1. Which statement best describes the central idea of electrochemistry?
ⓐ. It deals only with ionic compounds in aqueous solution.
ⓑ. It studies only those reactions that produce heat.
ⓒ. It links redox reactions with energy conversion.
ⓓ. It explains only the colour changes occurring during oxidation.
Correct Answer: It links redox reactions with energy conversion.
Explanation: Electrochemistry is based on redox processes in which electron transfer is linked with energy conversion. In a galvanic cell, chemical energy is converted into electrical energy. In an electrolytic cell, electrical energy is used to bring about chemical change.
2. In terms of electron transfer, oxidation is represented by which change?
ⓐ. Gain of electrons by a species
ⓑ. Loss of electrons by a species
ⓒ. Gain of protons by a species
ⓓ. Loss of neutrons by a species
Correct Answer: Loss of electrons by a species
Explanation: Oxidation is defined as loss of electrons. A species that loses electrons gets oxidized, while the species that gains those electrons gets reduced. This electron-transfer view gives the most general description of redox change.
3. Which statement correctly distinguishes a galvanic cell from an electrolytic cell?
ⓐ. A galvanic cell uses electrical energy to drive a non-spontaneous reaction, whereas an electrolytic cell produces electricity from a spontaneous reaction.
ⓑ. Both galvanic and electrolytic cells convert chemical energy only into heat energy.
ⓒ. A galvanic cell and an electrolytic cell both operate only when the overall reaction is spontaneous.
ⓓ. A galvanic cell produces electricity; an electrolytic cell uses electricity to drive a reaction.
Correct Answer: A galvanic cell produces electricity; an electrolytic cell uses electricity to drive a reaction.
Explanation: The key difference lies in spontaneity and energy conversion. A galvanic cell generates electricity because the redox reaction can occur on its own. An electrolytic cell needs an external source of electrical energy because the redox reaction is not spontaneous.
4. Which process is common to every redox reaction?
ⓐ. Exchange of atoms without change in charge
ⓑ. Transfer of neutrons from one species to another
ⓒ. Transfer of electrons from one species to another
ⓓ. Equalization of concentration on both sides of a membrane
Correct Answer: Transfer of electrons from one species to another
Explanation: A redox reaction always involves electron transfer. One species loses electrons and undergoes oxidation, while another gains electrons and undergoes reduction. Both processes occur simultaneously.
5. A chemical reaction occurring in a cell is found to generate electric current in an external circuit without any external power supply. Which conclusion is correct?
ⓐ. The reaction is non-spontaneous and the cell is electrolytic.
ⓑ. The reaction is spontaneous and the cell is galvanic.
ⓒ. The reaction must involve no change in oxidation number.
ⓓ. The cell can operate only if the reactants are all solids.
Correct Answer: The reaction is spontaneous and the cell is galvanic.
Explanation: When a cell generates current on its own, the redox reaction inside it must be spontaneous. Such a system is a galvanic cell, where chemical energy is converted directly into electrical energy.
6. Which statement about reduction is correct?
ⓐ. Reduction involves gain of electrons.
ⓑ. Reduction involves loss of electrons.
ⓒ. Reduction always means gain of oxygen.
ⓓ. Reduction always means loss of hydrogen.
Correct Answer: Reduction involves gain of electrons.
Explanation: Reduction is the gain of electrons. In a redox process, electrons lost by one species are accepted by another species. That electron gain corresponds to reduction.
7. Which situation represents conversion of electrical energy into chemical energy?
ⓐ. A spontaneous redox reaction producing a current in a cell
ⓑ. Discharge of a galvanic cell connected to a bulb
ⓒ. Use of an external source to force a redox reaction to occur
ⓓ. Electron transfer taking place directly in a combustion flame
Correct Answer: Use of an external source to force a redox reaction to occur
Explanation: When electrical energy is supplied from outside to make a chemical reaction occur, the process is electrolytic. The supplied electrical energy is converted into chemical energy stored in the reaction products.
8. Which statement is correct for any redox process?
ⓐ. Oxidation and reduction occur separately in different reactions.
ⓑ. Oxidation can occur without any accompanying reduction.
ⓒ. Reduction can occur without any electron donor.
ⓓ. They occur simultaneously in a redox process.
Correct Answer: They occur simultaneously in a redox process.
Explanation: Electrons cannot disappear from one species without being accepted by another. Therefore oxidation and reduction are linked processes. The substance losing electrons is oxidized, and the substance gaining them is reduced.
9. Which pair is correctly matched?
ⓐ. Galvanic cell — non-spontaneous reaction driven by external source
ⓑ. Electrolytic cell — spontaneous reaction producing electrical energy
ⓒ. Galvanic cell — chemical energy converted into electrical energy
ⓓ. Electrolytic cell — oxidation absent and only reduction occurs
Correct Answer: Galvanic cell — chemical energy converted into electrical energy
Explanation: A galvanic cell operates through a spontaneous redox reaction and produces electrical energy. An electrolytic cell works in the opposite energy direction, where electrical energy is supplied to carry out a non-spontaneous chemical change. Oxidation and reduction are present in both cases.
10. A redox process is observed only when an external battery is connected to the setup. Which statement is most appropriate?
ⓐ. The setup behaves as an electrolytic cell.
ⓑ. The setup must be a galvanic cell.
ⓒ. The reaction must be spontaneous.
ⓓ. The process cannot involve electron transfer.
Correct Answer: The setup behaves as an electrolytic cell.
Explanation: When a reaction occurs only after supplying electrical energy from an external source, the process is non-spontaneous under ordinary conditions. Such a setup is an electrolytic cell. The external battery forces electron transfer in the required direction.
11. Which statement about an electrochemical cell is correct?
ⓐ. It contains only one half-cell in which both oxidation and reduction occur together.
ⓑ. It contains two half-cells, one for oxidation and one for reduction.
ⓒ. It contains two half-cells, but electrons move through the solution between them.
ⓓ. It contains no separate regions for the two half-reactions.
Correct Answer: It contains two half-cells, one for oxidation and one for reduction.
Explanation: An electrochemical cell is built from two half-cells. Oxidation occurs in one half-cell and reduction occurs in the other. Separating the half-reactions allows electron transfer to occur through an external path, which makes electrical work possible.
12. In an electrochemical cell, electrons move through the external circuit from
ⓐ. the reduction half-cell to the oxidation half-cell
ⓑ. the salt bridge to the cathode
ⓒ. the electrolyte solution to the electrode surface
ⓓ. the oxidation half-cell to the reduction half-cell
Correct Answer: the oxidation half-cell to the reduction half-cell
Explanation: Electrons are released where oxidation occurs. They then travel through the external circuit and are consumed where reduction occurs. So the electron path is always from the oxidation half-cell to the reduction half-cell.
13. Which component mainly maintains ionic continuity between the two half-cells of an electrochemical cell?
ⓐ. The metallic wire connecting the electrodes
ⓑ. The voltmeter connected across the terminals
ⓒ. The electrode surface where electrons are released
ⓓ. The salt bridge or internal ionic connection
Correct Answer: The salt bridge or internal ionic connection
Explanation: Ionic continuity is maintained by ion movement through the salt bridge or any equivalent internal ionic path. The wire carries electrons, not ions. Without ionic continuity, charge would build up in the half-cells and current would stop.
14. What is the main role of the external metallic wire in an electrochemical cell?
ⓐ. It allows cations and anions to migrate between the solutions.
ⓑ. It provides the path for electron flow between half-cells.
ⓒ. It keeps the concentrations of the electrolytes constant.
ⓓ. It prevents oxidation and reduction from taking place together.
Correct Answer: It provides the path for electron flow between half-cells.
Explanation: The metallic wire provides a conducting path for electrons. Electrons released during oxidation travel through this external path and reach the site of reduction. Ion migration is not carried by the wire.
15. If the two half-cells of a working electrochemical cell are connected only by a wire and no internal ionic connection is present, what will happen after a brief moment?
ⓐ. The cell will continue working normally because the wire alone completes the circuit.
ⓑ. The cell will produce a larger current because ions are not disturbed.
ⓒ. The cell will stop because charge balance in the solutions cannot be maintained.
ⓓ. The cell will reverse the direction of electron flow automatically.
Correct Answer: The cell will stop because charge balance in the solutions cannot be maintained.
Explanation: Electron flow through the wire causes charge to accumulate in the half-cells unless ions can move internally to preserve electrical neutrality. Without ionic continuity, one solution becomes increasingly positive and the other increasingly negative. This opposes further electron flow, so the cell stops.
16. Which statement best explains why oxidation and reduction are separated into two half-cells in an electrochemical cell?
ⓐ. It makes electron flow through an external circuit usable.
ⓑ. Separation increases the mass of reactants in both half-cells.
ⓒ. Separation prevents any ion movement in the system.
ⓓ. Separation removes the need for overall charge balance.
Correct Answer: It makes electron flow through an external circuit usable.
Explanation: If oxidation and reduction occur in separate half-cells, electrons released in one place must travel through an external path to reach the other. That directed electron flow can be used as electric current. If both processes occurred directly in the same region, the energy would not be harnessed in this way.
17. Which condition must be satisfied for a galvanic cell to operate on its own?
ⓐ. The overall redox reaction must be spontaneous.
ⓑ. The reactants must be present only in molten state.
ⓒ. The two electrodes must always be made of the same metal.
ⓓ. The cell must be connected to an external battery.
Correct Answer: The overall redox reaction must be spontaneous.
Explanation: A galvanic cell generates electrical energy without outside assistance. That is possible only when the redox reaction proceeds spontaneously. If the reaction is non-spontaneous, external electrical energy is required instead.
18. In a galvanic cell, the main energy conversion is
ⓐ. heat energy into light energy
ⓑ. electrical energy into chemical energy
ⓒ. chemical energy into electrical energy
ⓓ. mechanical energy into electrical energy
Correct Answer: chemical energy into electrical energy
Explanation: A galvanic cell uses a spontaneous redox reaction as the source of energy. The chemical energy released during the reaction is converted into electrical energy, which appears as current in the external circuit.
19. Which statement about charge transport in a galvanic cell is correct?
ⓐ. Electrons move through the salt bridge, while ions move through the wire.
ⓑ. Both electrons and ions move only through the electrolyte solutions.
ⓒ. Electrons use the external wire, while ions use the internal path.
ⓓ. Both electrons and ions move only through the metallic conductor.
Correct Answer: Electrons use the external wire, while ions use the internal path.
Explanation: The metallic wire provides the path for electrons. The internal ionic connection, usually a salt bridge, allows ions to migrate and maintain charge balance. Both paths are needed for continuous operation of the cell.
20. A redox reaction is carried out in such a way that oxidation and reduction occur in separate compartments connected by a wire and an internal ionic path. What is the main advantage of this arrangement?
ⓐ. It prevents any electron transfer from occurring.
ⓑ. It allows the chemical change to proceed without oxidation.
ⓒ. It converts all chemical energy directly into heat.
ⓓ. It makes external electron flow usable as electric current.
Correct Answer: It makes external electron flow usable as electric current.
Explanation: When the two half-reactions are separated, electrons cannot pass directly from one reactant to another. They must travel through the external circuit, and that directed electron flow is obtained as electric current.
