OCR 2023 Chemistry B H033/02: Chemistry in depth AS Level Question Paper & Mark Scheme (Merged)

1 This question is about Group 2 compounds. Group 2 hydroxides can be used to neutralise acidity in a variety of contexts. Magnesium hydroxide may be used to neutralise excess stomach acidity and calcium hydroxide may be used to neutralise acidity in soils. The hydroxides are formed when the oxides react with water. (a) Write an equation to show the ions formed when calcium oxide reacts with water. [1] (b) A student shakes a small amount of magnesium oxide in a test tube with water. A white suspension is formed. The student then adds dilute hydrochloric acid, drop by drop with shaking, until no further changes are seen. Describe how the appearance of the contents of the test tube changes during the addition of the acid. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [2] (c) Barium chloride solution is used to test for the presence of sulfate ions in solution. Write an ionic equation for this test. Include state symbols. [2] 3 OCR 2023 Turn over 4 OCR 2023 (d) A student is provided with a solid sample of an unknown Group 2 hydroxide, X(OH)2 . The student describes how 250cm3 of a solution of this solid is made up in a volumetric flask. Step 1 The mass of a we