CBSE Class 12 Chemistry Electrochemistry Quiz

CBSE Class 12 Chemistry: Electrochemistry

In your CBSE Class 12 chemistry curriculum, electrochemistry is a pivotal topic that explores the transformations of chemical energy into electrical energy and vice versa. This field, while complex, is integral to understanding the practical applications of redox reactions in real-world scenarios, such as batteries, corrosion, and electroplating.

Redox Reactions

Redox reactions, short for oxidation and reduction reactions, are the foundation of electrochemistry. In a redox reaction, one species loses electrons (oxidation) while another gains electrons (reduction). In electrochemistry, these reactions are studied in terms of half-reactions, balancing oxidation and reduction potentials to yield a cell potential.

Galvanic Cells and Electrolytic Cells

A galvanic cell is a device that converts chemical energy into electrical energy through a spontaneous redox reaction, while an electrolytic cell does the opposite, converting electrical energy into chemical energy. Both types of cells use electrodes, separators, and electrolytes to enable these transformations.

Nernst Equation and Cell Potential

The Nernst equation describes the relationship between cell potential, temperature, and the concentrations of the species involved in a redox reaction. This relationship is used to calculate cell potentials under nonstandard conditions. The standard cell potential, on the other hand, is the cell potential under standard conditions, which include the use of standard states for all species and a temperature of 298.15 K.

Faraday's Laws

Faraday's laws of electrolysis provide a quantitative relationship between the amount of electricity passed through an electrolytic cell and the amount of substance produced or consumed during the process. These laws are used to calculate the molar mass of unknown substances and to determine the stoichiometry of electrochemical processes.

Applications of Electrochemistry

Some of the applications of electrochemistry include:

1. Batteries: Electrochemical cells are used to store energy in the form of chemical potential, which can be released as electrical energy when needed.

2. Corrosion: Corrosion is an electrochemical process where the degradation of a metal occurs as a result of oxidation and reduction reactions.

3. Electroplating: A metal coating is applied to another metal substrate using an electrochemical deposition process.

4. Fuel cells: Fuel cells use redox reactions to generate electrical energy from chemical fuels, such as hydrogen and oxygen gases.

5. Electroanalysis: Electroanalytical techniques are used to study the properties of chemical species in solution, such as their concentrations, redox potentials, and reaction rates.

Solved Examples

1. Calculate the cell potential of a galvanic cell containing a half-cell with zinc (Zn) as the anode and the other half-cell with copper (Cu) as the cathode, both under standard conditions.

[ \begin{aligned} E^{o}{\text{cell}} &= E^{o}{\text{cathode}} - E^{o}_{\text{anode}} \ &= (0.337 \text{ V}) - (-0.763 \text{ V}) \ &= 1.10 \text{ V} \end{aligned} ]

2. Calculate the theoretical capacity of a 12 V, 5 Ah lead-acid battery.

[ \begin{aligned} \text{Theoretical capacity (C)} &= \frac{\text{Potential} \times \text{Charge}}{\text{Faraday's constant}} \ &= \frac{(12 \text{ V}) \times (5 \text{ Ah})}{96485 \text{ C mol}^{-1}} \ &= 0.0521 \text{ mol} \ \text{Molar mass of PbSO}{4} &= 207.2 \text{ g mol}^{-1} \ \text{Theoretical mass of PbSO}{4} &= 0.0521 \text{ mol} \times 207.2 \text{ g mol}^{-1} \ &= 10.8 \text{ g} \end{aligned} ]

3. Calculate the reduction potential of Fe(III) to Fe(II) under standard conditions.

[ \begin{aligned} E^{o}{\text{red}} &= -E^{o}{\text{ox}} \ &= -(-0.77 \text{ V}) \ &= 0.77 \text{ V} \end{aligned} ]

Conclusion

In CBSE Class 12 Chemistry, electrochemistry provides students with a deep understanding of the fundamental principles and applications of redox reactions. By exploring topics like cell potentials, Faraday's laws, and applications of electrochemistry, students will gain vital skills required for the study of chemical and physical sciences, as well as for understanding the real-world applications of electrochemical processes.