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What is the standard electrode potential (E°) and how is it measured?
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The standard electrode potential (E°) is defined as the potential of a half-cell under standard conditions (1M ion concentration, 298K, and 1 bar pressure for gases). It is measured using the Standard Hydrogen Electrode (SHE) as a reference, which has an E° of 0V.
Provide the Nernst equation and its simplified form at 298K.
The Nernst equation is E = E° - (RT/nF) lnQ. At 298K, it simplifies to E = E° - (0.059/n) logQ.
What is corrosion, and how can it be prevented?
Corrosion is the slow conversion of metals into undesirable compounds through oxidation, such as the rusting of iron. It can be prevented through methods like barrier protection (painting, coating) and sacrificial protection (using more reactive metals as anodes).
Explain the working principle of a hydrogen-oxygen fuel cell.
A hydrogen-oxygen fuel cell converts chemical energy directly into electrical energy by the reaction of hydrogen and oxygen to produce water. It typically has an efficiency of about 70%.
Describe the role of the salt bridge in a Daniell cell.
The salt bridge in a Daniell cell allows the flow of ions between the two half-cells to maintain electrical neutrality, enabling the cell to produce a continuous electrical current.
How does the Nernst equation help in calculating the electrode potential under non-standard conditions?
The Nernst equation adjusts the standard electrode potential (E°) for actual conditions (non-standard concentrations, pressures, and temperatures), providing the actual electrode potential (E) using the reaction quotient (Q).
State Faraday's first and second laws of electrolysis.
First Law: The amount of substance deposited at an electrode is directly proportional to the quantity of electric charge passed. Second Law: The amounts of different substances deposited by the same quantity of electricity are proportional to their equivalent weights.
What is the relationship between EMF (Electromotive Force) and Gibbs free energy change (ΔG°)?
The relationship is given by ΔG° = -nFE°, where F is Faraday's constant (96,487 C/mol).
Distinguish between primary and secondary batteries with examples.
Primary batteries cannot be recharged and are used until the chemical reagents are exhausted (e.g., Dry cell, Mercury cell). Secondary batteries can be recharged and reused multiple times (e.g., Lead-acid battery, Ni-Cd battery).
Write the oxidation and reduction reactions occurring in the Daniell cell.
Anode (Oxidation): Zn → Zn²⁺ + 2e⁻ Cathode (Reduction): Cu²⁺ + 2e⁻ → Cu
Differentiate between conductivity (κ) and molar conductivity (Λm) and provide their relationship.
Conductivity (κ) is the measure of a solution’s ability to conduct electricity, while molar conductivity (Λm) is the conductivity per unit concentration of the solution. Λm = κ / C, where C is the concentration.
What are some electrochemical applications in acid-base titrations?
In acid-base titrations, electrochemical principles can locate the equivalence point by measuring changes in electrode potential as the titrant is added to the analyte.
In the context of electrochemical series, what characteristics do strong oxidants and strong reductants exhibit?
Strong oxidants have higher standard electrode potentials (E°), indicating a greater tendency to accept electrons, e.g., Fluorine. Strong reductants have lower E° values, indicating a greater tendency to donate electrons, e.g., Lithium.
How do you calculate the cell potential using standard electrode potentials?
The cell potential (E°cell) is calculated using the formula: E°cell = E°cathode - E°anode.
What is the main difference between a galvanic cell and an electrolytic cell in terms of free energy?
In a galvanic cell, the free energy change (ΔG) is negative and the reaction is spontaneous, producing electricity. In an electrolytic cell, ΔG is positive, and the reaction is non-spontaneous, requiring an external source of electrical energy.
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