Beatty 19.3_Alkenes WS1_2023_Answers1

1 Beatty Secondary School Science Department (Chemistry Unit) Chemistry 6092 Name: ___________________________________ ( ) Date: _______________ Class: 4E1 TOPIC: ALKENES (WORKSHEET 1) Learning Objectives: (a) Describe the alkenes as an homologous series of unsaturated hydrocarbons with the general formula CnH2n. (b) Draw the structures of unbranched alkenes, C2 to C 4, and name the unbranched alkenes, ethene to butene. (c) Describe the manufacture of alkenes and hydrogen by cracking hydrocarbons and recognise that cracking is essential to match the demand for fractions containing smaller molecules from the refinery process. (d) Describe the difference between saturated and unsaturated hydrocarbons from their molecular structures and by using aqueous bromine. (e) Describe the properties of alkenes (exemplified by ethene) in terms of combustion, polymerisation and the addition reactions with bromine, steam and hydrogen. (f) State the meaning of polyunsaturated when applied to food products. (g) Describe the manufacture of margarine by the addition of hydrogen to unsaturated vegetable oils to form a solid product. Multiple-Choice Questions 1 What feature would show that a compound must be an alkene? A if it only contains carbon and hydrogen B if it reacts only with bromine C if it is a hydrocarbon with a C═C bond D if it burns in air with a smoky flame ( C ) 2 Which of the followin g would be a likely prod uct on cracking the hydrocarbon octadecane, C18H38? A C9H18 B C9H22 C C18H40 D C36H74 ( A ) 3 The cracking o f one mole of X produces two moles of ethene , two moles of prope ne and one mole of propane. How many carbon atoms does one molecule of X contain? A 8 B 10 C 13 D 16 ( C )

2 4 Which statements about the cracking of hydrocarbons are correct? 1 Cracking involves breaking down hydrocarbon molecules. 2 One of the products of cracking is always unsaturated. 3 Cracking is essential because of the demand for fractions containing smaller molecules. A 1 and 2 only B 2 and 3 only C 1 and 3 only D 1, 2 and 3 ( D ) 5 Which structural formula represents an unsaturated hydrocarbon? ( A ) 6 Compounds X and Y are two different alkenes. Which statement about X and Y is not correct? A They both undergo addition reactions. B They have the same empirical formula. C They both contain carbon and hydrogen only. D They have the same boiling point. ( D ) 7 Which one of these equations does not show an addition reaction? A CH3Cl + Cl2 → CH2Cl2 + HCl B C3H6 + Br2 → C3H6Br2 C C4H8 + H2 → C4H10 D nC2H4 → [ CH2-CH2 ]n ( A ) 8 Compound Y has the e mpirical formula CH 2, has an M r of 56 and forms two alco hols that have different structural f