Free Redox Reactions MCQs with Answers
102 Redox Reactions MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Redox reactions involve oxidation and reduction occurring together, with electrons transferred between species or oxidation numbers changing. The topic covers assigning oxidation states, identifying oxidizing and reducing agents, balancing redox equations by oxidation number or half-reaction methods, and connecting chemical changes with galvanic and electrolytic cells.
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102 questions · page 3 of 6
- A. secondary cell
- B. primary cell
- C. voltaic cell
- D. both A & C
Explanation: A lead accumulator is a secondary cell because its discharge reaction can be reversed by passing an external current.
Correct answer: both A & C- A. periodic table
- B. groups
- C. periods
- D. electrochemical series
Explanation: The electrochemical series arranges elements or ions according to their standard electrode potentials, measured relative to the standard…
Correct answer: electrochemical series- A. by addition of fresh solution
- B. by replacing external circuit with external source of electricity
- C. by removal of solution
- D. by heating it
Explanation: A rechargeable voltaic cell is restored by forcing the reverse redox reaction with an external source of electrical energy.
Correct answer: by replacing external circuit with external source of electricity- A. external electric circuit
- B. salt bridge
- C. movement of ions
- D. all of the above
Explanation: In a galvanic cell, oxidation at the anode releases electrons and reduction at the cathode consumes them, so electrons travel through the…
Correct answer: external electric circuit- A. spontaneous reaction
- B. non-wpontaneous reaction
- C. neutralization
- D. all of above
Explanation: An electrolytic cell uses an external electrical supply to drive a non-spontaneous redox reaction.
Correct answer: non-wpontaneous reaction- A. neutralization
- B. oxidation
- C. reduction
- D. both B & C
Explanation: A voltaic cell produces electricity through a coupled redox process: oxidation occurs at the anode and reduction occurs at the cathode.
Correct answer: both B & C- A. Free electrons
- B. Free molecules
- C. Free ions
- D. Atoms of Na and Cl
Explanation: Molten NaCl contains mobile Na+ and Cl- ions, which migrate to opposite electrodes and carry charge through the liquid.
Correct answer: Free ions- A. Chemical energy is converted into electricity
- B. Chemical energy is converted into heat
- C. Electrical energy is converted into chemical energy
- D. Electrical energy is converted into heat
Explanation: A galvanic cell converts the chemical energy released by a spontaneous redox reaction into electrical energy.
Correct answer: Chemical energy is converted into electricity- A. From cathode to anode in outer circuit
- B. From anode to cathode outside the cell
- C. From cathode to anode inside the cell
- D. both B & C
Explanation: In the external circuit of an electrolytic cell, conventional current flows from the positive anode toward the negative cathode, opposite…
Correct answer: From anode to cathode outside the cell- A. H2 is deposited at cathode
- B. Colour of the solution becomes fade
- C. Cu is deposited at anode
- D. All are possible
Explanation: At the cathode, Cu2+ is preferentially reduced to Cu, while at the platinum anode water is oxidised to oxygen; Cu2+ is therefore removed…
Correct answer: Colour of the solution becomes fade- A. Displacement
- B. Reduction
- C. Disproportionation reaction
- D. Double displacement reaction
Explanation: Hot concentrated caustic soda reacts with chlorine as 3Cl2 + 6NaOH -> 5NaCl + NaClO3 + 3H2O.
Correct answer: Disproportionation reaction- A. Reduction occurs at anode
- B. K+ ion transfer from salt bridge to left beaker of ZnSO4
- C. Oxidation occurs at cathode
- D. Anode is negatively charged
Explanation: In a Zn-Cu galvanic cell, zinc is oxidised at the anode: Zn -> Zn2+ + 2e-.
Correct answer: Anode is negatively charged- A. H2SO4
- B. KMnO4
- C. H2S
- D. K2CrO4
Explanation: H2SO4, KMnO4 and K2CrO4 all contain oxygen and are oxy compounds or oxy salts, whereas H2S is a binary hydride containing no oxygen.
Correct answer: H2S- A. Silver oxide battery
- B. Fuel cell
- C. Nickel cadmium cell
- D. Lead accumulator
Explanation: Nickel-cadmium cells are rechargeable secondary cells that were commonly used in portable electronic devices, including older laptops.
Correct answer: Nickel cadmium cell- A. A
- B. Ag
- C. Both
- D. Neither
Explanation: In an Al-Ag galvanic cell, aluminium is more readily oxidised and acts as the anode, while Ag+ ions are reduced at the silver cathode.
Correct answer: Ag- A. Ni2+ + Zn -> Zn2+ + Ni
- B. Zn2+ + Ni -> Ni2+ + Zn
- C. Zn2+ + Ni2+ -> Zn + Ni
- D. Zn + Ni -> Zn2+ + Ni2+
Explanation: In the given cell, Zn is oxidized to Zn2+ ions, and Ni2+ ions are reduced to Ni atoms. The anode is Zn, and the cathode is Ni.
Correct answer: Ni2+ + Zn -> Zn2+ + Ni- A. Sulfur gas
- B. Sulfur dioxide
- C. Sulfur trioxide
- D. Hydrogen sulfide
Explanation: When elemental sulfur is burnt, it reacts with oxygen in the air to form sulfur dioxide gas (SO2), as shown by the following equation: S +…
Correct answer: Sulfur trioxide- A. Yellow to blue
- B. Orange to yellow
- C. Yellow to orange
- D. Green to yellow
Explanation: Potassium dichromate is a powerful oxidizing agent, and its color changes depending on its oxidation state.
Correct answer: Orange to yellow- A. O2, H2
- B. O2, Na
- C. O2, SO2
- D. O2, S2O4-2
Explanation: Keeping in mind the electrochemical series; OH- gets discharged at the anode whereas H+ gets discharged at the cathode giving out O2 and…
Correct answer: O2, H2- A. Fe
- B. Cu
- C. Zn
- D. Sn
Explanation: d) Sn (tin):The action of nitric acid (HNO3) on tin (Sn) does indeed produce nitric oxide (NO).
Correct answer: Sn