Edexcel Jan 2014 (IAL) Paper 1 Q18

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18 Barium chloride can be made by reacting solid barium carbonate with dilute hydrochloric acid in the following reaction. BaCO3(s) + 2HCl(aq) (cid:111) BaCl2(aq) + CO2(g) + H2O(l) (a) (i) Write the ionic equation for the reaction of solid barium carbonate with hydrogen ions from the hydrochloric acid. State symbols are not required. (ii) State two observations you would make while the reaction is taking place. No change of colour occurs. (1) (2) Observation 1Observation 2(b) In an experiment to prepare crystals of hydrated barium chloride, BaCl2.2H2O, a volume of 25.0 cm3 of 2.00 mol dm3 hydrochloric acid, HCl, was transferred to a beaker and solid barium carbonate, BaCO3, was added until it was in excess. (i) How many moles of acid were used in the reaction? (ii) What mass of barium carbonate, in grams, reacts with this amount of acid? The molar mass of barium carbonate is 197.3 g mol1. (iii) Why was an excess of barium carbonate used in the experiment? (1) (1) (1)12 *P42986A01224*<br /> (iv) How would you separate the barium chloride solution from the reaction mixture in part (iii)? (1)(v) The barium chloride solution was left to crystallize. The crystals were separated and dried carefully. A sample of 5.35 g of hydrated crystals, BaCl2.2H2O, which has molar mass 244 g mol1, was obtained. Calculate the percentage yield of this reaction. (vi) Give one reason why the yield of crystals is less than 100%, even when the reactants contain no impurities. (2) (1)*P42986A01324* 13 Turn over<br /> (c) The diagram below, which is not drawn to scale, shows how the lattice energy of barium chloride can be calculated using the Born-Haber cycle. Ba2+(g) + 2Cl(g)Ba2+(g) + Cl2(g)Ba+(g) + Cl2(g)Ba(g) + Cl2(g)Ba(s) + Cl2(g)Ba2+(g) + 2Cl(g)BaCl2(s)(i) Using the letters A to F, complete the table below by matching each letter to its corresponding energy change. (3) (1) 14 (ii) The energy change X is 697.6 kJ mol1. In the table, add the name of the enthalpy change which is occurring in this stage of the cycle. Energy change Lattice energy of barium chloride Enthalpy change of atomization of barium Enthalpy change of atomization of Cl2(g) to 2Cl(g) First ionization energy of barium Second ionization energy of barium Enthalpy change of formation of barium chloride Letter (cid:168)H / kJ mol1 180.0 243.4 503 965 2(348.8) = 697.6 858.6 *P42986A01424*<br /> (iii) Use the data to calculate the lattice energy of barium chloride. (2) Answer = . kJ mol1 *(iv) Lattice energies can be calculated from electrostatic theory (theoretical values) as well as by Born-Haber cycles (experimental values). What can you deduce from the fact that the experimental and theoretical values for the lattice energy of barium chloride are very close? (2)(Total for Question 18 = 18 marks) *P42986A01524* 15 Turn over<br /> BLANK PAGE 16 *P42986A01624*<br />

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