Free Electrochemistry MCQs with Answers
696 Electrochemistry MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Electrochemistry describes electron transfer through oxidation and reduction, identifies oxidizing and reducing agents, and applies oxidation numbers to balance redox equations. It also covers electrode potential and the standard hydrogen electrode, which provides the reference for comparing the reduction tendencies of other electrodes.
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Read the Electrochemistry notesFree MDCAT chapter notes with key terms696 questions · page 8 of 35
- A. Cl
- B. F
- C. Zn
- D. Cu
Explanation: Chlorine (Cl): Chlorine is a halogen and can exhibit a variety of oxidation states, including +3 and +5.
Correct answer: Cl- A. PbSO₄
- B. Pb
- C. SO₂
- D. SO₄
Explanation: In a lead-acid battery, during discharge, the anode (positive electrode) undergoes oxidation.
Correct answer: PbSO₄- A. Loss of electron
- B. Gain of electron
- C. Gain of oxygen
- D. Both a and c
Explanation: Oxidation can be defined in two ways:1. Loss of electron(s): This is the modern definition in terms of election transfer.2.
Correct answer: Both a and c- A. P
- B. O
- C. Cl
- D. Na
Explanation: Phosphorus (P) can exhibit an oxidation state of -3 in compounds like phosphides (P³⁻).
Correct answer: P- A. M
- B. M/10
- C. M/11
- D. M/15
Explanation: In this reaction, Fe goes from +2 to +3 (loss of 1 e⁻) and each of the two S atoms goes from -1 to +6 (loss of 2×7=14 e⁻).
Correct answer: M/15- A. Oxidation occurs at the cathode
- B. Reduction occurs at the anode
- C. Electrons flow from anode to cathode
- D. Cathode is negatively charged
Explanation: In a galvanic cell, oxidation occurs at the anode (negative), and electrons move toward the cathode (positive).
Correct answer: Electrons flow from anode to cathode- A. Zn²⁺ | Zn || Cu | Cu²⁺
- B. Zn | Zn²⁺ || Cu²⁺ | Cu
- C. Zn | Cu²⁺ || Zn²⁺ | Cu
- D. Cu | Cu²⁺ || Zn²⁺ | Zn
Explanation: Anode (oxidation) written first: Zn | Zn²⁺, then cathode: Cu²⁺ | Cu.
Correct answer: Zn | Zn²⁺ || Cu²⁺ | Cu- A. -1.10 V
- B. +1.10 V
- C. +0.42 V
- D. -0.42 V
Explanation: E°cell = E°cathode - E°anode = 0.34 - (-0.76) = +1.10 V.
Correct answer: +1.10 V- A. 0
- B. 1
- C. 2
- D. 4
Explanation: Equivalents of sulfite = Molarity × volume × n-factor = 0.1 × 0.025 × 2 = 0.005. Equivalents of metal salt must also be 0.005.
Correct answer: 2- A. Produce electrons
- B. Maintain electrical neutrality
- C. Speed up reaction
- D. Convert AC to DC
Explanation: Salt bridge provides ions to prevent charge accumulation and maintain neutrality, allowing the cell to keep working.
Correct answer: Maintain electrical neutrality- A. NaCl(aq)
- B. HCl(aq)
- C. Glucose solution
- D. KOH(aq)
Explanation: Glucose does not ionize in solution, thus it is classified as a non-electrolyte.
Correct answer: Glucose solution- A. H₂O is the reducing agent
- B. H₂O is the oxidizing agent
- C. Carbon is the oxidizing agent
- D. Oxidation-reduction does not occur
Explanation: In this reaction, the hydrogen in H₂O goes from a +1 oxidation state to 0 in H₂, meaning it has been reduced.
Correct answer: H₂O is the oxidizing agent- A. CaF₂ + H₂SO₄ → CaSO₄ + 2HF
- B. S + 2H₂SO₄ → 3SO₂ + 2H₂O
- C. Cu + 2H₂SO₄ → CuSO₄ + SO₂ + 2H₂O
- D. PCl₅ + H₂SO₄ → SO₂Cl₂ + POCl₃ + HCl
Explanation: In this reaction, H₂SO₄ oxidizes copper from 0 to +2. It also acts as an acid, though some of the sulfate ions simply act as spectator…
Correct answer: Cu + 2H₂SO₄ → CuSO₄ + SO₂ + 2H₂O- A. Anode
- B. Cathode
- C. Salt bridge
- D. Diaphragm
Explanation: Na⁺ + e⁻ → Na (reduction occurs at the cathode).
Correct answer: Cathode- A. They require external current
- B. They convert chemical energy into electrical energy
- C. Cathode is negative
- D. Anode undergoes reduction
Explanation: Galvanic cells operate spontaneously to produce electricity.
Correct answer: They convert chemical energy into electrical energy- A. Cathode to anode
- B. Anode to cathode
- C. Salt bridge to cathode
- D. Electrolyte to electrodes
Explanation: Electrons always flow from anode → cathode.
Correct answer: Anode to cathode- A. Anode
- B. Cathode
- C. Both electrodes
- D. Electrolyte
Explanation: Electrolysis uses external battery → anode is positive, oxidation happens there.
Correct answer: Anode- A. More with KMnO4
- B. Equal with both oxidizing agents
- C. More with K₂Cr₂O₇
- D. Cannot be determined
Explanation: The oxidizing capacity depends on the number of electrons transferred (the n-factor). For KMnO₄, the n-factor is 5 (Mn⁷⁺ → Mn²⁺).
Correct answer: More with K₂Cr₂O₇- A. Na⁺
- B. H⁺
- C. Cl⁻
- D. OH⁻
Explanation: In aqueous solutions, H⁺ is reduced more easily than Na⁺. So H⁺ → H₂ is produced at cathode.
Correct answer: H⁺- A. Increases in mass
- B. Decreases in mass
- C. Remains unchanged
- D. Dissolves completely
Explanation: Cu²⁺ + 2e⁻ → Cu ( deposited ) so mass of the cathode increases.
Correct answer: Increases in mass