Introduction
When an electric current passes through a conducting solution or molten compound, it causes chemical changes. These changes are called chemical effects of electric current.
This chapter explains electrolysis, electroplating, and other phenomena related to the chemical effects of current. Understanding these concepts is important for exams, MCQs, and one-word questions.
Electrolysis
Electrolysis is the decomposition of a substance by passing an electric current through it.
- The liquid or molten compound through which current passes is called the electrolyte.
- Two electrodes are used:
- Anode – Positive electrode
- Cathode – Negative electrode
Examples of Electrolytes:
- Copper sulphate solution
- Acidic water
- Sodium chloride solution
Observations in Electrolysis:
- Bubbles of gas may appear at electrodes.
- Metal may get deposited on the cathode.
- The electrolyte may change color.
Electroplating
Electroplating is the process of coating one metal over another using electric current.
Purpose:
- Protect metals from corrosion
- Beautify objects
Process of Electroplating:
- The object to be plated is made the cathode.
- The metal to coat the object is made the anode.
- The electrolyte contains metal ions of the metal to be coated.
- When current passes, metal ions move towards the cathode and deposit there.
Common Electroplating Examples:
- Silver plating of cutlery
- Chrome plating of car parts
Applications of Chemical Effects of Electric Current
- Electroplating – Coating metals like gold, silver, or chromium.
- Purification of metals – Copper purification by electrolysis.
- Production of gases – Hydrogen and oxygen from water electrolysis.
- Manufacturing chemicals – Sodium hydroxide, chlorine, and hydrogen by electrolysis of brine.
Important Terms
- Electrolyte – Conducting liquid
- Electrodes – Conductors used in electrolysis
- Anode – Positive electrode
- Cathode – Negative electrode
- Deposition – Metal collecting on cathode
- Electroplating – Coating metals using electricity
Safety Precautions
- Avoid touching electrodes during electrolysis.
- Use low voltage when performing experiments.
- Handle acids and metal salts carefully.
Summary
- Electric current can produce chemical changes in liquids and solutions.
- Electrolysis decomposes compounds using electricity.
- Electroplating deposits metal on another metal to prevent corrosion or for decoration.
- Knowledge of anode, cathode, and electrolyte is essential for exams.
Important One-Word / Very Short Answers for Exams
- Flow of electric charge – Current
- Device that supplies electric current – Cell
- Path through which current flows – Circuit
- Material that allows current to pass – Conductor
- Material that does not allow current – Insulator
- Liquids that conduct electricity – Electrolytes
- Chemical change caused by current – Electrolysis
- Decomposition of chemicals by electricity – Electrolysis
- Electrodes dipped in liquid – Electrodes
- Positive electrode – Anode
- Negative electrode – Cathode
- Electric current through liquids causes – Chemical reactions
- Formation of bubbles on electrodes – Gas
- Blue-green coating on copper plate – Copper sulphate
- Process of depositing metal using electricity – Electroplating
- Object to be electroplated – Cathode
- Metal plate used for coating – Anode
- Liquid used in electroplating – Electrolyte
- Coating of chromium on objects – Chrome-plating
- Metal commonly used for electroplating – Chromium
- Advantage of electroplating – Protection
- Electroplating prevents – Corrosion
- Chemical effect observed in liquids – Reaction
- Electric tester uses a – Bulb
- Device used to detect weak current – LED
- Bulb glows due to – Heating effect
- Colour change in solution indicates – Chemical effect
- Substance conducting electricity in solution – Ion
- Example of good liquid conductor – Lemon juice
- Example of poor liquid conductor – Distilled water
- Electrode attracting positive ions – Cathode
- Electrode attracting negative ions – Anode
- Electric current causing gas formation – Electrolysis
- Process used to beautify objects – Electroplating
- Use of electroplating in jewellery – Coating