4.1. Electrolysis
A subsection of Chemistry, 0620, through 4. Electrochemistry
Listing 10 of 449 questions
shows the apparatus used to electrolyse molten magnesium chloride. + – power supply unreactive gas molten magnesium Label the anode in . Name a non-metal that can be used as the anode. Name the product formed at each electrode. positive electrode negative electrode Use your knowledge of the reactivity of magnesium to suggest why an unreactive gas is blown into the electrolysis cell. Alloys of magnesium and aluminium are used to make aircraft. State the meaning of the term alloy. Magnesium reacts with hydrochloric acid. Write the formula of the ion that is present in all acids. Name the gas produced when hydrochloric acid reacts with magnesium. Dilute hydrochloric acid is added to a solution of thymolphthalein in aqueous sodium hydroxide until the acid is in excess. State the colour change of the thymolphthalein. from to Name the indicator that can be used to determine the pH of a sample of dilute hydrochloric acid. , ,
0620_s24_qp_32
THEORY
2024
Paper 3, Variant 2
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Molten calcium bromide is electrolysed. Define the term electrolysis. Name an inert metal that can be used for the electrodes. Name the product formed at each electrode. positive electrode negative electrode  Calcium reacts with water. An alkaline solution is produced. Name the ion which causes a solution to be alkaline. Choose the pH value of an alkaline solution. Draw a circle around your chosen answer. pH 1 pH 5 pH 7 pH 9 Dilute hydrochloric acid is added to a solution of litmus in alkaline solution until the acid is in excess. State the colour change of the litmus. from to ������������������������������������������������������������ Calcium carbonate is added to the blast furnace in the production of iron. Calcium carbonate breaks down when heated to produce calcium oxide and a gas that turns limewater milky. Name the gas that turns limewater milky. Name the type of chemical reaction that takes place when calcium carbonate is heated. 
0620_s24_qp_33
THEORY
2024
Paper 3, Variant 3
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This question is about the elements sodium and fluorine and the compound sodium fluoride. Sodium reacts with fluorine to form sodium fluoride. Write a symbol equation for this reaction. Some properties of sodium, fluorine and sodium fluoride are shown in Table 3.1. Table 3.1 melting point / °C boiling point / °C conduction of electricity when solid conduction of electricity in aqueous solution sodium good fluorine –220 –188 poor sodium fluoride poor good Explain why sodium conducts electricity when it is a solid. Complete the dot-and-cross diagram in of a molecule of fluorine. Show outer shell electrons only. F F  Deduce the physical state of fluorine at –200 °C. Use the data in Table 3.1 to explain your answer. physical state explanation  Explain in terms of structure and bonding why sodium fluoride has a much higher melting point than fluorine. Dilute aqueous sodium fluoride undergoes electrolysis. Hydrogen is produced at the cathode. State what is meant by the term electrolysis. Write an ionic half-equation for the production of hydrogen at the cathode. 
0620_s24_qp_41
THEORY
2024
Paper 4, Variant 1
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Lead(bromide, PbBr2, is an insoluble salt and is made by precipitation. Name two aqueous solutions that produce a precipitate of lead(bromide when they are mixed.  Describe how to produce a pure sample of lead(bromide from the mixture of aqueous solutions in . Write an ionic equation for the precipitation reaction which produces lead(bromide. Include state symbols. When iron(sulfate crystals are heated strongly, sulfur dioxide gas is given off. Describe a test for sulfur dioxide gas. test observations  Complete the equation for the thermal decomposition of hydrated cobalt(nitrate. 2Co(NO3)2•4H2O → CoO + NO2 + O2 + H2O Hydrated cobalt(sulfate, CoSO4•xH2O, produces water when it is heated. CoSO4•xH2O→ CoSO4+ xH2OA student does an experiment to determine the value of x in CoSO4•xH2O. step 1 The student weighs a sample of hydrated cobalt(sulfate. step 2 The student heats the sample of hydrated cobalt(sulfate. step 3 The student weighs the remaining solid after heating. Describe what else the student should do to ensure that all the water has been given off. No other substances are required. In an experiment, 1.405 g of CoSO4•xH2O is heated until all the water is given off. The mass of CoSO4 that remains is 0.775 g. [Mr: CoSO4, 155; H2O, 18] Determine the value of x using the following steps. ● Calculate the number of moles of CoSO4 that remains.  mol ● Calculate the mass of H2O given off.  g ● Calculate the number of moles of H2O given off.  mol ● Determine the value of x.  x =  
0620_s24_qp_41
THEORY
2024
Paper 4, Variant 1
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This question is about elements and compounds. Some properties of graphite, oxygen and carbon monoxide are shown in Table 3.1. Table 3.1 melting point / °C boiling point / °C conduction of electricity when solid graphite good oxygen –218 –183 poor carbon monoxide –199 –191 poor Explain why graphite conducts electricity when solid. Complete the dot-and-cross diagram in of a molecule of oxygen. Show outer shell electrons only. O O  Deduce the physical state of carbon monoxide at –195 °C. Use the data in Table 3.1 to explain your answer. physical state explanation  Explain in terms of structure and bonding why graphite has a much higher melting point than carbon monoxide. Potassium reacts with chlorine to form potassium chloride. Write a symbol equation for this reaction. A dilute aqueous solution of potassium chloride undergoes electrolysis. Oxygen is produced at the anode. State what is meant by the term electrolysis. Write an ionic half-equation for the production of oxygen at the anode. 
0620_s24_qp_43
THEORY
2024
Paper 4, Variant 3
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