Asia-Pacific Forum on Science Learning and Teaching, Volume 17, Issue 1, Article 8 (Jun., 2016) Anita Yung Li BONG and Tien Tien LEE Form four students’ misconceptions in electrolysis of molten compounds and aqueous solutions Previous Contents Next

Appendix

Appendix A: open-ended electrochemistry assessment

Question 1

A compound is electrolyzed using carbon electrodes as shown in figure below:

a) Identify which electrode is anode and cathode?

Anode: ______________________________
Cathode: _____________________________

b) How would you determine anode and cathode of electrode?

Anode:
______________________________________________________________
Cathode:
______________________________________________________________

c) Does polarity of batteries affect the position of anode and cathode in the diagram above?

______________________________________________________________

d) Can carbon electrode take place in this electrolysis reaction? Why?

______________________________________________________________

e) i) Which ions move to electrode X and Y during the electrolysis process?

Electrode X: ______________________________________________________
Electrode Y: ______________________________________________________

ii) Explain your answer in e (i).

Electrode X _____________________________________________________________

Electrode Y
_____________________________________________________________

f) Write the half equation for anode and cathode.

Anode:   ____________________________________________________________
Cathode: ____________________________________________________________

g) i) If the electrolyte is changed to aqueous potassium iodide, what are the ions involved in electrolysis process?

_____________________________________________________________

ii) What ion is selectively discharged to anode and cathode?

Anode:    ____________________________________________________________
Cathode: ____________________________________________________________ 

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Question 2

0.05 mol dm^-3 copper (II) chloride solution is electrolyzed by using carbon electrodes as shown in the diagram below.

a) i) Which electrode is anode and which is cathode?

Anode:   ______________________________
Cathode: ______________________________

ii) Based on your answer in a (i), how do you assign anode and cathode for electrode X and Y?

Anode:   ______________________________________________________________
Cathode: ______________________________________________________________

b) i) What ions are present in the electrolysis process above?

______________________________________________________________

ii) What are the sources for the ions you have listed in b (i)?

______________________________________________________________

c) Does water takes place in this reaction?

______________________________________________________________

d) i) Which ions move to anode and cathode?

Anode: ______________________________________________________________
Cathode: ______________________________________________________________

ii) Explain how you identify the ions which move to anode and cathode.

Anode: ________________________________________________________
Cathode:
______________________________________________________________

e) i) Write the half equations for reactions at electrode X and electrode Y

Anode: ______________________________________________________________
Cathode: ______________________________________________________________

ii) Explain how do you choose which ions are selectively discharged at anode and cathode based on the half equation you have written in e (i).

Anode: ______________________________________________________________

Cathode:
______________________________________________________________

f) i) If 0.05 mol dm^-3 of copper (II) chloride solution is replaced with 2 mol dm^-3 of copper (II) chloride solution, predict what will be observed at anode.

______________________________________________________________

ii) Explain your answer.

______________________________________________________________

iii) Write a half equation for the observation in f (i).

______________________________________________________________

g) i) If both of the carbon electrodes are replaced with 2 copper electrodes, what can you observe on physical appearances of the 2 copper electrodes after the electrolysis process?

______________________________________________________________

ii) Explain your answer.

______________________________________________________________

iii) Write half equation for anode and cathode to support your answer in g (i) and g (ii).

Anode:   _____________________________________________________________
Cathode: _____________________________________________________________