Edexcel Jan 2015 (IAL) Paper 3 Q2

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2 A white powder is the carbonate of an element in Group 2. Its formula can be written XCO3. 0.150 g of the pure carbonate was mixed with excess dilute hydrochloric acid. The following reaction occurred. XCO3(s) + 2HCl(aq) (cid:111) XCl2(aq) + CO2(g) + H2O(l) (a) Describe the test for carbon dioxide. (1) TestObservation(b) The carbonate and dilute hydrochloric acid were mixed in a conical flask with a side arm. Complete the diagram below to show how to collect the carbon dioxide and measure its volume. (2) carbonate acid (c) The volume of carbon dioxide, measured at room temperature and pressure, was 41 cm3. Calculate the number of moles of gas formed. [The molar volume of a gas under these conditions is 24 dm3 mol1.] (1) *P45043A0616*<br /> (d) Use your answer to (c), and the mass of the carbonate used, to calculate the molar mass of XCO3. (e) Deduce the value which this experiment gives for the relative atomic mass of X. Suggest which Group 2 metal is most likely to be X. (f) Suggest why less gas is collected than expected. You should assume that the reaction is complete and no gas escapes. (2) (1) (1)(g) What would be observed when a flame test is carried out on XCO3? (1)(h) A student attempted to determine the molar mass of other carbonates of Group 2 by the method used in this question. The student measured the volume of gas produced by each carbonate, but replaced hydrochloric acid with sulfuric acid. Explain why the results of the students experiments would give very inaccurate values for the molar mass of some carbonates of Group 2. (2)(Total for Question 2 = 11 marks) *P45043A0716* Turn over<br />

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