Resonance Chemistry Electro Chemistry

Resonance in Chemistry & Electrochemistry – Explained

 1. Resonance in Chemistry

Resonance is a concept in organic and inorganic chemistry that explains the delocalization of electrons within a molecule.

 Definition of Resonance:

• When a molecule cannot be represented by a single Lewis structure but instead exists as a hybrid of multiple structures, it is said to exhibit resonance.
• The actual structure is a resonance hybrid, which is more stable than any of the individual contributing structures.

 Example of Resonance:

1⃣ Benzene (C₆H₆):

• It has two resonance structures with alternating single and double bonds.
• The actual structure is a hybrid, where all bond lengths are equal.

2⃣ Carbonate Ion (CO₃²⁻):

• Three equivalent resonance structures exist.
• The negative charge is delocalized over three oxygen atoms.

Key Idea: Resonance stabilizes molecules by spreading out charge and lowering energy.

 2. Electrochemistry

Electrochemistry is the branch of chemistry that studies the relationship between electricity and chemical reactions.

 Key Concepts in Electrochemistry

Redox Reactions (Oxidation-Reduction)

• Oxidation: Loss of electrons (e.g., Zn → Zn²⁺ + 2e⁻)
• Reduction: Gain of electrons (e.g., Cu²⁺ + 2e⁻ → Cu)

Electrochemical Cells:

• Galvanic (Voltaic) Cells → Convert chemical energy to electrical energy. (e.g., batteries)
• Electrolytic Cells → Use electrical energy to drive non-spontaneous reactions. (e.g., electrolysis)

Nernst Equation:

• Used to calculate the cell potential (E) at non-standard conditions.
• Formula: E = E⁰ - (0.0591/n) log [Products] / [Reactants]

Faraday’s Laws of Electrolysis:

• 1st Law: The amount of substance deposited is proportional to charge.
• 2nd Law: Mass of substances deposited is proportional to their equivalent weight.

 Applications of Resonance & Electrochemistry

Resonance: Helps explain acid strength, stability, and color of compounds. (e.g., resonance in phenol, aniline, and dyes)
Electrochemistry: Used in batteries, corrosion prevention, metal extraction, and fuel cells.

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Resonance Chemistry Electro Chemistry

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UNIT-I ELECTROCHEMISTRY

Electrochemistry

Resonance Chemistry Electrochemistry Notes are widely used by students preparing for IIT-JEE, NEET, and Class 11–12 Boards. Below is a summarized overview of Electrochemistry based on standard Resonance Institute modules:

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Electrochemistry – Resonance Chemistry Summary

1. What is Electrochemistry?

Electrochemistry is the branch of chemistry that deals with the relationship between electrical energy and chemical changes, especially involving redox reactions.

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2. Important Terms:

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3. Electrochemical Cell (Galvanic Cell):

• Converts chemical energy → electrical energy

• Example: Daniel Cell

  • Anode (Zn): Zn → Zn²⁺ + 2e⁻ (oxidation)

  • Cathode (Cu): Cu²⁺ + 2e⁻ → Cu (reduction)

  • Electrons flow from Anode → Cathode

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4. Electrolysis:

• Uses electrical energy to bring about a chemical change (non-spontaneous reaction)

• Example: Electrolysis of NaCl

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5. Nernst Equation:

To calculate electrode potential under non-standard conditions:

E=E∘−0.0591nlog⁡[Products][Reactants]E = E^\circ - \frac{0.0591}{n} \log \frac{[ \text{Products} ]}{[ \text{Reactants} ]}E=E∘−n0.0591​log[Reactants][Products]​

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6. Standard Electrode Potential (E°):

• Measured under standard conditions (1M, 25°C)

• Reference: Standard Hydrogen Electrode (SHE) → E° = 0 V

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7. Electrochemical Series:

• A list of electrodes arranged by their standard electrode potentials.

• Helps predict:

  • Spontaneity of redox reactions

  • Strength of oxidizing/reducing agents

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8. Faraday’s Laws of Electrolysis:

First Law:

$$m=ZIt$$

Where,
m = mass of substance deposited,
Z = electrochemical equivalent,
I = current,
t = time

Second Law:
Masses of substances deposited are proportional to their equivalent weights.

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Tips for JEE/NEET Preparation:

• Understand redox reactions conceptually.

• Practice numericals based on Nernst Equation & Faraday's Laws.

• Memorize electrochemical series for reasoning questions.

• Use salt bridge concepts in diagram-based questions.

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Resonance Chemistry Electro Chemistry