16 (2410U20-1) Examiner only 12. (a) Y is a halogenocompound in which each molecule contains one atom of chlorine, bromine or iodine. (i) Describe a chemical test to determine which halogen is present in Y. [3] (ii) Y contains four carbon atoms in each molecule. The percentage by mass of halogen present in Y is less than 40%. Identify Y. Explain how you reached your conclusion. [2] © WJEC CBAC Ltd. 16 (2410U20-1) Turn over. 17 Examiner only (b) (i) Halogenoalkanes react with aqueous sodium hydroxide. Draw the mechanism to show the reaction of 1-chloropropane with aqueous sodium hydroxide. You should include all charges, partial charges and lone pairs, and curly arrows to show electron movement. [4] (ii) Name the type of reaction shown in part (i). [1] ................................................................................................................ (c) Halogenoalkanes can also take part in an elimination reaction. 2-Chloropentane undergoes elimination in a similar way to 1-chloropropane. (i) Give the reagent and conditions needed for 2-chloropentane to undergo elimination. [1] (ii) When 2-chloropentane undergoes elimination, two structural isomers are formed. Give the structures of these two isomers. [2] © WJEC CBAC Ltd. 17 13