Beatty 17.2_ELECTROCHEM_(W2)_2023_Answers

1 Beatty Secondary School Science Department (Chemistry Unit) Chemistry 6092 Name: ___________________________________ ( ) Date: _______________ Class: 4E___ TOPIC: ELECTROCHEMISTRY (WORKSHEET 2) – ELECTROLYSIS OF AQUEOUS & CONCENTRATION SOLUTIONS Learning Objectives: (a) Apply the idea of selective discharge based on (i) cations: linked to the reactivity series (ii) anions: halides, hydroxides and sulfates [e.g. aqueous copper( II) sulfate and dilute sodium chloride solution (as essentially the electrolysis of water)] (iii) concentration effects (as in the electrolysis of concentrated and dilute aqueous sodium chloride) (In all cases above, inert electrodes are used.) (b) Predict the likely products of the electrolysis of an aqueous electrolyte, given relevant information. (c) Construct ionic equations for the reactions occurring at the electrodes during the electrolysis, given relevant information. Multiple-Choice Questions 1 Rubidium is above sodium in the reactivity series. What is formed when concentrated rubidium chloride is electrolysed? cathode (−) anode (+) A chlorine hydrogen B hydrogen rubidium C hydrogen chlorine D rubidium chlorine ( C ) 2 A solid deposit of element R is formed at the cathode(−ve) when an aqueous solution containing ions of R is electrolysed. Which statement about element R must be correct? A R forms negative ions. B R ions gain electrons at the cathode. C R ions lose electrons at the cathode. D R is above hydrogen in the reactivity series. ( B ) 3 Dilute sulfuric acid is electrolysed using inert electrodes. Which equation represents the reaction at the anode (+ve)? A O22− → O2 + 2e− B 2H+ + 2e− → H2 C 4OH− → 2H2O + O2 + 4e− D SO42− → SO2 + O2 + 2e− ( C )

2 4 In which line in the table is all the information correct? reaction at electrode electrode product A 2X− → X2 + 2e− cathode metal B X+ + e− → X anode metal C 2X− → X2 + 2e− anode non-metal D X+ + e− → X cathode non-metal ( C ) 5 Apparatus is set up as shown in the diagram. What occurs at electrode X? A Chloride ions are oxidised. B Chloride ions are reduced. C Nickel ions are oxidised. D Nickel ions are reduced. ( A ) 6 Which statement about the electrolysis of concentrated aqueous sodium chloride using inert electrodes is correct? A Chlorine is released at the cathode. B Oxygen is released at the cathode. C Sodium is released at the cathode. D The pH of the electrolyte increases. ( D ) 7 Four different conditions under which sodium chloride is electrolysed using inert electrodes are listed. 1 concentrated aqueous sodium chloride 2 dilute aqueous sodium chloride 3 molten sodium chloride 4 solid sodium chloride Under which conditions is a green gas formed? A 1 and 2 B 1 and 3 C 3 and 4 D 3 only ( B )

3