IGCSE Coordinated Science Virtual Lab

Electrolysis of Dilute Sulfuric Acid

ALIGNED WITH IGCSE SYLLABUS

Electrolysis Apparatus

DC POWER
ANODE (+)
CATHODE (-)
OXYGEN
HYDROGEN

Observations

• Electrolysis is not active. Turn on the power to begin.
• No gases are being produced yet.
• The solution remains unchanged.

Gas Testing

Collect gases and test their properties using standard IGCSE tests:

No test performed yet. Collect gases first, then click a test button.

Control Panel

Electrolysis Information

Electrolysis of dilute sulfuric acid decomposes water into hydrogen and oxygen gases:

Overall Reaction: 2H₂O(l) → 2H₂(g) + O₂(g)
At Cathode (-): 4H⁺(aq) + 4e⁻ → 2H₂(g) [Reduction]
At Anode (+): 2H₂O(l) → O₂(g) + 4H⁺(aq) + 4e⁻ [Oxidation]
IGCSE Tip: Remember that the volume ratio of hydrogen to oxygen is 2:1. This is because water (H₂O) has two hydrogen atoms for every oxygen atom.

Sulfuric acid provides H⁺ and SO₄²⁻ ions that conduct electricity, but only water is electrolyzed.

IGCSE Assessment (Total: 25 marks)

Answer the following questions based on your observations from the experiment and your IGCSE knowledge.

1. Which gas is produced at the cathode during electrolysis of dilute sulfuric acid? (1 mark)

a) Oxygen
b) Hydrogen
c) Sulfur dioxide
d) Chlorine

2. What is the volume ratio of hydrogen to oxygen gas produced? (1 mark)

a) 1:1
b) 1:2
c) 2:1
d) 1:8

3. What happens when a glowing splint is introduced to oxygen gas? (1 mark)

a) It goes out with a pop sound
b) It reignites
c) It burns with a blue flame
d) It produces soot

4. What is the purpose of adding sulfuric acid to water in this experiment? (1 mark)

a) To produce more gas
b) To increase the boiling point
c) To provide ions for conduction
d) To change the color of the solution

5. Which electrode is connected to the positive terminal of the battery? (1 mark)

a) Cathode
b) Anode
c) Both electrodes
d) Neither electrode

6. What type of ions move toward the cathode during electrolysis? (1 mark)

a) Anions
b) Cations
c) Both anions and cations
d) Neutral atoms

7. During electrolysis of dilute sulfuric acid, what happens to the concentration of the acid? (1 mark)

a) It increases
b) It decreases
c) It remains constant
d) It becomes zero

8. What is the product at the anode when concentrated sulfuric acid is electrolyzed? (1 mark)

a) Hydrogen
b) Oxygen
c) Sulfur dioxide
d) Water vapor

9. Which gas burns with a 'pop' sound? (1 mark)

a) Oxygen
b) Hydrogen
c) Carbon dioxide
d) Nitrogen

10. What type of reaction occurs at the cathode? (1 mark)

a) Oxidation
b) Reduction
c) Neutralization
d) Decomposition

11. Why is DC current used instead of AC current in electrolysis? (1 mark)

a) AC is more expensive
b) DC provides constant polarity
c) AC causes heating
d) DC is safer

12. What would happen if platinum electrodes were replaced with copper electrodes? (1 mark)

a) No change
b) Copper would dissolve at anode
c) More gas would be produced
d) Electrolysis would stop

13. Which ion is responsible for conduction in the electrolyte? (1 mark)

a) SO₄²⁻ only
b) H⁺ only
c) OH⁻ only
d) Both H⁺ and SO₄²⁻

14. What is the oxidation state of sulfur in H₂SO₄? (1 mark)

a) +2
b) +4
c) +6
d) -2

15. How does increasing the voltage affect the rate of electrolysis? (1 mark)

a) Decreases the rate
b) No effect
c) Increases the rate
d) Stops the process

16. Write the half-reaction that occurs at the anode during electrolysis of dilute sulfuric acid. (2 marks)

17. Explain why the volume of hydrogen gas collected is twice that of oxygen gas. (2 marks)

18. Describe how you would test for hydrogen gas and what positive result you would observe. (2 marks)

19. What safety precautions should be taken when performing this experiment? (2 marks)

20. Explain the role of sulfuric acid in the electrolysis of water. Why is it not consumed in the reaction? (3 marks)

Assessment Results

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