02_2024_CCKSS_4E_Prelim_CHEM_P2

2 Section A Answer all questions. 1 Use the list of substances to answer the questions. Each option may be used once, more than once or not at all. ammonium chloride barium sulfate lead (II) fluoride potassium carbonate potassium iodide potassium manganate(VII) sodium chloride (a) Which substance reacts with methanoic acid to produce a gas? …………………………………………………………………………………………….. [1] (b) Which substance is used to test for an oxidising agent? …………………………………………………………………………………………….. [1] (c) Which substance, when warmed with aqueous sodium hydroxide, produces a gas that turns moist red litmus blue? …………………………………………………………………………………………….. [1] (d) Which substance reacts with aqueous chlorine to form a brown solution? …………………………………………………………………………………………….. [1] (e) Which substance produces a pale yellow vapour when electricity is passed through its molten state? …………………………………………………………………………………………….. [1] (f) Which two salts cannot be prepared by titration method? ……………………………………… and …...………………………………………….. [1] [Total: 6]

3 2024 / S4 / CHEM / PRELIM / P2 2 Crystals of a salt produced was found to have the following composition by mass: 31.5% K, 25.6% Cu and Cl. (a) Deduce the empirical formula of the salt crystal formed. Show your working. Empirical formula: ……………………………….. [3] (b) (i) The ion of an isotope of copper has the formula 𝐶𝑢!"!#$$. Complete the table with information about this ion. subatomic particles number of subatomic particles protons neutrons electrons [1] (ii) Describe a chemical reaction that can be carried out to identify 𝐶𝑢!"!#$$. Include relevant observations in your answer. …………………………………………………………………………………………….. …………………………………………………………………………………………….. ……………………………………………………………………………………… [2] [Total: 6]

4 2024 / S4 / CHEM / PRELIM / P2 3 Calcium carbide, CaC2, is an ionic compound. This compound is commonly used in industries for the manufacture of fertilisers and in steelmaking. Calcium carbide and carbon monoxide is produced when quicklime, CaO, reacts with carbon at high temperature. (a) Explain, in terms of structure and bonding, why there is a need to carry out this reaction at a high temperature. …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………….. [3] (b) Write a balanced chemical equation, with state symbols, for this reaction. …………………………………………………………………………………………….. [2] (c) Calculate the percentage purity of a sample of quicklime when 8 g of quicklime is reacted with carbon to produce 2400 cm3 of carbon monoxide at room temperature and pressure. percentage purity: ………………………………….% [3] [Total:8]

5 2024 / S4 / CHEM / PRELIM / P2 4 Barium hydroxide is placed in a beaker. Ammonium chloride is then added into the be