Edexcel Jun 2016 (IAL) Paper 2 Q

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15 Hydrated barium nitrate, Ba(NO3)2.4H2O, is strongly heated in a boiling tube and the following changes occur. Stage 1 The white solid forms a clear colourless solution. Stage 2 Stage 3 Condensation forms around the mouth of the boiling tube and a white solid starts to form at the bottom of the tube. As the heating continues, the colourless solution disappears leaving another white solid. Stage 4 This white solid melts. Stage 5 Nitrogen dioxide and oxygen gases are given off, and barium oxide is left in the test tube. (a) (i) Give the formula for the white solid formed in Stage 3. (1)(ii) What would you see when nitrogen dioxide is given off in Stage 5? (1)(iii) Describe the test for oxygen and its positive result. (1)(iv) Write the equation for the complete thermal decomposition of hydrated barium nitrate, Ba(NO3)2.4H2O. State symbols are not required. (2) 16 *P46659A01624*<br /> (b) Describe a simple test tube experiment that you can use to compare the thermal stabilities of anhydrous barium nitrate and anhydrous calcium nitrate. State two essential conditions necessary to ensure a fair test. You may wish to draw a diagram. Detailed measurements are not required. (3)*(c) Explain why anhydrous calcium nitrate decomposes more readily than anhydrous barium nitrate. (3)(d) The chlorides of calcium and barium can be distinguished using flame tests. State what you would see in each test. (2) Calcium chloride Barium chloride(Total for Question 15 = 13 marks) TOTAL FOR SECTION B = 41 MARKS *P46659A01724* 17 Turn over<br /> SECTION C Answer ALL the questions. Write your answers in the spaces provided. 16 Sunflower oil is an important edible oil. It can be used as an alternative to butter in cooking. A useful method of comparing fats and oils is by measuring their iodine values. An iodine value is the amount of iodine in grams that reacts with 100 g of a fat or oil. The iodine value is a measure of the degree of unsaturation of the fat or oil. The iodine value of sunflower oil can be determined in the following way. Add 0.200 g of sunflower oil to a 250 cm3 conical flask. Add 10 cm3 of solvent to dissolve the oil. Add 10.0 cm3 of a solution of iodine monochloride, called Wijs solution. Stopper the flask and allow to stand in the dark for half an hour. Add 15 cm3 (an excess) of 10% potassium iodide solution and 100 cm3 of water, and shake the mixture. Titrate the liberated iodine with 0.100 mol dm3 sodium thiosulfate solution. This gives the sample titre. Carry out a blank titration with the same sodium thiosulfate solution, using 10 cm3 of solvent, 10.0 cm3 of Wijs solution, 15 cm3 of 10% potassium iodide solution and 100 cm3 of water. (a) Trichloromethane and 1,1,1-trichloroethane are two possible solvents for this reaction. (i) Give the skeletal formulae for trichloromethane and 1,1,1-trichloroethane . (2) Trichloromethane 1,1,1-trichloroethane 18 *P46659A01824*<br />

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