Electrochemistry Important Questions.

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1. Q1Medium

   Which of the following is NOT a characteristic of organic conducting polymers like polyacetylene?

   • A.They exhibit metallic conductivity.
   • B.They are lighter than conventional metals.
   • C.They can be used in flexible electronic devices.
   • D.They are heavier than conventional metals.
   Answer: They are heavier than conventional metals.

   Explanation: Organic conducting polymers like polyacetylene are known for their lightweight nature, metallic conductivity, and flexibility, unlike conventional metals which are denser. This distinction is crucial in applications like lightweight batteries and flexible electronics.

2. Q2Medium

   In a galvanic cell, the reaction Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s) occurs. Which electrode undergoes oxidation?

   • A.Copper electrode
   • B.Zinc electrode
   • C.Anode
   • D.Cathode
   Answer: Zinc electrode

   Explanation: In the given reaction, zinc loses electrons and forms Zn²⁺ ions, indicating that it undergoes oxidation. This is a fundamental concept in redox reactions and electrochemical cells.

3. Q3Medium

   According to Kohlrausch’s Law, the molar conductivity of a strong electrolyte at infinite dilution (Λ°m) is the sum of the contributions of individual ions. Which of the following pairs of ions will have the highest combined contribution?

   • A.Na⁺ and Cl⁻
   • B.K⁺ and Br⁻
   • C.H⁺ and OH⁻
   • D.Ca²⁺ and SO₄²⁻
   Answer: H⁺ and OH⁻

   Explanation: H⁺ and OH⁻ ions have the highest ionic conductivities due to their small size and high mobility in solution, making their combined contribution to molar conductivity the highest among the given options.

4. Q4Medium

   In a fuel cell using hydrogen and oxygen to produce water, the overall reaction is: 2H₂(g) + O₂(g) → 2H₂O(l). What is the role of the electrolyte in this setup?

   • A.Converts chemical energy to electrical energy directly
   • B.Acts as a catalyst for the reaction
   • C.Conducts electrons directly between electrodes
   • D.Conducts ions and prevents electron flow directly between electrodes
   Answer: Conducts ions and prevents electron flow directly between electrodes

   Explanation: In a fuel cell, the electrolyte allows the movement of ions (like OH⁻ in alkaline fuel cells) between the electrodes, facilitating the completion of the circuit while keeping electrons flowing through an external circuit to generate electricity.

5. Q5Medium

   Which of the following is an example of a 2-2 electrolyte?

   • A.NaCl
   • B.KCl
   • C.MgSO₄
   • D.CaCl₂
   Answer: MgSO₄

   Explanation: A 2-2 electrolyte dissociates into two ions each with a +2 or -2 charge, such as Mg²⁺ and SO₄²⁻ in MgSO₄. This classification is based on the charges of the ions produced during dissociation.

6. Q6Medium

   What is the standard electrode potential of the Zn2+/Zn half-cell if the measured emf of the cell Pt(s)|H2(g, 1 bar)|H+(aq, 1M)||Zn2+(aq, 1M)|Zn(s) is -0.76 V?

   • A.A) -0.76 V
   • B.B) +0.34 V
   • C.C) -0.34 V
   • D.D) +0.76 V
   Answer: A) -0.76 V

   Explanation: The emf of the cell involving Zn2+/Zn is directly given as the standard electrode potential for the Zn2+/Zn half-cell, as the SHE (Standard Hydrogen Electrode) has a potential of 0 V. This is a fundamental concept in determining the reduction potential of metals relative to hydrogen.

7. Q7Medium

   Which of the following metals can be oxidized by ferrous ions (Fe2+) under suitable conditions based on standard electrode potentials?

   • A.A) Zinc
   • B.B) Iron
   • C.C) Copper
   • D.D) Magnesium
   Answer: C) Copper

   Explanation: Copper has a higher standard reduction potential than ferrous ions, making it easier to oxidize ferrous ions to ferric ions (Fe3+) while reducing Cu2+ to Cu. This is based on the standard electrode potentials where Cu2+/Cu has a higher potential than Fe3+/Fe2+.

8. Q8Medium

   What is the primary function of a galvanic cell?

   • A.A) Convert electrical energy to chemical energy
   • B.B) Convert chemical energy to electrical energy
   • C.C) Store electrical energy
   • D.D) Produce heat
   Answer: B) Convert chemical energy to electrical energy

   Explanation: A galvanic cell converts the energy released from a spontaneous redox reaction directly into electrical energy, which can be harnessed for various applications like batteries.

9. Q9Medium

   What happens when an external potential of 1.1 V is applied to a galvanic cell?

   • A.A) The reaction continues indefinitely
   • B.B) The cell explodes
   • C.C) The reaction stops and the cell acts as an electrolytic cell
   • D.D) The cell stops conducting electricity
   Answer: C) The reaction stops and the cell acts as an electrolytic cell

   Explanation: When the opposing voltage reaches the cell potential (1.1 V), the redox reaction stops, and further increase in potential reverses the reaction, making the cell function as an electrolytic cell.

10. Q10Medium

    Which of the following is a primary characteristic of a fuel cell?

    • A.A) High thermal pollution
    • B.B) Pollution-free operation
    • C.C) Use of fossil fuels
    • D.D) High maintenance cost
    Answer: B) Pollution-free operation

    Explanation: Fuel cells are known for their pollution-free operation as they directly convert chemical energy from fuels like hydrogen into electricity without producing harmful by-products.

11. Q11Medium

    What is the role of catalysts like platinum in fuel cells?

    • A.A) Decrease the efficiency of the cell
    • B.B) Increase the rate of electrode reactions
    • C.C) Act as electrolytes
    • D.D) Store hydrogen
    Answer: B) Increase the rate of electrode reactions

    Explanation: Catalysts like platinum enhance the rate of the electrode reactions by lowering the activation energy required for the reaction, thus improving the efficiency of the fuel cell.

12. Q12Medium

    Which equation relates Gibbs free energy change (ΔG°) to standard cell potential (E°cell)?

    • A.A) ΔG° = nFE°cell
    • B.B) ΔG° = -nFE°cell
    • C.C) ΔG° = nF/ΔE°cell
    • D.D) ΔG° = -ΔE°cell/F
    Answer: B) ΔG° = -nFE°cell

    Explanation: The relationship between Gibbs free energy change and standard cell potential is given by the equation ΔG° = -nFE°cell, where n is the number of moles of electrons transferred, F is Faraday's constant, and E°cell is the standard cell potential.

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