Copy of MGS Chemistry P2

Page 2 of 28 Methodist Girls’ School Chemistry Paper 2 Sec 4 Preliminary Examination 2024 Section A (70 marks) Answer all the questions. 1 (a) Some chemical equations, A to F, are shown. A Ba 2+ (aq) + SO42- (aq) → BaSO4(s) B CO32- (aq) + 2H+ (aq) → CO2 (g) + H2O (l) C Ag + (aq) + I- (aq) → AgI (s) D H + (aq) + OH- (aq) → H2O (l) E 2I- (aq) + Br2 (aq) → I2 (aq) + 2Br- (aq) F NH4+ (aq) + OH- (aq) → H2O (l) + NH3 (aq) Answer the following questions using the equations. Each equation may be used once, more than once or not at all. Give the letter, A to F, for the equation which shows: (i) the formation of a gas that turns moist red litmus paper blue [1] (ii) a reaction that forms a white precipitate [1] (iii) a displacement reaction [1] (b) Ammonium ion, NH4+, is a polyatomic ion. Ammonium ion is formed when ammonia reacts with hydrogen ion. The nitrogen atom in ammonia contributes and donates a pair of valence electrons to one hydrogen ion to form a covalent bond. Draw a ‘dot and cross’ diagram to show the covalent bonding in ammonium ion using the key provided. Show outer electrons only. [2] [Total: 5] Key: x : electron of hydrogen • : electron of nitrogen

Page 3 of 28 Methodist Girls’ School Chemistry Paper 2 Sec 4 Preliminary Examination 2024 2 Copper is a transition element. The flowchart in Fig. 2.1 shows how copper can be made from copper (II) carbonate, either in the industry, or on a small scale in the laboratory. Copper(II) carbonate, CuCO3 Copper(II) oxide, CuO Copper, water and impurities Copper, Cu Fig. 2.1 (a) (i) Identify gas X. [1] (ii) State the type of reaction that takes place when copper(II) oxide is heated with carbon. [1] (iii) Write an equation for the reaction in (a)(ii). [1] Shake solids left behind with water Heat Heat with carbon Solid copper sinks to the bottom. Pour off water and impurities to leave copper. Put wet copper in an oven to dry gas X water and impurities

Page 4 of 28 Methodist Girls’ School Chemistry Paper 2 Sec 4 Preliminary Examination 2024 (b) Jane uses the procedure in the flowchart to make copper in the laboratory. She uses the following graph shown in Fig. 2.2 to predict the theoretical yield of copper. (i) Explain why the line on the graph in Fig. 2.2 starts at 0 on both axes. [1] (ii) Jane wants to make a theoretical yield of 40.0 g of copper. Using the graph in Fig. 2.2 , predict the starting mass of copper(II) carbonate she shoul