Edexcel Jan 2010 Paper 3 Q4

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PMT 4 An experiment to prepare a sample of 2-chloro-2-methylpropane uses the reaction of 2-methylpropan-2-ol with concentrated hydrochloric acid. (CH3)3COH + HCl(CH3)3CCl + H2O The steps of the experimental procedure are as follows 1. Place 0.20 mol of 2-methylpropan-2-ol and 70 cm3 of concentrated hydrochloric acid in a large conical flask. 2. Stopper and shake the flask at intervals, releasing any pressure after each shaking. 3. Separate the 2-chloro-2-methylpropane from the aqueous solution using a separating funnel. 4. To the 2-chloro-2-methylpropane in the separating funnel, add 20 cm3 of sodium hydrogencarbonate solution. Shake the separating funnel, carefully releasing carbon dioxide frequently. 5. Separate the 2-chloro-2-methylpropane and repeat the washing with sodium hydrogencarbonate solution until this washing step is no longer necessary. 6. Transfer the 2-chloro-2-methylpropane to a small conical flask and add a suitable drying agent. 7. Filter off the drying agent, collecting the 2-chloro-2-methylpropane into a distillation flask. Heat the flask, collecting the fraction that distils off between 50 C and 52 C. Data Property Density / g cm3 Molar mass / g mol1 Boiling temperature / C 2-methylpropan-2-ol 2-chloro-2-methylpropane 0.789 74.1 82.4 0.842 92.6 50.8 10 *N34104A01016*<br /> PMT (a) Calculate the volume of 2-methylpropan-2-ol used in the preparation. (b) Draw a diagram of a separating funnel that could be used in step 3. Label the 2-chloro-2-methylpropane layer. (c) (i) Suggest why the product is washed with sodium hydrogencarbonate solution (step 4). (1) (2) (1)(ii) How would you know that no further washing with sodium hydrogencarbonate was necessary? (1)*N34104A01116* 11 Turn over<br /> PMT (d) Suggest a suitable drying agent to dry the 2-chloro-2-methylpropane (step 6). (1)(e) Draw a labelled diagram of the apparatus you would use to carry out the final distillation (step 7). (4) 12 *N34104A01216*<br /> PMT (f) A reaction produced 18.7 cm3 of 2-chloro-2-methylpropane starting from 0.20 mol 2-methylpropan-2-ol. Calculate the percentage yield of the product of this reaction. (g) A suitable chemical test for the chlorine in a chloroalkane, such as 2-chloro-2-methylpropane, is to add the chloroalkane to a mixture of aqueous silver nitrate solution and ethanol. (i) Suggest why ethanol is added to the mixture. (2) (1)(ii) Give the expected result of this test. (1)(Total for Question 4 = 14 marks) TOTAL FOR PAPER = 50 MARKS *N34104A01316* 13<br />

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