Exercises - 2.10 | 2. Electrochemistry | CBSE Grade 12 Chemistry Part 1
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Introduction to Electrochemical Cells

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0:00
Teacher
Teacher

Welcome, class! Today, we're going to recap the basics of electrochemical cells. Can anyone tell me what the main difference is between galvanic and electrolytic cells?

Student 1
Student 1

Galvanic cells convert chemical energy into electrical energy, while electrolytic cells do the opposite, using electrical energy to drive non-spontaneous reactions.

Teacher
Teacher

Absolutely right! We can remember this with the acronym 'GE sheet'- Galvanic Energy and electrolytic as Electrical. Does anyone have an example of each?

Student 2
Student 2

The Daniell cell is a galvanic cell, right? And an example of an electrolytic cell would be the electrolysis of water?

Teacher
Teacher

Perfect! Now, let's delve deeper and explore how we calculate the standard potentials for these cells.

Calculating Cell Potentials

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0:00
Teacher
Teacher

Let's discuss how to calculate the standard cell potential. Can someone remind me of the formula?

Student 3
Student 3

The cell potential, EαΆ¦, is calculated using the formula EαΆ¦ = EαΆ¦αΆ¦Cathode - EαΆ¦αΆ¦Anode!

Teacher
Teacher

Great memory! To reinforce this, let's solve a problem together. If we have a Zn/Cu cell, where Eᢦ for the Cu²⁺/Cu is 0.34 V and Zn²⁺/Zn is -0.76 V, what is the overall cell potential?

Student 4
Student 4

It would be EαΆ¦ = 0.34 - (-0.76), which equals 1.10 V!

Teacher
Teacher

Fantastic! Just remember, a positive cell potential indicates a spontaneous process.

Nernst Equation Application

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0:00
Teacher
Teacher

Now let's discuss how to use the Nernst equation. Who can remind us how it looks?

Student 1
Student 1

E = EαΆ¦ - (RT/nF) * ln(Q) is the Nernst equation!

Teacher
Teacher

Exactly! For practical application, if the concentration of Cu²⁺ is 0.001 M in our previous example, how would we calculate E?

Student 3
Student 3

We'd need R and F values, and the number of moles of electrons, n, which is 2 for Zn to Cu.

Teacher
Teacher

Perfect! So if we plug everything in, what do we find?

Conductivity and Molar Conductivity

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0:00
Teacher
Teacher

Next, conductivity is important for electrolyte solutions. Can anyone explain how we differentiate between conductivity and molar conductivity?

Student 2
Student 2

Conductivity is the ability of a solution to conduct electricity, while molar conductivity relates this ability to the concentration of the electrolyte.

Teacher
Teacher

Correct! To remember this, think 'conductivity is general, while molar conductivity is specific to moles.' Let's tackle an example: if we have 0.01 M KCl and its conductivity is given as 0.0141 S/cm, how do we derive the molar conductivity?

Student 4
Student 4

We can use the formula Ξ› = ΞΊ/c, where ΞΊ is conductivity and c is concentration!

Teacher
Teacher

Excellent! And this will give us valuable information about how the electrolyte behaves in solution.

Faraday's Laws and Electrolysis

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0:00
Teacher
Teacher

Finally, let’s focus on electrolysis and Faraday’s laws. Can anyone summarize Faraday's first law?

Student 1
Student 1

The mass of substance altered at the electrodes is proportional to the quantity of electricity passed.

Teacher
Teacher

Correct! Faraday’s second law states that the amounts of different substances deposited will be proportional to their equivalent weights. This can be summarized with the phrase 'Mass = Current Γ— Time.' If we pass 2.5 A for 5 minutes, what would be the mass of copper deposited?

Student 3
Student 3

Using the formula m = (Q Γ— M)/(n Γ— F), where we calculate Q first, we find the mass.

Teacher
Teacher

Exactly! And it’s crucial to understand these concepts because they have practical applications in industries.

Introduction & Overview

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Quick Overview

This section covers a series of exercises aimed at reinforcing the fundamental concepts of electrochemistry, including calculations involving galvanic and electrolytic cells.

Standard

The exercises focus on practical applications of electrochemical principles, guiding students through various problem-solving scenarios involving calculations of cell potential, electrode reactions, and practical applications in galvanic and electrolytic cells.

Detailed

Detailed Summary

In this section, we explore exercises that allow students to apply electrochemical concepts previously studied, particularly those related to galvanic and electrolytic cells. The exercises encompass a range of difficulties, from basic calculations involving standard electrode potentials to more complex applications such as Nernst equation scenarios and measurements of conductivity and molar conductivity. These exercises aim to foster a deep understanding of electrochemical processes and their quantitative aspects. Students are encouraged to engage with the content actively, harnessing applicable skills required for solving both theoretical and practical problems in electrochemistry, ultimately reinforcing their knowledge and conceptual clarity.

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Audio Book

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Objectives of Electrochemistry

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  • Describe an electrochemical cell.
  • Differentiate between galvanic and electrolytic cells.
  • Apply Nernst equation for calculating the emf of galvanic cell and define standard potential of the cell.
  • Derive relation between standard potential of the cell, Gibbs energy of cell reaction and its equilibrium constant.
  • Define resistivity (ρ), conductivity (ΞΊ) and molar conductivity (Ξ›) of ionic solutions.
  • Differentiate between ionic (electrolytic) and electronic conductivity.
  • Describe the method for measurement of conductivity of electrolytic solutions and calculation of their molar conductivity.
  • Justify the variation of conductivity and molar conductivity of solutions with change in their concentration.
  • Define Λ° (molar conductivity at zero concentration or infinite dilution).
  • Enunciate Kohrausch law and learn its applications.
  • Understand quantitative aspects of electrolysis.
  • Describe the construction of some primary and secondary batteries and fuel cells.
  • Explain corrosion as an electrochemical process.

Detailed Explanation

The objectives of electrochemistry encompass understanding electrochemical cells, which are devices that convert chemical energy into electrical energy (as seen in galvanic cells) and the opposite in electrolytic cells. Students will learn to apply mathematical models such as the Nernst equation, which helps calculate the electric potential of these cells based on concentration. The section also covers fundamental definitions, like resistivity and conductivity, and their practical implications in real-world applications such as batteries and corrosion processes.

Examples & Analogies

Think of a battery as a 'power plant' for electronic devices. Just as power plants convert energy sources to produce electricity for homes, batteries convert stored chemical energy into electrical energy to power devices like remote controls or smartphones. Understanding these conversions helps us appreciate how things like recharging batteries are similar to renewable energy practices.

Construction and Functioning of Electrochemical Cells

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We had studied the construction and functioning of Daniell cell. This cell converts the chemical energy liberated during the redox reaction:

Zn(s) + Cu2+(aq) β†’ Zn2+(aq) + Cu(s) (1)

to electrical energy and has an electrical potential equal to 1.1 V when concentrations of Zn2+ and Cu2+ ions are unity (1 mol dm–3). Such a device is called a galvanic or a voltaic cell. If an external opposing potential is applied in the galvanic cell, and increased slowly, we find that the reaction continues to take place till the opposing voltage reaches the value 1.1 V when no current flows through the cell. Any further increase in the external potential again starts the reaction but in the opposite direction.

Detailed Explanation

The Daniell cell is a common example of a galvanic cell that generates electricity through a spontaneous redox reaction. It involves zinc and copper electrodes in an electrolyte solution. When no external voltage is applied, the cell produces potential via the oxidation of zinc and reduction of copper ions. However, if an external voltage opposes this reaction and matches the cell's potential (1.1 V), current ceases. This principle of operation is fundamental to understanding how batteries work in daily electronic devices.

Examples & Analogies

Imagine a water fountain where water flows down freely (representing the spontaneous reaction of the galvanic cell). If we try to pump water back up to the top (applying external voltage), we reach a point where the pump’s pressure matches the water flow downwards (1.1 V). When this happens, the fountain stops flowing, just like current stops in the galvanic cell when opposing voltage equals its potential.

Types of Electrochemical Cells

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We will study two major types of electrochemical cells – galvanic cells, which convert chemical energy into electrical energy through spontaneous reactions, and electrolytic cells, which use electrical energy to drive non-spontaneous reactions. Understanding these differences provides insight into practical applications such as batteries and electrolysis.

Detailed Explanation

In this section, students will differentiate between galvanic and electrolytic cells. Galvanic cells, like batteries, harness spontaneous chemical reactions to create electricity, while electrolytic cells require external energy to drive reactions that don't occur naturally. Recognizing these fundamental differences is crucial for grasping their applications in energy storage and chemical manufacturing.

Examples & Analogies

Think of a waterfall as a galvanic cell, where water flows down naturally to generate power, like a hydroelectric plant. An electrolytic cell is like a pump that moves water against gravity; it requires energy (electricity) to push the water back up. Both systems are vital for generating and managing energy in our world, from powering homes to running industrial processes.

Definitions & Key Concepts

Learn essential terms and foundational ideas that form the basis of the topic.

Key Concepts

  • Electrochemical Cells: Devices that convert chemical energy into electrical energy or vice versa.

  • Galvanic Cell: A type of electrochemical cell that runs spontaneously.

  • Electrolytic Cell: Requires an external power source to operate.

  • Nernst Equation: Determines cell potential based on conditions.

  • Conductivity: How well a solution can conduct electricity based on ion mobility.

  • Molar Conductivity: Measures conductivity relative to concentration.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

  • The Daniell cell is an example of a galvanic cell.

  • The electrolysis of water is a typical example of an electrolytic cell.

  • Using Nernst equation, we can calculate potential in non-standard conditions.

  • Cooking salt (NaCl) in solution increases its conductivity due to ion dissociation.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎡 Rhymes Time

  • In a galvanic cell, chemicals meet, producing currents, isn't that neat?

πŸ“– Fascinating Stories

  • Imagine a waterwheel powered by rain – that’s a galvanic cell using a drain to create energy from a chemical chain!

🧠 Other Memory Gems

  • Remember: 'GEE' for Galvanic Energy, to distinguish it from Electric Energy in electrolytic cells.

🎯 Super Acronyms

N.E.R.N.S.T means Nurturing Electrical Reactions, Not Solving Theoretical.

Flash Cards

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Glossary of Terms

Review the Definitions for terms.

  • Term: Electrochemical Cell

    Definition:

    A device that transforms chemical energy into electrical energy or vice versa.

  • Term: Galvanic Cell

    Definition:

    An electrochemical cell that generates electrical energy from spontaneous chemical reactions.

  • Term: Electrolytic Cell

    Definition:

    An electrochemical cell that utilizes electrical energy to drive non-spontaneous chemical reactions.

  • Term: Cell Potential

    Definition:

    The measure of the voltage produced by an electrochemical cell.

  • Term: Nernst Equation

    Definition:

    An equation that relates the cell potential to the concentrations of the reactants and products in the electrochemical cell.

  • Term: Conductivity

    Definition:

    The ability of a solution to conduct electrical current, dependent on the ion concentration.

  • Term: Molar Conductivity

    Definition:

    The conductivity of a solution per mole of solute.