Day 31 – Morning Session: Chemistry – Electrochemical Cells & Batteries – ECET 2026

Electrochemistry is a very important chapter in ECET 2026 Chemistry. Every year, 1–2 direct questions are asked from Electrochemical Cells and Batteries. By mastering this topic, students can score easy marks in Chemistry.

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⚙️ Concept Notes – Electrochemical Cells

🔋 Electrochemical Cell

• A device that converts chemical energy into electrical energy.
• Works on redox reaction principle (oxidation at anode, reduction at cathode).
• Consists of two half-cells connected by a salt bridge.

👉 Example: Daniell Cell

• Zn rod dipped in ZnSO₄ solution (anode)
• Cu rod dipped in CuSO₄ solution (cathode)
• Salt bridge allows ion transfer, maintaining neutrality.

Reactions:
At Anode:

At Cathode:

⚡ Electrode Potential

• Electrode Potential (E): Tendency of an electrode to lose or gain electrons.
• Standard Electrode Potential (E°): Measured under 1M, 1 atm, 25°C conditions.

👉 Formula (Cell Potential):

👉 Nernst Equation:

Batteries

1. Primary Cells (Non-rechargeable):
   • Once used, cannot be recharged.
   • Example: Dry Cell, Mercury Cell.
2. Secondary Cells (Rechargeable):
   • Can be recharged and reused.
   • Examples: Lead-acid battery, Nickel-Cadmium battery, Lithium-ion battery.

👉 Example – Lead-acid battery (car battery):

• Electrodes: Lead (Pb) and Lead dioxide (PbO₂).
• Electrolyte: Sulphuric acid (H₂SO₄).
• Voltage per cell ≈ 2V (12V battery = 6 cells in series).

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🔟 10 Expected MCQs – ECET 2026

Q1. An electrochemical cell converts:
A) Electrical energy → Chemical energy
B) Chemical energy → Electrical energy
C) Heat energy → Chemical energy
D) None

Q2. Oxidation occurs at:
A) Cathode
B) Anode
C) Both
D) None

Q3. Daniell cell uses:
A) Zn & Cu
B) Pb & H₂
C) Ni & Cd
D) Fe & HCl

Q4. The standard hydrogen electrode potential is taken as:
A) +1.0 V
B) 0.0 V
C) –1.0 V
D) 2.0 V

Q5. Formula for cell potential is:
A) E = E° – RT/nF lnQ
B) E = E(cathode) – E(anode)
C) Both A & B
D) None

Q6. Lead-acid battery is:
A) Primary cell
B) Secondary cell
C) Fuel cell
D) Dry cell

Q7. Dry cell is:
A) Primary cell
B) Secondary cell
C) Fuel cell
D) Storage battery

Q8. In a Daniell cell, cathode is:
A) Zinc rod
B) Copper rod
C) Salt bridge
D) None

Q9. Which battery is used in vehicles?
A) Dry cell
B) Mercury cell
C) Lead-acid battery
D) Lithium-ion battery

Q10. Which of the following is rechargeable?
A) Mercury cell
B) Lead-acid battery
C) Dry cell
D) All

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✅ Answer Key

Q.No	Answer
Q1	B
Q2	B
Q3	A
Q4	B
Q5	C
Q6	B
Q7	A
Q8	B
Q9	C
Q10	B

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🧠 Explanations

• Q1 → B: Electrochemical cell converts chemical energy → electrical energy.
• Q2 → B: Oxidation always at anode, reduction at cathode.
• Q3 → A: Daniell cell = Zn (anode), Cu (cathode).
• Q4 → B: Standard hydrogen electrode = 0.0 V.
• Q5 → C: Both Nernst equation & E(cell) = E(cathode) – E(anode).
• Q6 → B: Lead-acid battery = secondary (rechargeable).
• Q7 → A: Dry cell is a primary cell.
• Q8 → B: In Daniell cell, cathode = copper rod.
• Q9 → C: Lead-acid battery is used in automobiles.
• Q10 → B: Lead-acid battery is rechargeable.

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🎯 Why This Practice Matters for ECET 2026

Electrochemical Cells & Batteries questions are formula-based and repeated every year. By preparing electrode potentials, Nernst equation, and types of batteries, you can secure easy Chemistry marks.

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