Electrolysis Practice Questions
WAEC (West Africa) · WAEC Chemistry · 145 free MCQs with instant results and detailed explanations.
145
Total
45
Easy
74
Medium
26
Hard
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Sample Questions from Electrolysis
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Q1
Easy
What is the primary purpose of electrolysis in chemistry?
A.
To separate elements from compounds
B.
To combine elements into compounds
C.
To produce heat energy
D.
To measure electrical resistance
Show Answer & Explanation
Correct Answer: A
Electrolysis is primarily used to separate elements from their compounds by passing an electric current through the compound, causing it to dissociate into its constituent elements.
Q2
Easy
In the electrolysis of molten sodium chloride (NaCl), what is produced at the cathode?
A.
Chlorine gas
B.
Sodium metal
C.
Sodium ions
D.
Hydrogen gas
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Correct Answer: B
During electrolysis of molten sodium chloride, sodium ions migrate to the cathode where they gain electrons to form sodium metal, making it the product at the cathode.
Q3
Easy
What happens to the concentration of ions in an electrolyte during electrolysis?
A.
It increases indefinitely
B.
It decreases over time
C.
It remains constant
D.
It fluctuates randomly
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Correct Answer: B
During electrolysis, ions are either discharged at the electrodes or consumed in the reactions, leading to a decrease in their concentration over time in the electrolyte solution.
Q4
Medium
What is the primary purpose of electrolysis in industrial applications?
A.
To separate elements from compounds
B.
To increase the temperature of a solution
C.
To ionize gases in the atmosphere
D.
To facilitate combustion reactions
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Correct Answer: A
Electrolysis is primarily used to separate elements from their compounds, making it essential in processes like the extraction of metals from ores.
Q5
Medium
During the electrolysis of copper(II) sulfate solution using inert electrodes, which substance is deposited at the cathode?
A.
Copper
B.
Sulfur
C.
Oxygen
D.
Hydrogen
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Correct Answer: A
In the electrolysis of copper(II) sulfate, copper ions migrate to the cathode where they gain electrons and are deposited as solid copper.
Q6
Medium
In electrolysis, what is the role of the anode?
A.
To supply electrons
B.
To attract cations
C.
To reduce anions
D.
To decompose water
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Correct Answer: B
The anode attracts cations from the electrolyte, facilitating oxidation reactions as cations lose electrons at the anode during electrolysis.
Q7
Medium
What happens to the pH of the solution during the electrolysis of water?
A.
It decreases at the anode and increases at the cathode
B.
It remains constant throughout
C.
It increases at the anode and decreases at the cathode
D.
It decreases at both electrodes
Show Answer & Explanation
Correct Answer: A
During the electrolysis of water, hydroxide ions are produced at the cathode, increasing pH, while protons are released at the anode, decreasing pH.
Q8
Hard
When 2.5 moles of NaCl are electrolyzed in molten state, how many moles of sodium can be produced at the cathode?
A.
2.5 moles
B.
5.0 moles
C.
1.25 moles
D.
0.25 moles
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Correct Answer: A
In the electrolysis of NaCl, 1 mole of NaCl produces 1 mole of sodium. Thus, 2.5 moles of NaCl will produce 2.5 moles of sodium.
Q9
Hard
During the electrolysis of copper(II) sulfate solution using inert electrodes, what is the primary product at the anode?
A.
Copper
B.
Oxygen
C.
Hydrogen
D.
Sulfur dioxide
Show Answer & Explanation
Correct Answer: B
At the anode, water is oxidized to produce oxygen gas in the electrolysis of copper(II) sulfate solution with inert electrodes. Copper is deposited at the cathode instead.
Q10
Hard
In the electrolysis of dilute sulfuric acid using platinum electrodes, which of the following reactions occurs at the anode?
A.
2H2O ā O2 + 4H+ + 4eā
B.
2H+ + 2eā ā H2
C.
SO4^2ā + 2eā ā SO2 + O2
D.
H2SO4 ā H2 + SO4^2ā + 2eā
Show Answer & Explanation
Correct Answer: A
At the anode, water is oxidized to produce oxygen gas, protons, and electrons. This demonstrates the process of oxidation occurring in electrolysis.
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Electrolysis ā WAEC (West Africa) WAEC Chemistry Practice Questions Online
This page contains 145 practice MCQs for the chapter Electrolysis in WAEC (West Africa) WAEC Chemistry. The questions are organized by difficulty ā 45 easy, 74 medium, 26 hard ā so you can choose the right level for your preparation.
Every question includes a detailed explanation to help you understand the concept, not just memorize answers. Take a timed quiz to simulate exam conditions, or practice at your own pace with no time limit.