Beatty 17.5_ELECTROCHEM_(W5)_Review 2023_Answers4E1

1 Beatty Secondary School Science Department (Chemistry Unit) Chemistry 6092 Name: ___________________________________ ( ) Date: _______________ Class: 4E___ TOPIC: ELECTROCHEMISTRY (WORKSHEET 5) – REVIEW Multiple-Choice Questions 1 Element X is extracted by the electrolysis of a molten compound of elements X and Y. The electrode reactions are as shown. What could be the identity of the compound? positive electrode: 2Y2− → Y2 + 4e− negative electrode: X2+ + 2e− → X A aluminium oxide B magnesium oxide C calcium chloride D potassium chloride ( B ) 2 A metal can be obtained by the electrolysis of its molten chloride. The table shows properties of the metal and its chloride. substance melting point / °C boiling point / °C density / gcm−3 metal 328 1750 11 metal chloride 534 950 4.5 In which state will the metal be formed in electrolysis? A as a solid below the molten chloride B as a liquid below the molten chloride C as a solid on the surface of the molten chloride D as a liquid on the surface of the molten chloride ( B ) 3 Which of the following involves the largest number of electrons for complete discharge during electrolysis? A 4 mol of Al3+ ions B 6 mol of Cu2+ ions C 5 mol of OH− ions D 7 mol of O2− ions ( D ) 4 Dilute sulfuric acid was electrolysed using inert electrodes. What volumes (at r.t.p) of hydrogen and oxygen were formed by the passage of 1 mole of electrons? volume of hydrogen / dm3 volume of oxygen / dm3 A 24 12 B 12 6 C 6 12 D 12 24 ( B )

2 5 Processes 1, 2 and 3 each involve the movement of charged particles. Which process(es) involve(s) the movement of ions? A process 1 only B process 2 only C process 1 and 2 D process 2 and 3 ( D ) 6 Aluminium is obtained by electrolysis of molten aluminium oxide. Which statement about the electrolysis is correct? A Aluminium ions are oxidised to aluminium at the negative electrode. B Aluminium ions are oxidised to aluminium at the positive electrode. C Aluminium ions are reduced to aluminium at the negative electrode. D Aluminium ions are reduced to aluminium at the positive electrode. ( C ) 7 What happens to the ions that move to the negative electrode during electrolysis of molten potassium iodide? A Ions are reduced. B Ions form molecules. C Ions increase in charge. D Ions release electrons. ( A ) 8 In the electrolysis of molten sodium chloride, 46 g of sodium is formed at the cathode. How many moles of chlorine gas are formed at the anode? A 0.5 mol B 1.0 mol C 2.0 mol D 4.0 mol ( B )

3 9 The following three different solutions were electrolysed using inert electrodes. 1 aqueous sodium chloride 2 concentrated hydrochloric acid 3 dilute sulfuric acid Which solution(s) produce(s) hydrogen at the cathode? A 1 only B 1 and 2 only C 1, 2