Electrochemical cells are an important part of Electrochemistry and an important area to study for the UP TGT Science Exam

Two important examples are the Leclanché cell and the lead storage battery. Understanding their components, electrodes, electrolytes, EMF and working can help you solve both direct and conceptual questions.

Let's understand these two cells in detail.

What Is a Leclanché Cell?

The Leclanché cell is a type of primary electrochemical cell.

Its important components include:

• Electrolyte: NH₄Cl
• Anode: Zinc (Zn)
• Depolarizer: MnO₂
• Approximate EMF: 1.5 V

These are important facts for exam preparation because questions can directly ask about the electrolyte, electrode, function of MnO₂ or EMF of the cell.

What Is the Role of MnO₂ in a Leclanché Cell?

MnO₂ acts as a depolarizer in the Leclanché cell.

Therefore, remember:

Leclanché Cell → MnO₂ → Depolarizer

What Is the EMF of a Leclanché Cell?

The approximate EMF of a Leclanché cell is:

1.5 V

This is an important fact that can appear as a direct MCQ.

What Is a Lead Storage Battery?

A lead storage battery is a secondary cell, which means it can be recharged.

Its important components are:

• Positive electrode: PbO₂
• Negative electrode: Pb
• Electrolyte: H₂SO₄
• Approximate EMF: 2.0 V per cell

Unlike a primary cell, a lead storage battery can be recharged by supplying electrical energy.

Why Is a Lead Storage Battery Called a Secondary Cell?

A lead storage battery is called a secondary cell because its electrochemical reactions can be reversed during charging.

During discharge, the battery produces electrical energy. During charging, electrical energy is supplied to restore the active materials.

Therefore:

Leclanché Cell → Primary Cell

Lead Storage Battery → Secondary Cell

What Happens During Discharge of a Lead Storage Battery?

During discharge, the lead storage battery supplies electrical energy to an external circuit.

An important change during discharge is the formation of PbSO₄ at both electrodes. The practice material provided for this topic specifically tests the formation of PbSO₄ during discharge.

At the negative electrode, the reaction can be represented as:

Pb + SO₄²⁻ → PbSO₄ + 2e⁻

At the positive electrode, PbO₂ also undergoes a reaction resulting in the formation of PbSO₄.

The key point to remember is:

During discharge → PbSO₄ is formed at both electrodes.

What Happens to H₂SO₄ During Discharge?

The concentration of H₂SO₄ decreases during discharge.

This is an important conceptual point for UP PGT Chemistry preparation and is directly tested in the supplied practice material.

Remember:

Discharge of lead storage battery → H₂SO₄ concentration decreases

What Happens During Charging?

A lead storage battery can be recharged by supplying electrical energy.

During charging, the discharge process is reversed and the active materials are restored.

In simple terms:

Discharge → Chemical energy → Electrical energy

Charging → Electrical energy → Chemical energy

Understanding this difference is important when answering questions about primary and secondary cells.

EMF of a Lead Storage Cell

The approximate EMF of one lead storage cell is:

2.0 V

This value is important for direct questions as well as numerical applications.

For example, if six lead storage cells are connected in series:

6 × 2 V = 12 V

Therefore:

Six cells in series → Approximately 12 V

The supplied practice material includes this type of question.

Leclanché Cell vs Lead Storage Battery

This comparison can help you quickly revise the most important differences between the two cells.

Important Points for UP PGT Chemistry

Leclanché Cell

• Primary cell
• NH₄Cl is the electrolyte
• Zn acts as the anode
• MnO₂ acts as the depolarizer
• Approximate EMF: 1.5 V

Lead Storage Battery

• Secondary cell
• Pb and PbO₂ are the electrodes
• H₂SO₄ is the electrolyte
• Approximate EMF: 2.0 V per cell
• PbSO₄ forms during discharge
• H₂SO₄ concentration decreases during discharge
• Six cells connected in series give approximately 12 V

These are the major concepts covered in the supplied 20-question practice material.

Practice Questions: Leclanché Cell & Lead Storage Battery

Now that you have studied the concepts, test your understanding with the 20-question practice set based on Leclanché Cell and Lead Storage Battery.

📥 Download the Leclanché Cell & Lead Storage Battery Practice PDF

The practice set covers electrolytes, electrodes, EMF, primary and secondary cells, discharge and charging reactions, PbSO₄ formation, H₂SO₄ concentration and series connection of cells.

Try answering the questions yourself before checking the answer key.

Final Revision

The most important points to remember are:

Leclanché Cell:
NH₄Cl → Electrolyte
Zn → Anode
MnO₂ → Depolarizer
1.5 V → Approximate EMF

Lead Storage Battery:
Pb/PbO₂ → Electrodes
H₂SO₄ → Electrolyte
2.0 V → Approximate EMF per cell
PbSO₄ → Formed during discharge
H₂SO₄ concentration → Decreases during discharge
6 cells in series → Approximately 12 V

A clear understanding of these points, followed by regular MCQ practice, can make this part of Electrochemistry much easier to revise for the UP PGT Chemistry exam.

Prepare for UP TGT Science with The Rasayanam

Want structured guidance for your UP TGT Science preparation?

Join The Rasayanam today and prepare with focused study material, practice questions, PYQs, and exam-oriented guidance to help you crack the UP TGT Science exam.

Start your preparation with The Rasayanam today.

Along with video lectures and practice questions, choosing the right study material is important for effective preparation.

📱 WhatsApp/Call: +91-8285162819
✉️ The Rasayanam: therasayanam@gmail.com
▶️ YouTube: @therasayanam
📲 App: Available on Google Play (Android) and via the Classplus app (iOS)