Edexcel Jan 2016 (IAL) Paper 3 Q5

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A E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D 5 A method for the preparation of iodoethane is given in outline below. Procedure Step 1 Suitable quantities of red phosphorus and iodine are placed in a round-bottom flask. The flask is fitted with a reflux condenser and immersed in cold water. Step 2 Step 3 Step 4 Step 5 Step 6 Step 7 Step 8 Using a dropping pipette, a suitable volume of ethanol is added, in 1 cm3 portions, down the condenser. After the addition of the ethanol is complete, and a further 15 minutes have passed, the cold water bath is removed and the mixture in the flask is heated under reflux for 45 minutes. The apparatus is allowed to cool and the condenser is rearranged for distillation. The crude iodoethane is distilled off. The distillate is washed with dilute sodium carbonate solution. The washed iodoethane is separated from the aqueous solution. Anhydrous calcium chloride is added to the washed iodoethane. The equations for the reactions are 2P + 3I2 (cid:111) 2PI 3 3CH3CH2OH + PI3 (cid:111) 3CH 3CH2I + H3PO3 (a) What does the way in which ethanol is added in step 2 suggest about the nature of the reaction? (1)A E R A S I H T N I E T I R W T O N O D *P46939A01520* 15 Turn over<br /> (b) A student drew a diagram of the apparatus used in step 5. There are a number of errors in the diagram. D O N O T W R I T E I N T H I S A R E A (i) One of the errors is that the flow of water in the condenser is the wrong way round. Explain the effect of this error. (1)(ii) Identify the most significant error in the diagram and explain the effect of this. (1) ErrorEffect16 *P46939A01620* D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A<br /> A E R A S I H T N I E T I R W T O N O D (c) Suggest why, in step 6, the crude iodoethane is washed with dilute sodium carbonate solution. (1)(d) Draw a diagram of the apparatus that would be used in step 7 to separate the iodoethane. Name the apparatus and label its contents. The density of iodoethane is 1.5 g cm3 and the density of the aqueous solution is about 1.0 g cm3. (3) Name of apparatusDiagram A E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D (e) How will the appearance of the iodoethane be changed by the addition of anhydrous calcium chloride in step 8? (1)(f) How would the iodoethane be separated from the calcium chloride after step 8? (1)*P46939A01720* 17 Turn over<br /> (g) To obtain pure iodoethane, one further step in the preparation is needed. What is this step? (1)(h) It is not possible to effectively produce iodoethane by reacting ethanol with a mixture of sodium iodide and 50% sulfuric acid. This is because the sulfur in the sulfuric acid can be reduced to form substances such as hydrogen sulfide and sulfur. State what happens to the iodide ions in the sodium iodide when this occurs. (1)(Total for Question 5 = 11 marks) TOTAL FOR PAPER = 50 MARKS 18 *P46939A01820* D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A<br />

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