13618.06R 15 Sodium hydroxide solution is used in precipitation reactions and in titrations. (a) When a sample of 175 cm3 of a 0.100 mol dm-3 solution of sodium hydroxide is added to 125 cm3 of a 0.100 mol dm-3 solution of magnesium chloride, magnesium hydroxide forms as a white precipitate. MgCl2  +  2NaOH  →  Mg(OH)2  +  2NaCl (i) Write an ionic equation, including state symbols, for this reaction. [2] (ii) Calculate the maximum mass of magnesium hydroxide which could form. Give your answer to 3 significant figures. Answer                         [4] 13618.06R (b) In a titration, 25.0 cm3 of sulfuric acid were titrated using 0.18 mol dm-3 sodium hydroxide solution. The table below shows the titration values obtained. The mean titre was calculated to be 21.2 cm3. Rough Accurate 1 Accurate 2 Initial burette reading /cm3 1.5 24.9 Final burette reading /cm3 23.4 44.5 Titre /cm3 21.3 (i) Complete the table. [3] (ii) Calculate the concentration of the sulfuric acid in g dm-3. Give your answer to an appropriate number of significant figures. Answer                         g dm-3 [4] (iii) Name a suitable indicator for this titration and state the colour change observed at the end point. Indicator: Colour change: [2] THIS IS THE END OF THE QUESTION PAPER 13618.06R 13618.06R BLANK PAGE DO NOT WRITE ON THIS PAGE Permission to reproduce all copyright material has been applied for. In some cases, efforts to contact copyright holders may have been unsuccessful and CCEA will be happy to rectify any omissions of acknowledgement in future if notified. DO NOT WRITE ON THIS PAGE SCH14/7 276813 Examiner Number For Examiner’s use only Question Number Marks Section A 1–10 Section B 11 12 13 14 15 Total Marks