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 Las