Set 20 Chemistry [Paper] 2

1 SECTION A (60 Marks) Answer only three questions from this section . 1. 6.0g of bromoalkane, P C nH2n + 1 Br contains 65.04% by mass of bromine . a) Determine the molecular formula of bromoalkane , P. (03 marks) b) Write the structural formulae and IUPAC names of all the possible isomers of bromoalkane, P. (02 mark s) c) When bromoalkane, P is refluxed with aqueous potassium hydroxide solution, Compound, Q is formed. Compound, Q formed two layers after five minutes when treated with a mixture of concentrated hydrochloric acid and anhydrous zinc chloride. Identify bromoalkane, P and compound, Q. (02 marks) d) Write equations and suggest mechanism for the reaction of bromoalkane , P and: i) Alkaline solution of phenol. (03 marks) ii) Hot solution of potassium hydroxide in ethanol. (03 marks) e) Using equations show how bromoalkane, P can be converted to 2 - methylpropan -2-ol. (04 marks) f) Name the reagent that can be used to distinguish between bromoalkane, P and compound, Q, State what would be observed when the reagent is treated with each compound. (03 marks) 2. a) What is meant by the following terms? (@01 mark) i) Freezing point. ii) Freezing point depression. b) (i) Describe an experiment that can be carried out to determine the relative molecular mass of a substance by fre ezing point method.(Diagram NOT required) (06 marks) (ii)Explain why freezing point method is not suitable for determination of relative molecular mass of benzoic acid in benzene. (03 marks) c) The table below shows the freezing points of various solutions of cane sugar in solvent, X. Mass of cane sugar in 1,000g of X 26 42 66 78 118 148 173 Freezing point ( ᵒC) 5.11 4.87 4.51 4.33 3.73 3.28 2.90 i) Plot a graph of freezing point …