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MODULE • Chemistry Form 4

(i) Concentrated hydrochloric acid solution, using carbon electrodes
Larutan asid hidroklorik pekat menggunakan elektrod karbon
Anode / Anod: Cl – Cathode / Katod: H +
(ii) Concentrated potassium iodide solution, using carbon electrodes
Larutan kalium iodida pekat menggunakan elektrod karbon
Anode / Anod: l – Cathode / Katod: K +
(iii) Concentrated sodium chloride solution, using carbon electrodes
Larutan natrium klorida pekat menggunakan elektrod karbon
Anode / Anod: Cl – Cathode / Katod: H +

–3
–3
(c) Complete the following table for the electrolysis of 0.001 mol dm hydrochloric acid and 2.0 mol dm hydrochloric
acid, using carbon electrodes.
Lengkapkan jadual berikut bagi elektrolisis asid hidroklorik 0.001 mol dm dan asid hidroklorik 2.0 mol dm menggunakan elektrod
–3
–3
karbon.
Set-up of apparatus
Susunan radas
Carbon electrodes
Hydrochloric acid

+
Equation of electrolyte ionisation HCl H + Cl –
Persamaan pengionan elektrolit H 2 O H + OH –
+
Electrolyte 0.001 mol dm of HCl 2.0 mol dm of HCl
-3
-3
Elektrolit HCl 0.001 mol dm –3 HCl 2.0 mol dm –3
Ions that are attracted to the cathode H + H +
Ion bergerak ke katod
Half equation at the cathode 2H + 2e H 2H + 2e H
+
+
Persamaan setengah di katod 2 2
Observation at cathode Gas bubbles are released. Gas bubbles are released.
Pemerhatian di katod
Confirmatory test at cathode (method – Insert a burning wooden splinter into – Insert a burning wooden splinter into
and observations) the test tube. the test tube.
Ujian pengesahan (kaedah dan pemerhatian) – A ‘Pop’ sound is produced. – A ‘pop’ sound is produced.
Name the products at the cathode Hydrogen gas Hydrogen gas
Nama hasil di katod
Ions that are attracted to the anode Cl , OH – Cl , OH –
–
–
Ion bergerak ke anod
Half equation at the anode 4OH 2H O + O + 4e 2Cl Cl + 2e
–
–
Persamaan setengah di anod 2 2 2
Observations at anode / Pemerhatian Gas bubbles are released. Greenish yellow gas is released.
Confirmatory test at anode (method – Insert a glowing wooden splinter into – A damp blue litmus paper placed near
and observations) the test tube. the mouth of the test tube.
Ujian pengesahan (kaedah dan pemerhatian) – Glowing wooden splinter is lighted up. – The gas changed the damp blue litmus
paper to red and then bleached it.
Name the product at the anode Oxygen gas Chlorine gas
Nama hasil di anod
The concentration of hydrochloric acid Concentration of hydrochloric acid Concentration of hydrochloric acid
after a while and explanation increases . Hydrogen gas is released at decreases . Hydrogen gas released at
Kepekatan elektrolit selepas beberapa ketika the cathode and oxygen gas is released the cathode and chlorine gas released at
dan terangkan
at the anode. Water decomposed to the anode. Concentration of chloride
oxygen gas and hydrogen gas. ions decreases.
Kepekatan asid hidroklorik bertambah . Kepekatan asid hidroklorik berkurang .
Gas hidrogen dibebaskan di katod dan gas Gas hidrogen dibebaskan di katod dan gas
oksigen dibebaskan di anod. Air terurai kepada klorin dibebaskan di anod. Kepekatan ion
gas oksigen dan gas hidrogen . klorida berkurang.

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