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Calculate the emf of the cell at 25 °C: Zn(s) | (0.01 M) || (1.0 M) | Cu(s). Standard potentials: = -0.76 V, = +0.34 V. Use the Nernst equation.

easy MCQ 2 marks Class 12 · Chemistry · Electrochemistry
  1. 1.05 V
  2. 1.16 V
  3. 0.99 V
  4. 1.21 V
Answer
1.16 V

The correct answer is 1.16 V — Round the result to two decimal places.

Step-by-step solution

  1. Write the overall cell reaction: Zn(s) + + Cu(s).
  2. Identify that the number of electrons transferred, n, is 2.
  3. Calculate the standard cell potential: E°_cell = = 0.34 - (-0.76) = 1.10 V.
  4. Apply the Nernst equation: E = E° - (0.0592/n) log([]/[]).
  5. Insert the concentrations: log([]/[]) = log(0.01/1) = log(0.01) = -2.
  6. Compute the correction term: (0.0592/2)(-2) = -0.0592 V, so E = 1.10 - (-0.0592) = 1.1592 V.
  7. Round the result to two decimal places.
Common mistake: Using the concentration quotient as []/[] instead of the correct ratio

Concept tested: Nernst equation for cell potential

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