ELECTROCHEMISTRY
PRE-TEST
DO NOT OPEN THIS QUESTION BOOKLET UNTIL YOU ARE INFORMED
INFORMATION FOR CANDIDATES
1. This question paper consists of 12 printed pages.
2. There are 2 questions in this booklet.
3. Answer all questions in the space given.
1. A student has carried out an experiment of electrolytic cell using the apparatus as shown in the figure above.
a) Determine the electrode which becomes:
(i) anode: ______
(ii) cathode: ______
b) How do you identify the anode and cathode in this cell?
______
c) (i) Draw the direction of the flow of electrons in the cell above when electrolysis process is occurring.
(ii) Give a reason for your answer in(c) (i). ______
d) Imagine that you can see the particles in the electrolyte. Draw and label all the ions that exist in the beaker at the A area before the reaction begins.
e) Name the ions that move and accumulated at
(i) electrode carbon A:
______
(ii) electrode carbon B:
______
f) Give a reason for your answer in (e) (i) and (e) (ii).
______
g) Write the ionic equations (half equations) showing the reactions taking place at the
(i) anode: ______
(ii) cathode: ______
h) Give a reason for your answer in (g) (i) and (g) (ii).
______
i) (i) Predict any colour change of the solution that may occur in
the beaker after electrolysis has been carried out for 50 minutes?
______
______
(ii) State a reason for your answer in (i) (i).
______
______
j) Draw the amount of Cu2+ ions in the beaker at the B area before and after electrolysis has been carried out for 50 minutes.
k) The experiment is repeated using copper electrodes. State what will be observed
(i) at the anode:
______
(ii) Reason:
______
______
(iii) at the cathode:
______
______
(iv) Reason:
______
______
(v) to the colour of the copper (II) chloride solution:
______
______
(vi) Reason:
______
______
l) The experiment is repeated using concentrated copper (II) chloride solution. State what will be observed
(i) at the anode:
______
______
(ii) Reason:
______
______
(iii) at the cathode:
______
______
(iv) Reason:
______
______
(v) to the colour of the copper (II) chloride solution:
______
______
(vi) Reason:
______
______
2. Figure above shows the arrangement of apparatus in an electrochemical cell experiment.
a) Determine the metal which becomes:
(i) positive terminal: ______
(ii) negative terminal: ______
b) How do you identify the positive terminal and negative terminal in this cell?
______
______
c) (i) Draw the direction of the flow of electrons in the cells above.
(ii) Give a reason for your answer in (c) (i).
______
______
d) Imagine that you can see the particles in the electrolyte. Draw and label all the ions that exist in the copper beaker and lead beaker before the reaction starts.
e) Name the ions that move and accumulated at
(i) copper metal:
______
(ii) lead metal:
______
f) Give a reason for your answer in (e) (i) and (e) (ii).
______
______
g) Write the ionic equations (half equations) showing the reactions taking place at the
(i) anode: ______
(ii) cathode: ______
h) Give a reason for your answer in (g) (i) and (g) (ii).
______
______
i) At the end of the process, what will be observed at the
(i) positive terminal:
______
(ii) negative terminal:
______
j) State a reason for your answer in (i) (i) and (i) (ii).
______
______
k) What is the function of the salt bridge?
______
______
l) (i) If the salt bridge in the diagram is replaced with a copper wire, state what will happen to the voltage reading?
______
______
(ii) Give a reason to your answer in (l) (i).
______
m) (i) If the lead and copper metals are replaced with two similar carbon rods, state what will happen to the voltage reading?
______
______
(ii) Give a reason to your answer in (m) (i).
______
______