Chemical Effects of Electric Current Part 1: MCQs (Q1–Q25)
⚡ Chemical Effects of Electric Current – MCQs for Class 8 Science
Part 1: Q1–Q25
Q1. Which solution is commonly used in laboratories to test chemical effects of current?
A) Distilled water
B) Lemon juice
C) Salt solution
D) Sugar solution
✅ Correct Answer: C) Salt solution
Explanation:
- A) Distilled water is a poor conductor.
- B, D) Lemon juice & sugar solution can conduct, but not widely used in labs.
- C) ✔ Salt solution conducts electricity well and is used for experiments.
Q2. The passage of current through a conducting solution causes:
A) Heat effect only
B) Magnetic effect only
C) Chemical effect
D) No effect
✅ Correct Answer: C) Chemical effect
Explanation:
- A, B) Heat and magnetic effects occur in solids, not in liquids.
- C) ✔ Electrolysis takes place, causing chemical changes.
- D) Wrong – there is a visible effect.
Q3. The process of depositing a layer of metal on another material by electricity is called:
A) Galvanization
B) Electroplating
C) Corrosion
D) Insulation
✅ Correct Answer: B) Electroplating
Explanation:
- A) Galvanization = zinc coating by dipping, not current.
- B) ✔ Electroplating = coating via electrolysis.
- C) Corrosion = rusting/tarnishing.
- D) Insulation = non-conductive covering.
Q4. The effect of current due to passage through copper sulphate solution is shown by:
A) Heating
B) Electroplating
C) Magnetization
D) Combustion
✅ Correct Answer: B) Electroplating
Explanation:
- B) ✔ Electrolysis of CuSO₄ deposits copper on electrode.
Q5. Which gas is released at cathode during electrolysis of water?
A) Oxygen
B) Hydrogen
C) Nitrogen
D) Carbon dioxide
✅ Correct Answer: B) Hydrogen
Explanation:
- B) ✔ Water → H₂ at cathode, O₂ at anode.
Q6. Which instrument is used to test conductivity of liquids?
A) Hydrometer
B) Voltmeter
C) Conductivity tester
D) Ammeter
✅ Correct Answer: C) Conductivity tester
Explanation:
- C) ✔ Tester with LED/bulb shows current flow in solution.
Q7. Pure/distilled water is a:
A) Good conductor
B) Poor conductor
C) Superconductor
D) Semiconductor
✅ Correct Answer: B) Poor conductor
Explanation:
- B) ✔ Pure water lacks free ions → poor conductor.
Q8. Which of these increases conductivity of distilled water?
A) Adding sugar
B) Adding common salt
C) Adding oil
D) Adding kerosene
✅ Correct Answer: B) Adding common salt
Explanation:
- B) ✔ Salt ionizes, increasing conductivity.
Q9. The chemical effect of current is used in:
A) Electroplating
B) Electrolysis
C) Purification of metals
D) All of these
✅ Correct Answer: D) All of these
Explanation:
- D) ✔ All are practical uses of chemical effects.
Q10. Which electrode is connected to positive terminal in electroplating?
A) Cathode
B) Anode
C) Both
D) None
✅ Correct Answer: B) Anode
Explanation:
- B) ✔ Anode is positive electrode (metal to be plated dissolves).
Q11. The cathode is connected to:
A) Positive terminal
B) Negative terminal
C) Both
D) None
✅ Correct Answer: B) Negative terminal
Explanation:
- B) ✔ Cathode is negative electrode, where deposition happens.
Q12. Electroplating improves:
A) Appearance only
B) Resistance to corrosion only
C) Both appearance and corrosion resistance
D) Weight of metal
✅ Correct Answer: C) Both appearance and corrosion resistance
Explanation:
- C) ✔ Electroplating gives shine & prevents corrosion.
Q13. Which metal is commonly used for electroplating to prevent corrosion?
A) Copper
B) Zinc
C) Chromium
D) Lead
✅ Correct Answer: C) Chromium
Explanation:
- C) ✔ Chromium plating resists corrosion & gives shine.
Q14. During electrolysis of copper sulphate, copper is deposited on:
A) Anode
B) Cathode
C) Both electrodes
D) None
✅ Correct Answer: B) Cathode
Explanation:
- B) ✔ Positive Cu²⁺ ions move to cathode (negative electrode).
Q15. Which one of these liquids is a good conductor?
A) Kerosene
B) Petrol
C) Lemon juice
D) Distilled water
✅ Correct Answer: C) Lemon juice
Explanation:
- C) ✔ Contains acids (ions) → good conductor.
Q16. In electroplating of copper on iron, the iron article is connected to:
A) Anode
B) Cathode
C) Both
D) None
✅ Correct Answer: B) Cathode
Explanation:
- B) ✔ Object to be plated is always cathode.
Q17. The process of breaking up of a compound solution by electricity is:
A) Galvanization
B) Oxidation
C) Electrolysis
D) Sublimation
✅ Correct Answer: C) Electrolysis
Explanation:
- C) ✔ Electrolysis = decomposition by electric current.
Q18. Which solution will not conduct electricity?
A) Salt solution
B) Acid solution
C) Sugar solution
D) Base solution
✅ Correct Answer: C) Sugar solution
Explanation:
- C) ✔ Sugar doesn’t ionize, hence no conductivity.
Q19. The metal used in electroplating expensive jewelry is:
A) Iron
B) Nickel
C) Silver/Gold
D) Zinc
✅ Correct Answer: C) Silver/Gold
Explanation:
- C) ✔ Used to give ornaments shiny and costly finish.
Q20. During electrolysis of water, oxygen is released at:
A) Cathode
B) Anode
C) Both electrodes
D) None
✅ Correct Answer: B) Anode
Explanation:
- B) ✔ O₂ released at positive terminal (anode).
Q21. Which one is a conductor of electricity?
A) Tap water
B) Distilled water
C) Sugar solution
D) Oil
✅ Correct Answer: A) Tap water
Explanation:
- A) ✔ Tap water contains dissolved salts & minerals → conducts current.
Q22. Which of the following solutions will glow a bulb when electricity is passed?
A) Distilled water
B) Sugar solution
C) Lemon juice
D) Alcohol
✅ Correct Answer: C) Lemon juice
Explanation:
- C) ✔ Acids release ions → conduct current → bulb glows.
Q23. An electrolyte is:
A) Substance conducting electricity in solid state
B) Liquid that decomposes on passing current
C) Metal wire conducting electricity
D) None
✅ Correct Answer: B) Liquid that decomposes on passing current
Explanation:
- B) ✔ Electrolytes like salt solution decompose → ions move.
Q24. Electroplating is used in:
A) Utensils
B) Ornaments
C) Car parts
D) All of these
✅ Correct Answer: D) All of these
Explanation:
- D) ✔ Widely used to protect & beautify articles.
Q25. Which statement about electroplating is INCORRECT?
A) It is based on electrolysis
B) It protects against corrosion
C) It always makes object heavier
D) It improves appearance
✅ Correct Answer: C) It always makes object heavier
Explanation:
- C) ✔ Deposition may not significantly change weight, but improves shine & resistance.
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