AP EAMCET202119 Aug 2021Evening ShiftChemistryElectrochemistryActual
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
- A0.30 V
- B0.25 V
- C1.14 V
- 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