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Find the emf of the following cell reaction, given E Cr 3 + / cr 2 + 0 = - 0 . 72   V and E Fe 2 + / Fe = 0 - 0 . 42   V at 25 ° C is Cr Cr 3 + ( 0 . 1 M ) ‖ Fe 2 + ( 0 . 1 M ) Fe

Options

  1. A0.30 V
  2. B0.25 V
  3. C1.14 V
  4. D1.56 V

Correct answer

A. 0.30 V

Step-by-step solution

The given cell is: Cr Cr 3 + ( 0 . 1 M ) ‖ Fe 2 + ( 0 . 1 M ) Fe The half reactions can be written as: Cr → Cr 3 +   + 3 e - 1                   E °   =   - 0 . 72 V Fe 2 + + 2 e - 1   →   Fe               E °   =   - 0 . 42 V The full reaction of the operating cell is: 3 Fe 2 + + 2 Cr   →   2 Cr 3 + + 3 Fe Now, emf of the cell reaction is E ° cell &#160

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