CIE Jun 2016 v2 Paper 3 Q1

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PMT In Questions 1 and 2 you will determine the relative atomic mass, Ar, of magnesium by two different methods. In the first method you will collect and measure the volume of gas given off in the reaction between a known mass of magnesium and a known amount of dilute sulfuric acid. The acid will be in excess. Mg(s) + H2SO4(aq)MgSO4(aq) + H2(g) FB 1 is a strip of magnesium ribbon, Mg. FB 2 is 1.00 mol dm3 sulfuric acid, H2SO4. (a) Method Read through the whole method before starting any practical work. The diagrams below may help you in setting up your apparatus. clamp water OR clamp water Fill the tub with water to a depth of about 5 cm. Fill the 250 cm3 measuring cylinder completely with water. Hold a piece of paper towel firmly over the top, invert the measuring cylinder and place it in the water in the tub. Remove the paper towel and clamp the inverted measuring cylinder so the open end is in the water just above the base of the tub. Pipette 25.0 cm3 of FB 2 into the reaction flask labelled X. Check that the bung fits tightly in the neck of flask X, clamp flask X, and place the end of the delivery tube into the inverted 250 cm3 measuring cylinder. Weigh the magnesium ribbon, FB 1, and record the mass in the space below. Remove the bung from the neck of the flask. Add the magnesium ribbon, FB 1, into the acid in the flask and replace the bung immediately. Remove the flask from the clamp and swirl it to mix the contents. Swirl the flask occasionally until no more gas is evolved. Replace the flask in the clamp. When no more gas is collected, measure and record the final volume of gas in the measuring cylinder in the space below.KEEp THE CONTENTS OF THE CONICAL FLASK X FOR USE IN QUESTION 2. ResultsUCLES 2016 9701/32/M/J/16 [2]<br /> PMT (b) Calculations Show your working and appropriate significant figures in the final answer to each step of your calculations. (i) Calculate the number of moles of gas collected in the measuring cylinder. [Assume that 1 mole of gas occupies 24.0 dm3 under these conditions.] (ii) Use your answer to (i) and the mass of magnesium, FB 1, recorded in (a) to calculate the relative atomic mass, Ar, of magnesium. moles of gas =mol Ar of magnesium =[3] [Total: 5]UCLES 2016 9701/32/M/J/16 [Turn over<br />

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