Page 103 - Nilam_Publication_module_Chemistry_Form.pdf

Chemistry Form 4 • MODULE

Observation and half equation / Pemerhatian dan persamaan setengah:
Electrodes Observation Conf rmatory test Half equation
Elektrod Pemerhatian Ujian pengesahan Persamaan setengah
Cathode Brown solid deposited Cu + 2e Cu
2+
–
–
Anode Gas bubbles are released – Insert the glowing wooden splinter into the test 4OH 2H O + O + 4e
2
2
tube.
– The glowing wooden splinter is lighted up.
4 Copper(II) sulphate solution is electrolysed using copper electrodes.
Larutan kuprum(II) sulfat dielektrolisis dengan menggunakan elektrod kuprum.
(a) Write the formula of all the anions present in the solution / Tuliskan formula semua anion yang terdapat dalam larutan itu.
SO , OH
–
2–
4
(b) Write the half equation for the reaction at the / Tuliskan persamaan setengah untuk tindak balas di
2+
(i) anode / anod : Cu Cu + 2e
2+
(ii) cathode / katod : Cu + 2e Cu
(c) (i) From your observations, what happen to the intensity of the blue colour of the copper(II) sulphate solution
during electrolysis?
Daripada pemerhatian anda, nyatakan apakah yang berlaku ke atas keamatan warna biru larutan kuprum(II) sulfat semasa
proses elektrolisis?
The intensity of the blue colour of copper(II) sulphate remains unchanged.

(ii) Explain your answer / Jelaskan jawapan anda.
The number of copper(II) ions become copper atoms at the cathode is equal to the number of copper atoms
become copper(II) ions at the anode.
(d) If the experiment is repeated with the copper electrodes being replaced by carbon electrodes, state the name of the
products formed at the
Jika eksperimen diulangi dengan menggantikan elektrod kuprum dengan elektrod karbon, namakan hasil yang terbentuk di
(i) anode / anod: Oxygen (ii) cathode / katod: Copper
5 The diagram below shows the set-up of apparatus of an electrolytic cell.
Rajah di bawah menunjukkan susunan radas bagi sel elektrolisis.

Carbon electrode P Carbon electrode Q
Elektrod karbon P Elektrod karbon Q

Copper(II) nitrate solution
Larutan kuprum(II) nitrat
(a) Write the formula of all ions present in copper(II) nitrate solution.
Tuliskan formula semua ion yang hadir dalam larutan kuprum(II) nitrat.
–
Cu , NO , H and OH .
2+
+
–
3
(b) Write half equation for the reaction at / Tuliskan persamaan setengah di:
2+
electrode P / elektrod P : Cu + 2e Cu
–
electrode Q / elektrod Q : 4OH 2H O + O + 4e
2
2
(c) (i) What is the colour of copper(II) nitrate / Apakah warna larutan kuprum(II) nitrat?
Blue
(ii) What happens to the intensity of the colour of copper(II) nitrate solution? Explain your answer.
Apakah yang berlaku kepada keamatan warna larutan kuprum(II) nitrat? Jelaskan jawapan anda.
The intensity of the blue colour of copper(II) nitrate decreases. The concentration of Cu decreases because
2+
copper(II) ions receive electrons to form copper atom at the cathode.

101
Nilam Publication Sdn. Bhd.

05-Chem F4 (3P).indd 101 12/9/2011 5:56:30 PM