CHS Chemistry (Alkanes, Alkenes and Isomerism)

Catholic High School Sec 4 Chemistry Worksheet 21/22 - Alkanes , Alkenes & Isomerism Name : ________________ ___ ( ) Mark : Class: ____ _ Date: (A) Multiple-Choice Questions (15 marks) 1. Octane is an eight carbon alkane found in petrol. Which statement about octane is correct? A It cannot be obtained via cracking of B It has a lower boiling point than ethane. x petroleum. .,. C It reacts with bromine by substitution. D It differs from methane by a -CH2 group.X [ C. ] 2. Methane, the first member of the alkane homologous series. has a boiling point of -161 °C. Which of the following statements is true? A The second member of the alkane homologous series is C2Hs with a boiling point of -88 °C. B Some alkanes are saturated hydrocarbons . C All alkanes have the same physical properties. D All alkanes contain -G-C- bond. 3. The diagrams show the structures of three compounds . H H I I H-C~ -H I I Cl H 1 H H I I H- C - C -H I I Cl Cl 2 l l H H I I H-C -C -Cl I I H Cl 3 Which compounds can be products of substitution reactions of ethane with excess chlorine? A 1 only . C 1 and 3 only . B 2 only. D 1, 2 and 3. l 1 4. Which of the following compounds may be produced from incomplete combustion of propane? 1 Soot 2 Hydrogen 3 Carbon monoxide 4 Water A 2 and 4 only . B 1, 3 and 4 only . C 1, 2 and 4 only. D 1, 2, 3 and 4. [ ] Page 1 .. -·. . . " 11. __ :, '>n'> 1 \ ' I \ \

Cr 1ni» 1r ; 5. When 2-m:thy lbutane reacts with chlori . monoc hlon nated prod ucts f ne in the presence of UV light four different are ormed. ' H I H-C-H H I H H I I I H-C-C-C-C-H I I I I H H H H (a) Draw the full structural formula of each of the produ cts. (b) Suggest with a reason, why four different monochlorinated products might be fonned. [4] [1] I I I

6. The table shows the names and structures of some hydrocarbo ns. Cycloalkene --------- --Alkyne I Number of -­ carbon atoms 3 - -------;:-:-·--------1---------------H 4 5 'C ll'C/H c' ' H / H Cyclopropene H H ' ,, H, /c, / C, ~C-H H C I H Cvclobutene H I H- c=c-c-H I H Propyne H H H-C=e-{-{-H H H Butvne (a) In the table above, give the full structural formula and chemical name of the next member of the cycloalkane and alkyne homologous series containing 5 carbon atoms. . [4] (b) Are cycloalkenes isomers of alkynes? Explain your reasoning. {2] (c) Describe and explain the trend in boiling points as the number of carbon atoms increase in the alkynes. [2] (d) Similar to propanes, propynes also takes part in addition reactions . One such reaction is the addition of bromine across the carbon-carbon triple bond. For halogenation, the halogen atoms add to an alkyne molecule in a stepwise fashion , leading to the formation of an alkene, which can undergo further reaction to form an alkane. (i) Draw the product of the reaction when 1 (ii) mole of propyne reacts with 2 moles of aqueous bromine under an addition reaction. [11 Last updated by: CWJ 12 April 2021 Draw the product of the reaction when 1 mole of propyne reacts with 1 mole of aqueous bromine in another addition reaction . [1] Page 8

2. An alkene has the molecular formula C6H12. The following shows the full structural formula of the compound when this alkene reacts with bromine. H H H H H H I I I I I I H-C-C-C- C- C-C-H I I I I I I H H H Br Br H (a) Draw the full structural formula of two isomers of the structure above. (b) Draw the full structural formula of the starting alkene. [2] [1] (c) Explain why the reaction between the alkene and bromine is called an addition reaction . [2] 3. The table shows some data about some hydrocarbons . Hydrocarbon Empirical Molecular Melting point / Boiling point / Energy change of formula formula oc oc combustion/ kJ/mol Ethane CH3 C2Hs -183 -89 -1560 Propane C3Ha C3Ha -188 -42 -2220 Propane CH2 C3Hs -185.2 -47.6 -1911 (a) Identify which hydrocarbons belong to the same homologous series. Use the information in the table to give two pieces of evidence to show they belong to the same homologous series. [3]

(b) The enthalpy change of combustion in kJ/mol increases from ethane to propane . Suggest a reason why. 4. A student collects some data about the fat content of some margarines. The margarines tested contain a mixture of saturated fat, A, unsaturated fat. B, and water. He conducts an experiment to determine the number of drops of bromine water that will r~act with 1 O g of each type of margarine . The table shows his results. !Margarine Percentage by m~ss of Percentage by mass of Number of drops of saturated fat unsaturated fat bromine water per 10 g 1 10 -- : 80 12 2 20 ', 60 9 3 .-i; '1 60 ·j 20 3 ., (a) Describe the colo1,1rm81lge~d when bromine reacts with margarine 1. [1) (b) Describe how margarine 2 can b~ converted to margarine 3 , stating clearly, the name of the reaction, reagents and the conditions requir ed. [2] (c) A fourth type of margarine, contains 30% by mass of saturated fat and 30% by mass of water. Estimate the number of drop s of brorrune water that reacts with 10 g of this margarine . [1) (d) Pure fat has a molecular mass of 600 . 100 g of pure fat reacts with 254 g of iodine . How many double bonds are there in each. molecule of the fat? Show your working clearly . [3]

Ln- , tr , k. the hyd rocarbon octadecane 15. Which of the followi ng would not be a likely product on crac ing ' C 1sH3s? 5 C H 1 H2 2 C9H1a 3 C9H2o 4 C9H22 18 36 A 4 only . C 1 , 2 and 4 only. B 1 and 5 only. D 1 , 3 and 5 only . (B} Structured Questions [35 marks) 1. Two possible fuels for use in car engines are octane and butane. The table gives some data about these two fuels. Fuel Molecular Melting point / °C Boiling point / °C Energy change of formula combustion/ kJ/mol Octane CaH,a -57 125 -5460 Butane C4H10 -140 -1 -2874 (a} The table gives value for the energy change of combustion for each fuel in kJ/mol. Calculate the energy output for 1 g of each fuel. (b) Use the values you have calculated and information in the table to discuss the advantages and disadvantages of using each fuel in cars . [2] [2]

10. When 1 mole of hydrocarbon X burns completely in excess oxygen, it produces 18 g of water and 88 g of carbon dioxide. What is the formula of the hydrocarbon X? 11. Which of these statements comparing alkanes and alkenes is true? A Alkanes are more reactive than alkenes. B Alkenes decolourise bromine water rapidly under room temperature conditions but alkanes do not. C Alkenes undergo substitution reactions, but alkanes undergo addition reactions. D Alkanes are flammable, but alkenes are not. 12. Which of the following structural formulae is not an isomer of the others? A H H 8 H I I I H-C- C - H HH-cl-HH H I I I I I H- C-C- H H-c-c-c-c-H I I I I I I H H H H H H C H H H H I I I I H-C-C-C=C I I I H H H D H H H H I I I I H-C-C=C-C-H ~ ~ 1. [ ] 13. Which of these statements about structural isomers are correct? 1 Isomers are compounds with different structural formula . 2 Isomers are compounds with different molecular formula . 3 Isomers have the same relative molecular mass. 4 Isomers have similar chemical properties. 5 Isomers belong to the same homologous series. A 1 and 3 only. B 2 and 3 only. C 3, 4 and 5 only. D 1, 3, 4 and 5 only. ( l 14. Which properties will be the same for both molecules shown below? H H H H I I I I H-C-C - 0-H H-C-0-C-H I I I I H H H H 1 Empirical formula 2 Functional group 3 Molecular formula 4 Structural formula 5 Boiling point A 1, 2, 3 and 4 only B 1 and 3 only . C 1, 3 and 5 only D 2 and 3 only [ ] n--- '1

- ll ,,?1-.ath::5. Al"t::tH.:S i:; l•;eJtll • :1 c. m C , ·:11-:,tf\. 5. Which of these molecules are structural isome rs of eac h othe r? (Th I CT·h CIICH: Cl l3 A 1 and 2 only. C 2 and 4 only. CHJ ClhC H~CH I CH, 3 B 1 and 3 only. D 3 and 4 only. 6. How many other isomers does the mo