factors affecting electrolysis of aqueous solution
TRANSCRIPT
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FACTORS AFFECTING ELECTROLYSIS OF AQUEOUS SOLUTION
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Factors Affecting Electrolysis
There are three main factors that can affect the electrolysis products, there are:
Position of ions in the electrochemical series Concentration of ions andType of electrode
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Position of ions in the electrochemical series
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• The ions at the top of the list is more difficult to be discharged, but as we go down the table, they become easier to be discharged.
• For example:
Cu2+ easier to be discharged compare with H+
OH- is easier to be discharged compare with I-.
• This series of ions is called the Electrochemical Series (ES).
• The lower the ion in the electrochemical series, the easier the ion to be discharged during electrolysis.
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Electrolysis of Aqueous Sulphuric Acid
At the Cathode At the Anode
Here we have only one ion, the hydrogen, H+ (aq), and each ion gains an electron to become a hydrogen atom.
Here we have a choice of either sulphate, SO4
2- (aq), or hydroxide OH- (aq) ions.
Two of these newly formed atoms then combine to form a hydrogen gas molecule .
Hydroxide is easier to discharge, so oxygen gas is given off at the anode.
Equation:2H+ + 2e- ---> H2
Equation:4OH- ---> O2 + 2H2O + 4e-
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Concentration of Ions
• If the concentration of a particular ion is high, it will be selected to be discharged even though it is higher in the electrochemical series compares with another ion present in the solution.
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Electrolysis Of DilutedHydrochloric Acid
At the Cathode At the Anode
The hydrogen ions move to the cathode .The hydrogen ions (H+) are discharged.
Both the chloride ions (Cl-) and the hydroxide ions (OH-) migrate to the anode .The chloride ions (OH-) are preferentially discharged because of their position in ES.
Equation:2H+ + 2e- ---> H2
Equation:2Cl- ---> Cl2 + 2e-
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