XMS SEC 3 WA3 2022 QP

3 6092/Chemistry/2022 Term 3 Weighted Assessment Section A Answer all questions. Write your answers in the boxes provided at the end of the Section. 1 Copper(II) sulfate is made by reacting an excess of copper(II) oxide with dilute sulfuric acid. The excess copper(II) oxide is then removed from the solution. Why is excess oxide added and how is the excess oxide removed? Why add excess oxide How to remove excess oxide A To use up all the acid By filtration B To use up all the acid By heating C To produce water By filtration D To produce water By heating 2 The graph shows how the pH of soil in a field changes over time. At which point was the soil neutral? 3 Given a supply of magnesium carbonate, zinc carbonate, dilute sulfuric acid and aqueous sodium hydroxide, how many different salts can be prepared? A 1 B 2 C 3 D 4

4 6092/Chemistry/2022 Term 3 Weighted Assessment 4 The diagram shows two experiments on a powdered oxide. In both experiments, the powdered oxide reacts and dissolves. What could the oxide be? powdered oxide reason A potassium oxide potassium oxide is basic B silicon dioxide silicon dioxide is acidic C sodium oxide sodium oxide is neutral D zinc oxide zinc oxide is amphoteric powdered oxide dilute sulfuric acid powdered oxide aqueous sodium hydroxide

5 6092/Chemistry/2022 Term 3 Weighted Assessment 5 Ammonium sulfate is heated with solution X and ammonia gas is given off. A piece of moist red litmus paper and a piece of moist blue litmus paper are held in the gas. What is solution X and what will be the colour change of the litmus paper? solution X colour change of litmus paper A an acid blue to red B an acid red to blue C an alkali blue to red D an alkali red to blue Question 1 2 3 4 5 Answer

6 6092/Chemistry/2022 Term 3 Weighted Assessment For Examiner’s Use Section B Answer all questions. Write your answers in the spaces provided. 6 (a) Explain, in terms of ionisation, the difference between a strong and a weak acid. …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… [2] (b) A sample of an acid contains 0.16 g of hydrogen, 0.96 g of carbon and 1.28 g of oxygen. (i) Determine the empirical formula of this acid. [2] (ii) The relative molecular mass of the acid is 60. Deduce the molecular formula of the acid. [1] [Total: 5]

7 6092/Chemistry/2022 Term 3 Weighted Assessment For Examiner’s Use 7 The table shows information on some salts and products that contain them. name of salt formula of salt name of one compound to make salt name of other compound to make salt use of salt silver chloride AgCl hydrochloric acid in photographic film potassium nitrate KNO3 potassium hydroxide making fertilisers barium sulfate BaSO4 barium nitrate medical tracer sodium chloride NaCl hydrochloric acid food additive lead sulfate PbSO4 lead nitrate in a car battery (a) Complete the table by filling in the missing information. [5] (b) Name two salts in the table that can be made by (i) a titration method, ……………………………………….and ………………………………………. [1] (ii) a precipitation method. ……………………………………….and ………………………………………. [1] (c) Using the formulae of the salts in the table, show by calculation that 1 kg of barium sulfate contains a larger mass of sulfate ions than 1 kg of lead sulfate. [2] (d) Write an ionic equation for the reaction used to make any one of the salts in the table. [1] [Total: 10]

8 6092/Chemistry/2022 Term 3 Weighted Assessment For Examiner’s Use Section C Answer all questions. Write your answers in the spaces provided. 8 (a) To determine the pH of a sample of farm soil, drops of three indicators below were added to separate parts of the sample. The colours observed are shown in the results table. Experimental results indicator methyl yellow methyl red phenolphthalein colour observed yellow red colourless Indicator colour ranges Plant response to soil pH Plant soil pH range for optimal growth carrot 5.5 – 6.8 chrysanthemum 6.0 – 6.3 hydrangea blue 4.0 – 5.0 hydrangea white 6.5 – 8.0 potato 5.0 – 5.7 Using the data given, estimate the pH of the soil and select the plant that will grow well at the current soil pH. …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… [2]

9 6092/Chemistry/2022 Term 3 Weighted Assessment For Examiner’s Use (b) Acid rain, a result of air pollution, sometimes fall on farms and lakes. Limestone in the form of c alcium carbonate is often used to neutralise the H+ ions in the acidic soil or water. CaCO3 + 2H+ → Ca2+ + CO2 + H2O A lake is found to contain 10,500 moles of H+ ions. Calculate the mass of calcium carbonate needed to react with all of the H+ ions in the lake. [2] [Total: 4]

10 6092/Chemistry/2022 Term 3 Weighted Assessment For Examiner’s Use 9 General Equations The equations for the neutralisation reaction between a metal hydroxide (base) and hydrochloric acid for the first three elements in Group I are: LiOH + HCl → LiCl + H2O NaOH + HCl → NaCl + H2O KOH + HCl → KCl + H2O The general equation for such a reaction between a Group I metal hydroxide and hydrochloric acid may be written as: MOH + HCl → MCl + H2O A general equation is useful because it shows the mole ratios of the reactants and products in that reaction for all the elements in the same group. The general equation for the neutralisation reaction between a Group II metal hydroxide and hydrochloric acid may be written as: M(OH)2 + 2HCl → MCl2 + 2H2O The general equations for the Group I and II neutralisation reactions are different because the charges on the metal ions (and so the formulae of the hydroxides) are different. Group II metal carbonates decompose when heated, producing carbon dioxide. For example, BeCO3 → BeO + CO2 MgCO3 → MgO + CO2 CaCO3 → CaO + CO2 Group II metal carbonates also react with acids to produce carbon dioxide. For example, BeCO3 + 2HCl → BeCl2 + H2O + CO2 MgCO3 + 2HCl → MgCl2 + H2O + CO2 CaCO3 + 2HCl → CaCl2 + H2O + CO2 (a) Why are the general equations for the neutralisation reaction of Group I and II metal hydroxides different? …………………………………………………………………………………………… …………………………………………………………………………………………… [1] (b) Using the passage and the Periodic Table, write an equation for the reaction of (i) rubidium hydroxide with hydrochloric acid, ……………………………………………………………………………………. [1] (ii) strontium hydroxide with hydrochloric acid. ……………………………………………………………………………………. [1]

11 6092/Chemistry/2022 Term 3 Weighted Assessment For Examiner’s Use (c) Construct the general equation for (i) the decomposition of a Group II metal carbonate, ……………………………………………………………………………………. [1] (ii) the reaction of a Group II metal carbonate with hydrochloric acid. ……………………………………………………………………………………. [1] (d) A student weighs out 4.86 g of an unknown Group II metal carbonate . To determine its identity, he reacted it fully with hydrochloric a