Farr High School. NATIONAL 5 CHEMISTRY Unit 2 Nature s Chemistry. Exam Questions (UPDATED MAY 2017)

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1 Farr High School NATIONAL 5 CHEMISTRY Unit 2 Nature s Chemistry Exam Questions (UPDATED MAY 2017) 1

2 Homologous series I2 13MC The above structural formulae represent A the same hydrocarbon B Different hydrocarbons C Isomers D Isotopes 1 2. The first three members of the alkanone series are: 2006 I2 14MC What is the general formula for this homologous series? A C n H 2n-2 O B C n H 2n O C C n H 2n-1 O D C n H 2n+2 O 1 3. The structural formula for hydrocarbon X is 2006 I2 16MC 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 C n H 2n I2 13MC 4. Which of the following compounds fits the general formula, C n H 2n, and will rapidly decolourise bromine solution? A Cyclopentane B Cyclopentene C Pentane D Pentene 2

3 I2 12MC The name of the above compound is A 1, 1 dimethylpropane B 2-ethylpropane C 2-methylbutane D 3-methylbutane I2 10 MC Which of the following compounds is an isomer of the one above? 1 7. Three members of the cycloalkane homologous series are: 2008 I2 14MC The general formula for this homologous series is A C n H 2n+2 B C n H 2n C C n H 2n 2 D C n H 2n

4 8. Which of the following molecules is an isomer of heptane? 2008 I2 15MC 2009 I2 15MC 9. Which of the following could be the molecular formula of a cycloalkane? A C 7 H 10 B C 7 H 12 C C 7 H 14 D C 7 H I2 10MC 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 C 2 H 4 B C 2 H 6 C C 4 H 8 D C 4 H I2 16MC 11. The shortened structural formula for an organic compound is CH 3 CH(CH 3 )CH(OH)C(CH 3 ) 3. Which of the following is another way of representing this structure? 1 4

5 2009 I2 12MC 12. Which of the following hydrocarbons does not belong to the same homologous series as the others? A CH 4 B C 3 H 8 C C 4 H 10 D C 6 H The structural formulae for some hydrocarbons are shown below CRED 4 (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 I 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 5

6 2013 I Crude oil is a mixture of hydrocarbons which can be separated into fractions by fractional distillation. Petrol contains the following molecule. Name this molecule Heptane can be cracked as shown C 16 One of the reactions which takes place is: The product C 3 H 6 decolourises bromine solution quickly. Draw a structural formula for an isomer of C 3 H 6, which would not decolourise bromine solution quickly The monomer in superglue has the following structure C 20 Bromine reacts with the monomer to produce a saturated compound. Draw the structural formula for this compound. 1 6

7 18.(a) Ethylthioethane belongs to a homologous series of compounds called thioethers C 22 What is meant by a homologous series? 1 (b) Ethylthioethane is formed when ethylthiol reacts with bromoethane as shown. Draw the full structural formula for the thioether produced in the following reaction. 1 (c) Ethylthioethane can also be formed by the reaction of ethylthiol with ethene. 1 Suggest a name for the type of chemical reaction taking place. 7

8 2007 I 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 I 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 8

9 2008 I 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 CCl 2 F 2 and compounds used to replace it. (i) Draw a possible structure for Replacement 2. 1 (ii) Compared with CCl 2 F 2, 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 9

10 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 I2 7 (a) What does the term synthetic mean? 1 (b) Copy out the triglyceride and circle an ester link. 1 (c) Name X I 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 10

11 2009 I 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 11

12 25. The diagram below shows the apparatus used to crack a hydrocarbon I2 5 (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: CH 2 CHCH 3 + Br 2 CH 2 BrCHBrCH 3 What name is given to this type of chemical reaction? I 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 C 7 H 14 O. 1 12

13 27. The molecular formula for cyclohexane is 2014 N5 MC 9 A C 6 H 6 B C 6 H 10 C C 6 H 12 D C 6 H N5 MC 10 The systematic name for the structure shown is A 1,1-dimethylpropane B 2-methylbutane C 3-methylbutane D 2-methylpentane N5 MC Petrol is a mixture of hydrocarbons. The tendency of a hydrocarbon to ignite spontaneously is measured by its octane number. Hydrocarbon Octane number 1 3-methylpentane butane pentane methylpentane hexane methylcyclopentane 91.3 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,

14 30. Propene reacts with hydrogen bromide to form two products N5 MC 12 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 N 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. They have similar chemical properties. They have the same molecular formula. They have the same general formula. Tick ( ) They have the same physical properties. They have the same formula mass. 1 (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 14

15 2014 N The lowest temperature at which a hydrocarbon ignites is called its flash point. Hydrocarbon (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, C 10 H (b) Nonane burns to produce carbon dioxide and water. C 9 H O 2 9CO H 2 O Flash point ( C) Hexane -23 Heptane -4 Octane 13 nonane 31 Calculate the mass, in grams, of carbon dioxide produced when 32 g of nonane is burned. Show your working clearly N5 MC 12 The name of the above compound is A 2,3-dimethylpropane B 3,4-dimethylpropane C 2,3-dimethylpentane D 3,4-dimethylpentane N5 MC 14 Which of the following is the general formula for this homologous series? A C n H 2n 4 B C n H 2n+2 C C n H 2n D C n H 2n

16 35. The structural formulae of two hydrocarbons are shown N5 12 (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 16

17 2016 N5 MC Which of the following compounds belongs to the same homologous series as the compound with the molecular formula C 3 H 8? N5 MC 11 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 Two isomers of butene are 2016 N5 MC 12 Which of the following structures represents a third isomer of butene? 1 17

18 2016 N5 MC The lowest temperature at which a hydrocarbon ignites is called its flash point. Hydrocarbon Formula Boiling point (ºC) Flash point (ºC) Hexane C 6 H Hexane C 6 H Cyclohexane C 6 H Heptane C 7 H Octane C 8 H 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 Ethers are a group of compounds containing carbon, hydrogen and oxygen. Name of ether Structural formula Boiling point (ºC) 2016 N5 11 Methoxyethane CH 3 -O-CH 2 CH 3 7 Ethoxyethane CH 3 CH 2 -O-CH 2 CH 3 35 X CH 3 -O-CH 2 CH 2 CH 3 39 propoxybutane CH 3 CH 2 CH 2 -O-CH 2 CH 2 CH 2 CH (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) (ii) Epoxides can be produced by reacting an alkene with oxygen. Name the alkene which would be used to produce the epoxide shown. 1 Epoxides have three atoms in a ring, one of which is oxygen. Draw a structural formula for the epoxide with the chemical formula C 3 H 6 O. 1 18

19 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 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 I2 17MC The above compound could be formed by adding water to 1 19

20 4. Which type of reaction is shown by the following equation? 2010 I2 13MC A Condensation B Dehydration C Hydration D Hydrolysis 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 I2 15MC Which line in the table correctly identifies Process X and Compound Y? 1 20

21 2013 I2 13MC 7. Ethanol can be produced from sugar cane by A oxidation B fermentation C polymerisation D catalytic hydration Propan-1-ol can be dehydrated I2 14MC Which of the following compounds is a product of the reaction? A Propanoic acid B Propyl propanoate C Propene D Propane I The alcohol produced is ethanol. Draw the shortened structural formula for ethanol. 1 21

22 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 I2 7 What other name can be given to this type of addition reaction? 1 (b) Butan-2-ol is another member of the alkanol family. Draw the full structural formula for an isomer of butan-2-ol I2 13 (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 I2 7

23 12. The diagram shows how paraffin, C 12 H 26, can be cracked. (a) Name the catalyst used in cracking. 1 (b) One of the reactions taking place when paraffin is cracked is C 12 H 26 C 8 H 18 + X (i) Identify molecule X. 1 (ii) Describe what would be seen when X is added to bromine solution An antibacterial hand gel contains two alkanols, ethanol and propan-2-ol C 15 (a) When alkanols are oxidised alkanoic acids are produced. Draw the full structural formula for the alkanoic acid produced when butanol is oxidised. 1 23

24 (b) Esters are produced when alkanols react with alkanoic acids. The table gives information on esters. Suggest a name for X The flow chart shows some of the stages in the manufacture of ethanoic acid I2 10 (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 24

25 15. A recipe for making blackcurrant wine is shown I2 7 (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? Which of the following alcohols has the highest boiling point? You may wish to use your data booklet to help you N5 MC 13 A Propan-1-ol B Propan-2-ol C Butan-1-ol D Butan-2-ol 1 25

26 2014 N 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 26

27 2015 N5 MC The shortened structural formula for an organic compound is CH 3 CH(CH 3 )CH(OH)C(CH 3 ) 3 Which of the following is another way of representing this structure? 2015 N 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 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 Succinic acid is a natural antibiotic. The structure of succinic acid is shown N5 13 Name the functional group present in succinic acid. 1 27

28 2016 N 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 CH 2 C(CH 3 )CHCH 2. 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, C 10 H 16, 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, C 10 H 16, reacts completely with bromine solution. 1 28

29 2016 N 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 29

30 Energy from Fuels 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 I2 5 (a) Make a general statement linking the amount of heat energy released and the number of carbon atoms in the alkanal molecules. 1 (b) Predict the amount of heat energy released, in kj, when 1 mole of pentanal burns 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 30

31 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 The enthalpies of combustion of some alcohols are shown in the table H 14 (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 31

32 5. Different fuels are used for different purposes. (a) Ethanol, C 2 H 5 OH, can be used as a fuel in some camping stoves RH 3 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 A reaction is endothermic if 2014 N5 MC 14 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 N 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, C 2 H 6 S, 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 32

33 2015 N 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) Mass of water heated (g) Initial temperature of water ( C) Final temperature of water ( C) (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 When methane burns in a plentiful supply of air, the products are 2016 N5 MC 9 A carbon and water B carbon dioxide and water C carbon monoxide and water D carbon dioxide and hydrogen 1 33

34 2016 N 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 34

35 (ii) (c) Predict the amount of energy released, in kj, when 1 mole of hexan-2-ol is burned. 1 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 35