molecule? 1 (b) Scientists have developed compounds to replace CFCs. The table shows information about the ratio of atoms in CCl2F2 and compounds used to replace it. (i) Draw a possible structure for Replacement 2. 1 (ii) Compared with CCl2F2, the replacement compounds contain less of which element? 1 (iii) From the table, what is the advantage of using the replacement molecules as refrigerants and aerosol propellants? 1

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2008 I2 7 22. Scientists have replaced oils in gloss paints with synthetic polyesters. This has improved the drying quality of the paint. The first step in the production of the synthetic polyester is shown. (a) What does the term synthetic mean? 1 (b) Copy out the triglyceride and circle an ester link. 1 (c) Name X. 1

2009 I2 6 23. The octane number of petrol is a measure of how efficiently it burns as a fuel. The higher the octane number, the more efficient the fuel. (a) What is a fuel? 1 (b) The octane numbers for some hydrocarbons are shown. (i) Predict the octane number for hexane. 1 (ii) State a relationship between the structure of the hydrocarbon and their efficiency as fuels. 1

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2009 I2 8 24. Alkynes are a homologous series of hydrocarbons which contain carbon to carbon triple bonds. Two members of this series are shown. (a) Name the first member of this series. 1 (b) Alkynes can be prepared by reacting a dibromoalkane with potassium hydroxide solution. (i) Draw a structural formula for the alkyne formed when the dibromoalkane shown below reacts with potassium hydroxide solution. 1 (ii) Suggest a reason why the dibromoalkane shown below does not form an alkyne when it is added to potassium hydroxide solution. 1

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2010 I2 5 25. The diagram below shows the apparatus used to ‘crack’ a hydrocarbon. (a) Describe how the bunsen burner is used to heat the apparatus. 1 (b) Explain why the delivery tube must be removed from the bromine solution before heating is stopped. 1 (c) (i) Name the catalyst that is used in this cracking reaction. 1 (ii) Catalysts speed up the rate of a reaction without being used up. State another reason for using a catalyst. 1 (d) One of the reactions taking place is: CH2CHCH3 + Br2 CH2BrCHBrCH3 What name is given to this type of chemical reaction? 1

2010 I2 6 26. Chemicals in food provide flavour and smell. Ketones are responsible for the flavour in blue cheese. Two examples of ketones are shown below. (a) Draw a structure for hexan-3-one. 1 (b) Suggest a name for the ketone shown below. 1 (c) Information about the boiling points of four ketones is shown in the table. Predict the boiling point of C7H14O. 1

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2014 N5 MC 9 27. The molecular formula for cyclohexane is

A C6H6 B C6H10 C C6H12 D C6H14 1

2014 N5 MC 10

28. The systematic name for the structure shown is

A 1,1-dimethylpropane B 2-methylbutane C 3-methylbutane D 2-methylpentane 1

2014 N5 MC 11

29. Petrol is a mixture of hydrocarbons. The tendency of a hydrocarbon to ignite spontaneously is measured by its octane number.

A student made the hypothesis that as the chain length of a hydrocarbon increases, the octane number decreases. Which set of three hydrocarbons should have their octane numbers compared in order to test this hypothesis? A 1, 4, 6 B 1, 2, 4 C 2, 3, 5 D 3, 4, 5 1

Hydrocarbon Octane number

1 3-methylpentane 74.5

2 butane 93.6

3 pentane 61.7

4 2-methylpentane 73.4

5 hexane 24.8

6 methylcyclopentane 91.3

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2014 N5 MC 12 30. Propene reacts with hydrogen bromide to form two products.

Which of the following alkenes does not form two products on reaction with hydrogen bromide? A But-1-ene B But-2-ene C Pent-1-ene D Pent-2-ene 1

2014 N5 9

31. Liquefied petroleum gas (LPG), which can be used as a fuel for heating, is a mixture of propane and butane.

(a) Propane and butane are members of the homologous series of alkanes.

Tick (✓) the two boxes that correctly describe members of the same homologous

series.

Tick (✓)

They have similar chemical properties.

They have the same molecular formula.

They have the same general formula.

They have the same physical properties.

They have the same formula mass.

(b) The table gives some information about propane and butane.

Alkane Boiling point (°C)

Propane -42

butane -1

Explain why butane has a higher boiling point than propane. 2

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2014 N5 10 32. The lowest temperature at which a hydrocarbon ignites is called its flash point.

(a) (i) Using the information in the table, make a general statement linking the flash point to the number of carbon atoms. 1 (ii) Predict the flash point, in °C, of decane, C10H22. 1

(b) Nonane burns to produce carbon dioxide and water.

C9H20 + 14O2 9CO2 + 10H2O Calculate the mass, in grams, of carbon dioxide produced when 32 g of nonane is burned. Show your working clearly. 3

2015 N5 MC 12

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The name of the above compound is A 2,3-dimethylpropane B 3,4-dimethylpropane C 2,3-dimethylpentane D 3,4-dimethylpentane 1

2015 N5 MC 14

34.

Which of the following is the general formula for this homologous series?

A CnH2n—4 B CnH2n+2 C CnH2n D CnH2n—2 1

Hydrocarbon Flash point (°C)

Hexane -23

Heptane -4

Octane 13

nonane 31

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2015 N5 12 35. The structural formulae of two hydrocarbons are shown.

(a) Name hydrocarbon A. 1

(b) Hydrocarbons A and B can be described as isomers. State what is meant by the term isomer. 1

(c) Hydrocarbon A can undergo an addition reaction with water to form butan-2-ol as shown.

A similar reaction can be used to produce 3-methylpentan-3-ol. Draw a structural formula for the hydrocarbon used to form this molecule. 1

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2016 N5 MC 10 36. Which of the following compounds belongs to the same homologous series as the

compound with the molecular formula C3H8? 1

2016 N5 MC 11 37. The systematic name for the structure shown is

A 1,2-dimethylpent-1-ene B 2,3-dimethylpent-1-ene C 3,4-dimethylpent-4-ene D 3,4-dimethylpent-1-ene 1

2016 N5 MC 12

38. Two isomers of butene are Which of the following structures represents a third isomer of butene?

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2016 N5 MC 14 39. The lowest temperature at which a hydrocarbon ignites is called its flash point.

Hydrocarbon Formula Boiling point (ºC) Flash point (ºC)

Hexane C6H12 63 -25

Hexane C6H14 69 -23

Cyclohexane C6H12 81 -20

Heptane C7H16 98 -1

Octane C8H18 126 15

Using information in the table, identify the correct statement. A Octane will ignite at 0 ºC. B Hydrocarbons with the same molecular mass have the same flash point. C The flash point of a hydrocarbon increases as the boiling point increases. D In a homologous series the flash point decreases as the number of carbon atoms increases. 1

2016 N5 11

40. Ethers are a group of compounds containing carbon, hydrogen and oxygen.

Name of ether Structural formula Boiling point (ºC)

Methoxyethane CH3-O-CH2CH3 7

Ethoxyethane CH3CH2-O-CH2CH3 35

X CH3-O-CH2CH2CH3 39

propoxybutane CH3CH2CH2-O-CH2CH2CH2CH3 117

(a) Name ether X. 1

(b) Suggest a general formula for this homologous series. 1

(c) Methoxyethane is a covalent molecular substance. It has a low boiling point and is a gas at room temperature. Circle the correct words to complete the sentence.

(d) Epoxides are a family of cyclic ethers. The full structural formula for the first member of this family is shown.

(i) Epoxides can be produced by reacting an alkene with oxygen. Name the alkene which would be used to produce the epoxide shown. 1

(ii) Epoxides have three atoms in a ring, one of which is oxygen. Draw a structural formula for the epoxide with the chemical formula C3H6O. 1

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Everyday Consumer Products

2006 I2 18MC 1. The method used to increase the ethanol concentration of fermentation products is A cracking B dehydration C distillation D hydrolysis 1

2008 I2 16MC 2. Fermentation of glucose to ethanol and carbon dioxide by yeast stops when the ethanol concentration reaches about 13%. This is because A the ethanol has destroyed the yeast B all the glucose has been used up C carbon dioxide is harmful to yeast D the mixture is now saturated with ethanol. 1

2009 I2 17MC 3. The above compound could be formed by adding water to 1

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2010 I2 13MC 4. Which type of reaction is shown by the following equation? A Condensation B Dehydration C Hydration D Hydrolysis 1

2011 I2 14MC 5. When propene undergoes an addition reaction with hydrogen bromide, two products are formed. Which of the following alkenes will also produce two products when it undergoes an addition reaction with hydrogen bromide? A Ethene B But-1-ene C But-2-ene D Hex-3-ene 1

2012 I2 15MC 6. Which line in the table correctly identifies Process X and Compound Y? 1

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2013 I2 13MC 7. Ethanol can be produced from sugar cane by A oxidation B fermentation C polymerisation D catalytic hydration. 1

2013 I2 14MC 8. Propan-1-ol can be dehydrated. Which of the following compounds is a product of the reaction? A Propanoic acid B Propyl propanoate C Propene D Propane 1

2011 I2 9

9.

The alcohol produced is ethanol. Draw the shortened structural formula for ethanol.

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2012 I2 7 10. Ethanol is a member of the alkanol family of compounds.

(a) Ethanol can be manufactured from ethene as shown in the following addition reaction.

What other name can be given to this type of addition reaction?

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(b) Butan-2-ol is another member of the alkanol family.

Draw the full structural formula for an isomer of butan-2-ol.

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2013 I2 13 11.

(a) Suggest a pH value for hipposudoric acid. 1

(b) Hipposudoric acid contains a hydroxyl group. Circle the hydroxyl group in the structure of hipposudoric acid.

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2009 I2 7

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12. The diagram shows how paraffin, C12H26, can be cracked. (a) Name the catalyst used in cracking. 1 (b) One of the reactions taking place when paraffin is cracked is C12H26 C8H18 + X (i) Identify molecule X. 1 (ii) Describe what would be seen when X is added to bromine solution. 1

2013 C 15

13. An antibacterial hand gel contains two alkanols, ethanol and propan-2-ol.

(a)

When alkanols are oxidised alkanoic acids are produced.

Draw the full structural formula for the alkanoic acid produced when butanol is oxidised.

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(b) Esters are produced when alkanols react with alkanoic acids. The table gives information on esters.

Suggest a name for X.

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2009 I2 10

14. The flow chart shows some of the stages in the manufacture of ethanoic acid.

(a) In the mashing process, some of the starch is broken down into glucose. Using the flow chart, write the word equation for the reaction taking place in the mashing process. 1 (b) Name process X. 1 (c) Draw the full structural formula for ethanoic acid. 1

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2010 I2 7 15. A recipe for making blackcurrant wine is shown. (a) Yeast is used to convert sugar into ethanol. (i) What name is given to this process? 1 (ii) What type of substance, found in yeast, acts as a catalyst? 1 (b) Why was the mixture cooled at step 3, before the yeast was added to it? 1 (c) When blackcurrant brandy is made from blackcurrant wine, the ethanol concentration is increased. How could this be done? 1

2014 N5 MC 13 16. Which of the following alcohols has the highest boiling point?

You may wish to use your data booklet to help you. A Propan-1-ol B Propan-2-ol C Butan-1-ol D Butan-2-ol 1

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2014 N5 8 17. Pheromones are chemicals, produced by living things, that trigger a response in members

of the same species. When a bee stings an animal the bee also releases a pheromone containing the ester below.

(a) A student made the ester above using ethanoic acid and the following alcohol.

(i) Name the functional group present in this alcohol. 1

(ii) Draw a structural formula for an isomer of this alcohol. 1

(iii) Ethanoic acid is the second member of a family of compounds which contain

the carboxyl functional group. The full structural formulae for the first three members of this family are shown. Suggest a general formula for this family of compounds. 1

(b) The table gives information on some other esters.

Alcohol Carboxylic acid Ester

Methanol Ethanoic acid Methyl ethanoate

Propanol Methanoic acid Propyl methanoate

Butanol Ethanoic acid Butyl ethanoate

Pentanol Butanoic acid Pentyl butanoate

X Y Ethyl propanoate

Name X and Y. 1

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2015 N5 MC 13 18. The shortened structural formula for an organic compound is CH3CH(CH3)CH(OH)C(CH3)3

Which of the following is another way of representing this structure? 1

2015 N5 3 19. Butter contains different triglyceride molecules.

(a) A triglyceride molecule is made when the alcohol glycerol reacts with carboxylic acids.

(Name the functional group present in glycerol. 1

(b) When butter goes off, a triglyceride molecule is broken down, producing compounds X and Y.

(i) Name compound X. 1

(ii) Describe the chemical test, including the result, to show that compound Y is unsaturated. 1

2015 N5 13

20. Succinic acid is a natural antibiotic. The structure of succinic acid is shown.

Name the functional group present in succinic acid. 1

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2016 N5 8 21. Essential oils can be extracted from plants and used in perfumes and food flavourings.

(a) Essential oils contain compounds called terpenes. A terpene is a chemical made up of a number of isoprene molecules joined together. The shortened structural formula of isoprene is CH2C(CH3)CHCH2. Draw the full structural formula for isoprene. 1

(b) Essential oils can be extracted from the zest of lemons in the laboratory by steam

distillation. The process involves heating up water in a boiling tube until it boils. The steam produced then passes over the lemon zest which is separated from the water by glass wool. As the steam passes over the lemon zest it carries the essential oils into a delivery tube. The condensed liquids (essential oils and water) are collected in a test tube placed in a cold water bath. Complete the diagram to show the apparatus required to collect the essential oils. 1

(c) Limonene, C10H16, is an essential oil which is added to some cleaning products to give

them a lemon scent.

The concentration of limonene present in a cleaning product can be determined by titrating with bromine solution.

(i) Name the type of chemical reaction taking place when limonene reacts with bromine solution. 1

(ii) Write the molecular formula for the product formed when limonene, C10H16, reacts completely with bromine solution. 1

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2016 N5 12 22. Betanin is responsible for the red colour in beetroot and can be used as a food colouring. Name the functional group circled in the diagram above. 1

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Energy from Fuels 2012 I2 5

1. The alkanals are a homologous series of compounds that all contain the elements carbon, hydrogen and oxygen.

The combustion of alkanals releases heat energy.

(a) Make a general statement linking the amount of heat energy released and the number of carbon atoms in the alkanal molecules.

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(b) Predict the amount of heat energy released, in kJ, when 1 mole of pentanal burns.

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2007 I2 15c 2. The diagram shows the chemical energies of the reactants and products when magnesium reacts with dilute acid. In what way does the energy diagram show that the reaction is exothermic? 1

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2007 H 5 3. The energy changes taking place during chemical reactions have many everyday uses. (a) Some portable cold packs make use of the temperature drop that takes place when the chemicals in the pack dissolve in water. Name the type of reaction that results in a fall in temperature. 1 (b) Flameless heaters are used by mountain climbers to heat food and drinks. The chemical reaction in a flameless heater releases 45 kJ of energy. If 200 g of water is heated using this heater, calculate the rise in temperature of the water, in °C. 1

2011 H 14 4. The enthalpies of combustion of some alcohols are shown in the table. (a) Using this data, predict the enthalpy of combustion of butan-1-ol, in kJ mol–1. 1 (b) The following apparatus was used to measure how much heat was produced when butan-2-ol, C4H9OH, was burned. Mass of butan-2-ol burned = 1·0 g Initial temperature of water = 18 °C Final temperature of water = 38 °C Use these results to calculate the heat released when 1g of butan-2-ol was burned. 1

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2012 RH 3 5. Different fuels are used for different purposes. (a) Ethanol, C2H5OH, can be used as a fuel in some camping stoves. Theoretically, the amount of heat energy that should be released when one mole (46g) of ethanol burns is 1367 kJ. Suggest two reasons why less energy is obtained from burning ethanol in the camping stove than is predicted. 2 (b) Petrol is a fuel used in cars. A car has a 50·0 litre petrol tank. Calculate the energy, in kJ, released by the complete combustion of one tank of petrol. 2

2014 N5 MC 14 6. A reaction is endothermic if

A energy is required to start the reaction B heat is released during the reaction C the temperature drops during the reaction D the temperature rises during the reaction 1

2014 N5 9

7. Liquefied petroleum gas (LPG), which can be used as a fuel for heating, is a mixture of propane and butane.

(a) 25kg of water at 10°C is heated by burning some LPG. Calculate the energy, in kJ, required to increase the temperature of the water to 30°C. You may wish to use the data booklet to help you. Show your working clearly. 3

(b) LPG is odourless. In order to detect gas leaks, ethyl mercaptan, C2H6S, a smelly gas, is added in small quantities to the LPG mixture. Suggest one disadvantage of adding sulfur compounds, such as ethyl mercaptan, to fuels such as LPG. 1

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2015 N5 8 8. A student calculated the energy absorbed by water when ethanol is burned using two

different methods.

The student recorded the following data.

Method

A B

Mass of ethanol burned (g) 0.5 0.5

Mass of water heated (g) 100 100

Initial temperature of water (°C) 24 24

Final temperature of water (°C) 32 58

(a) The final temperature of water in method B is higher than in method A.

Suggest why there is a difference in the energy absorbed by the water. 1

(b) Calculate the energy, in kJ, absorbed by the water in method B. You may wish to use the data booklet to help you. Show your working clearly. 3

2016 N5 MC 9

9. When methane burns in a plentiful supply of air, the products are

A carbon and water B carbon dioxide and water C carbon monoxide and water D carbon dioxide and hydrogen 1

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2016 N5 9 10. Ethanol can be used as an alternative fuel for cars.

(a) A student considered two methods to confirm the amount of energy released when ethanol burns. Explain which method would give a more accurate result. 2 (b) The table gives information about the amount of energy released when 1 mole of some alcohols are burned.

Name of alcohol Energy released when one mole of alcohol

is burned (kJ)

Propan-1-ol 2021

Propan-2-ol 2005

Butan-1-ol 2676

Butan-2-ol 2661

Pentan-1-ol 3329

Pentan-2-ol 3315

Hexan-1-ol 3984

(i) Write a statement linking the amount of energy released to the position of the

functional group in an alcohol molecule. 1

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(ii) Predict the amount of energy released, in kJ, when 1 mole of hexan-2-ol is burned. 1

(c) Ethanol can also be used in portable camping stoves. The chemical reaction in a camping stove releases 23 kJ of energy. If 100 g of water is heated using this stove, calculate the rise in temperature of the water, in °C. You may wish to use the data booklet to help you. Show your working clearly. 3