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

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1 Farr igh School NATIONAL 5 EMISTRY Unit 2 Nature s hemistry Question Booklet (UPDATED MAY 2017) 1

2 omologous Series 1. What is meant by a homologous series? 2. What is the general formula for the alkanes? 3. opy and complete the table for the first 8 alkanes. Name Molecular Formula Full Structural Formula Shortened Structural Formula methane propane hexane 5 12 octane Why are alkanes described as saturated hydrocarbons? 5. The following table gives the boiling points of the first six alkanes: Alkane Boiling point ( o ) Methane -164 Ethane -89 Propane -42 Butane -1 Pentane 36 exane 69 a) Use the information in the table to draw a spike graph of boiling points against the number of carbon atoms in the molecules. b) Describe the trend in boiling points. c) Estimate the boiling points of i) heptane ii) octane 2

3 6. rude oil contains a mixture of different alkanes. The alkanes can be separated into useful products by the process shown below: a) What is the name of this process? b) Which of the following physical properties is made use of when separating the fractions in crude oil? A melting point B viscosity boiling point D solubility c) State what is meant by the terms: (i) Flammability (ii) Viscosity d) Which of the following statements is true for petrol. A It has a chain length of 1 4 and is a low boiling point liquid. B It has a chain length of 5 12 and is a low boiling point liquid. It has a chain length of 5 12 and is a high boiling point liquid. D It has a chain length of 9 16 and is a low boiling point liquid. e) Place the fractions diesel, fuel gas, bitumen and petrol in order of: (i) ease of evaporation easiest first (ii) flammability most flammable first (iii) viscosity most viscous first f) Explain why petrol has a lower boiling point than lubricating oil. g) Explain why lubricating oil is less flammable than naphtha. h) Explain why diesel is more viscous than naphtha. i) What two products are always made when hydrocarbons combust in a plentiful supply of oxygen? 3

4 7. What is the general formula for the alkenes? 8. opy and complete the table for the first 7 alkenes. Name Molecular Formula Full Structural Formula Shortened Structural Formula ethene butene 2 = heptene octene 2 = Why are alkenes called unsaturated hydrocarbons? 10. Describe the test and the result for an unsaturated hydrocarbon. 11. omplete the diagrams showing the addition reactions. Write word equations for the reactions. 12. Explain how hydrogenation is used to produce margarine from olive oil. 4

5 13. What is the general formula for the cycloalkanes? 14. opy and complete the table for the first 6 alkanes. Name Molecular Formula Structural Formula cyclopropane cyclohexane cycloheptane Propene and cyclopropane both have the formula 3 6. Describe a test that could be carried out to determine which chemical is which. 16. What word is used to describe chemicals with the same molecular formula but different structural formula? 17. Write the molecular formula and give the systematic names for the following chemicals: 5

6 18. Draw the structural formula for the following hydrocarbons: a) pent-2-ene b) 2-methylpentane c) 2,3-dichlorohexane d) 2,3-dimethylpent-1-ene 19. The names of some hydrocarbons are shown. A cyclobutane B cyclopentane butane D propane E ethane F butene a) Identify the two isomers. b) Identify the hydrocarbon that reacts quickly with bromine solution. c) Identify the hydrocarbon which is a liquid at 25 o. You may wish to use the data booklet to help you. 20. The grid shows the formulae for a number of hydrocarbons. A B D 3 E 2 2 F = 2 2 = a) Identify the two isomers of 2 =- 2-3 b) Identify cyclopropane. c) Which box would be the product of box E reacting with hydrogen. 21. Identify the homologous series each of the following molecules belongs to and name the compound shown. a) O b) c) O d) 3 2 OO e) 3 3 f) O 6 O

7 22. The dienes are a homologous series of hydrocarbons which possess two carbon to carbon double covalent bonds per molecule of diene. The first three members of the diene series have the following molecular formulae: a) Are dienes, saturated or unsaturated molecules. Explain your answer. b) What would be the molecular formula of the diene with 7 carbon atoms? c) What is general formula for the dienes? d) Draw a possible structural formula for the diene with formula The following reaction shows what happens to an alkene when it reacts with ozone. ozone + ozone O + O a) Draw the structural formulae of the products you would expect from the following reaction. + ozone b) Reaction with ozone and another alkene produces only one product. Draw the structural formula of the alkene which would react in this way. 24. Draw full structural formula for two isomers that have the molecular formula 4 8 and belong to two different homologous series. Give systematic names for the two isomers. 7

8 Everyday onsumer Products 1. Describe what happens during fermentation. Include the word equation and the chemical equation as part of your answer. 2. Describe how changing the temperature affects the efficiency of an enzyme. 3. What process is used to increase the concentration of alcohol? 4. Explain why alcohol and water can be separated in this way. 5. What is the general formula for alcohols? 6. Name and draw the functional group for alcohols. 7. Describe how ethanol can be made from ethene. 8. Give the names of the following alcohols : 9. Draw the full structural formulae of the following alcohols and give their names. a) 3 2 O b) 3 (O) 3 c) O d) 3 (O) Draw the shortened structural formulae for : a) butan-1-ol b) hexan-3-ol c) octan-2-ol 11. Two isomeric straight chain alcohols, each having 4 carbon atoms, are known. Draw a structural formula for each of these alcohols and write the name. 12. Besides alcoholic beverages, give two uses of alcohols. 8

9 13. Give the general formula for carboxylic acids. 14. Name and draw the functional group for carboxylic acids. 15. Draw the full structural formula for the following: a) ethanoic acid b) pentanoic acid c) heptanoic acid 16. Give 3 uses for carboxylic acids. 17. arboxylic acids are weak acids. What does this mean? 18. The table below shows the boiling points for some carboxylic acids. Acid Formula mass Boiling point o Methanoic acid Ethanoic acid Propanoic acid Butanoic acid a) Present this information as a bar graph. b) Predict the boiling point of pentanoic acid. 19. From the list of chemicals below, identify a) the alcohols b) the carboxylic acids 9

10 Energy From Fuels 1. Write balanced equations for the combustion of: a) methane b) propane c) methanol 2. The formula for measuring enthalpy change is E h = c x m x T Write down what each of the symbols in the equation stands for and the units that they are measured in. 3. omplete the sentences below using the following words: endothermic exothermic lost reactants negative joules surroundings The symbol for enthalpy change is E h and the units are. In an exothermic reaction energy is to the surroundings. When the products have more energy than the, the reaction is. It will take in energy from its. ombustion reactions are so E h is. 4. alculate the heat required to raise the temperature of: a) 1 kg of water by 15 o. b) 8 kg of water by 37 o. c) 250 cm 3 of water by 20 o. d) 500 cm 3 of water by 55 o. e) 100 cm 3 of water by 13 o. 5. When some ethane was burned, it heated 200 g of water from 15.5 o to 37.0 o. a) Write a balanced symbol equation for the reaction. b) alculate E h. 6. In an experiment burning propanol a pupil heated 100g of water using a spirit burner. The resulting change in temperature was from 10.5 o to 42.5 o. a) Write a balanced symbol equation for the reaction. b) alculate E h. 10

11 O 2 2O O What mass of water vapour is produced on burning 7g of ethene? O 2 2 O What mass of water vapour is produced on burning 1g of hydrogen? 9. 2O + O 2 2O 2 What mass of carbon monoxide must be burned to give 4.4g of carbon dioxide? 10. What mass of carbon dioxide is produced on burning 8 g of methane ( 4 ) completely in oxygen? 11. What mass of carbon dioxide is produced on burning 2.3 g of ethanol ( 2 5 O) completely in oxygen? 11