Try each question on your own first. Use the Show Answer button only after you have selected your option, then read the explanation and revise the related concept from your chapter notes.
Explanation: Molar conductivity (Λm) is conductivity divided by molar concentration, giving units of S m² mol⁻¹.
2. Kohlrausch's law of independent migration of ions is used to determine:
A. The limiting molar conductivity of weak electrolytes
B. The pH of a solution
C. The standard reduction potential
D. The rate constant of a reaction
Answer: A. The limiting molar conductivity of weak electrolytes
Explanation: Since weak electrolytes cannot be extrapolated directly, Kohlrausch's law allows their limiting molar conductivity to be calculated by summing ionic contributions.
3. In a galvanic cell, oxidation takes place at the:
A. Anode
B. Cathode
C. Salt bridge
D. Both electrodes equally
Answer: A. Anode
Explanation: By convention, oxidation (loss of electrons) always occurs at the anode in any electrochemical cell.
4. The standard reduction potential of the standard hydrogen electrode (SHE) is taken as:
A. 0.00 V
B. 1.00 V
C. -1.00 V
D. 0.76 V
Answer: A. 0.00 V
Explanation: The SHE is the reference electrode and is arbitrarily assigned a potential of exactly 0.00 V.
5. Which equation correctly relates Gibbs free energy change and the EMF of a cell?
A. ΔG = -nFE
B. ΔG = nFE
C. ΔG = -nF/E
D. ΔG = FE/n
Answer: A. ΔG = -nFE
Explanation: The relation ΔG = -nFE connects the free energy change to the number of electrons transferred (n), Faraday's constant (F), and cell EMF (E).
6. Faraday's first law of electrolysis states that the mass of substance deposited is proportional to:
A. The quantity of charge passed
B. Current alone
C. Time alone
D. Resistance of the cell
Answer: A. The quantity of charge passed
Explanation: Mass deposited (w) = ZQ, where Q is the total charge passed and Z is the electrochemical equivalent.
7. The specific conductance (κ) of an electrolytic solution generally ___ on dilution.
A. Decreases
B. Increases
C. Remains constant
D. First increases then decreases
Answer: A. Decreases
Explanation: Dilution reduces the number of ions per unit volume, lowering the specific conductance even though molar conductivity increases.
8. A hydrogen-oxygen fuel cell produces which by-product?
A. Water
B. Carbon dioxide
C. Methane
D. Ammonia
Answer: A. Water
Explanation: In an H2-O2 fuel cell, hydrogen is oxidized at the anode and oxygen is reduced at the cathode, combining to form water.
9. Corrosion of iron (rusting) is essentially:
A. An electrochemical process
B. A purely physical process
C. A nuclear process
D. A photochemical process
Answer: A. An electrochemical process
Explanation: Rusting involves oxidation of iron at anodic spots and reduction of oxygen at cathodic spots on the metal surface, forming a tiny galvanic cell.
10. The Nernst equation relates the electrode potential of a cell mainly to:
A. The concentration of the reacting species
B. Temperature alone
C. Pressure alone
D. Time
Answer: A. The concentration of the reacting species
Explanation: The Nernst equation, E = E° - (RT/nF) ln Q, shows how electrode potential varies with ion concentrations (reaction quotient Q).
11. Which of the following is an example of a secondary (rechargeable) cell?
A. Lead storage battery
B. Dry cell
C. Mercury cell
D. Leclanché cell
Answer: A. Lead storage battery
Explanation: A lead storage battery can be recharged by passing current in the reverse direction, unlike primary cells such as the dry cell.
12. The number of electrons required to reduce 1 mole of Al³⁺ to Al metal is:
A. 3
B. 1
C. 2
D. 4
Answer: A. 3
Explanation: Al³⁺ + 3e⁻ → Al requires three electrons per aluminium ion reduced.
