Electrochemistry

1. Energy Conversion: A Galvanic cell converts chemical energy into electrical energy (spontaneous reaction). An Electrolytic cell converts electrical energy into chemical energy (non-spontaneous reaction).
2. Polarity of Electrodes: In a Galvanic cell, the anode is negative and the cathode is positive. In an Electrolytic cell, the anode is positive and the cathode is negative.

The oxidation reaction of water is:
H O 2H + O + 2e
1. Moles of Water:
Molar mass of H O = 18 g/mol.
Moles of H O = moles.
2. Electrons required:
From the equation, oxidation of 1 mole of H O releases 2 moles of electrons.
So, 5 moles of H O will release moles of electrons.
3. Charge Calculation:
Charge of 1 mole of electrons (1 Faraday) 96487 C.
Total Charge = C.

Galvanisation is a specific metallurgical process used to protect steel or iron from rusting.
This involves applying a protective layer of Zinc (Zn) to the metal.
Zinc acts as a sacrificial anode, corroding in preference to the underlying iron.
Therefore, the correct coating material is Zinc.

Concept: Kohlrausch’s Law states that at infinite dilution, each ion contributes independently to the total molar conductivity of an electrolyte.
Answer:
Kohlrausch’s Law:
At infinite dilution, the molar conductivity of an electrolyte is equal to the sum of the individual ionic conductivities of its cations and anions. where is molar conductivity at infinite dilution, and , are ionic conductivities.
Explanation:
At infinite dilution, ions are so far apart that interionic interactions are negligible. Hence, each ion contributes independently to conductivity.
Applications:

• Calculation of molar conductivity of weak electrolytes: Using values of strong electrolytes.
• Determination of degree of dissociation: Helps in finding dissociation of weak electrolytes.
• Calculation of solubility of sparingly soluble salts.
• Determination of ionic conductivities.

Thus, Kohlrausch’s Law is important in understanding ionic behavior in dilute solutions.

Concept: The Nernst Equation relates the electrode potential of a cell to the standard electrode potential, temperature, and concentrations of reactants and products.
Answer:
For a general electrochemical reaction: The Nernst Equation is: where:

• = EMF of the cell
• = Standard EMF
• = Gas constant
• = Temperature in Kelvin
• = Number of electrons transferred
• = Faraday constant
• = Reaction quotient

At (298 K), the equation becomes: Example:
For a Daniell cell: By substituting concentration values, EMF can be calculated.