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Saturday, June 25, 2011

Chemistry Form 4: Chapter 6 - Electrolysis of Concentrated of Sodium Chloride Solution


Electrolysis of dilute sodium chloride solution
Electrolysis of concentrated sodium chloride solution
At
anode :








Anions :  OH-   and   Cl-

OH- ions are selectively discharge according to the position of ions in the Electrochemical Series, ES. 

Gas bubbles are formed which lighted up a glowing wooden splinter. This gas is oxygen.

4OH- ---> 2 H2O  +  O2   +  4e


At
anode :








Anions :  OH-   and   Cl-

Cl- ions are discharged instead of OH- because of their higher concentration in the electrolyte.

A greenish-yellow gas with a pungent and choking smell is released. The gas turns the blue litmus paper red and then white.

2Cl-  --->  Cl2    +     2e

At cathode:
Cations :  H+   dan   Na+

H+ ions are selectively discharge according to the position of ions in the ES.

Gas bubbles are formed. When a lighted wooden splinter is placed near the mouth of   the test tube, a ‘pop’ sound is produced.  Hydrogen gas is produced

        2H+   +   2e ---> H2
       
At cathode:
Cations :  H+   dan   K+

H+ ions are selectively discharge according to the position of ions in the ES.

Gas bubbles are formed. When a lighted wooden splinter is placed near the mouth of the test tube, a ‘pop’ sound is produced.  Hydrogen gas is produced

    2H+   +   2e ---> H2


4 comments:

Anonymous said...

Sorry sir..if 0.5M NaCl is considered as concentrated or dilute? We followed electrochemical series or select higher concentrated ion for 0.5M NaCl? OH- or Cl- will be selected? Thank you sir.

Anonymous said...

ah boy please dont call me sir!

Anonymous said...

good job

Jocelyn Wong said...

Hai cikgu wong, may i ask for the overall equation?