Class 10 Science - ICSE-CHEMISTRY
Electrolysis
The Electrolysis chapter in Class 10 ICSE Chemistry explores the chemical effects of electric current, where direct current is passed through an electrolyte to cause chemical decomposition. Students learn about non-electrolytes, strong and weak electrolytes, and the preferential discharge of ions at electrodes. Key processes covered include the electrorefining of copper and electroplating, which have massive industrial applications. For ICSE board exams, mastering this chapter requires understanding specific observations at the anode and cathode during the electrolysis of molten lead bromide, acidified water, and aqueous copper sulfate using active and inert electrodes.
Start Learning FreeKey Concepts
Electrolyte vs Non-electrolyte
Electrolytes are substances that conduct electricity in molten or aqueous state and undergo chemical decomposition. Non-electrolytes do not conduct electricity and remain molecular in solution.
Preferential Discharge of Ions
When multiple ions migrate to an electrode, only one is discharged based on its position in the electrochemical series, concentration, and the nature of the electrode.
Electroplating
The process of depositing a thin layer of a superior metal over a cheaper metal or object using electricity for protection against corrosion or for aesthetic appeal.
Electrorefining
The purification of impure metals, such as blister copper, by making the impure metal the anode and a pure strip the cathode in a suitable metal salt solution.
Oxidation and Reduction at Electrodes
Oxidation (loss of electrons) always takes place at the anode, while reduction (gain of electrons) always takes place at the cathode during electrolysis.
Important Formulas
Board Exam Info
In ICSE Chemistry (Science Paper 2), the Electrolysis chapter typically carries around 8 to 12 marks. Questions frequently appear as chemical equations for reactions at electrodes, observations during electrolysis (color changes, gases evolved), definitions of electrochemical terms, and descriptive questions on electroplating and electrorefining.
Frequently Asked Questions
Why does pure water not conduct electricity while acidified water does?
Pure water is a poor conductor because it undergoes self-ionization to a very small extent. Adding a little acid introduces mobile hydrogen and sulfate ions that carry the electric current.
Why is the anode made of impure copper during the electrorefining of copper?
The impure copper anode dissolves into the electrolyte as copper ions, leaving behind impurities as anode mud, while pure copper ions migrate and deposit on the cathode.
How do you decide which ion is discharged at the cathode?
Ions lower down in the electrochemical series are discharged preferentially at the respective electrodes, regardless of concentration, except when there is a very high concentration of a specific ion like chloride.
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