Electrochemistry

The electromotive force (emf) of an electrochemical cell is calculated using the Nernst equation: where is the standard cell potential, is the number of electrons transferred, and is the reaction quotient.
Step 1: Identify the cell reaction The cell notation is . - Anode (left, oxidation): - Cathode (right, reduction): Balance the electrons by multiplying the cathode reaction by 2: Overall cell reaction: Thus, (2 electrons transferred).
Step 2: Write the reaction quotient For the reaction , the reaction quotient is: (Solids have activity = 1.) Given: - -
Step 3: Apply the Nernst equation Given , , and at 298 K ( ): Calculate . Then: Rounding to two decimal places, .
Step 4: Match with options The closest option is (C) .

The cell constant ( ) of an electrolytic cell is defined as the ratio of the distance between electrodes ( ) to the cross-sectional area of the electrodes ( ): It has units of or .
Step 1: Relate to conductivity and resistance
- Conductivity ( ): Measures a solution’s ability to conduct electricity ( ).
- Resistance ( ): Measured in ohms ( ).
- Conductance ( ): Inverse of resistance, , in siemens ( ).
The relationship is: Thus, cell constant equals conductivity times resistance.
Step 2: Analyze options
- (A) Conductivity Resistance: Correct, as .
- (B) Conductivity / Resistance: Incorrect, as , which has different units.
- (C) : Incorrect, as , not .
- (D) (A) and (C): Incorrect, as (C) is wrong.
Step 3: Conclusion
Option (A) is correct, but since the question implies a single correct answer and option (D) incorrectly pairs (A) and (C), we note that (A) is the most accurate.