JEE MainChemistryElectrochemistryMCQ+4 / −1
In a cell that utilises the reaction (s) + 2 (aq) (aq) + (g) addition of to cathode compartment, will
- Alower the E and shift equilibrium to the left
- Bincreases the E and shift equilibrium to the left
- Cincrease the E and shift equilibrium to the right
- DLower the E and shift equilibrium to the right
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Correct answer: C
- Identify the cell reaction
The cell reaction is
- Oxidation at anode:
- Reduction at cathode:
So, the cathode compartment contains ions.
- Write the reaction quotient
For the overall reaction,
since solid is omitted.
- Use the Nernst equation
At a given temperature,
Substituting :
- Effect of adding to cathode compartment
is a strong acid, so adding it increases .
From
if increases, then decreases.
Now from Nernst equation:
- If decreases, then decreases.
- Therefore, the term increases.
- Hence, cell emf increases.
- Effect on equilibrium
The reaction consumes :
By Le Chatelier’s principle, increasing concentration of a reactant () shifts the equilibrium to the right to consume added .
- Check options
- A: lower , shift left — incorrect
- B: increase , shift left — incorrect
- C: increase , shift right — correct
- D: lower , shift right — incorrect
- Final answer
The addition of to the cathode compartment will:
- increase the emf
- shift equilibrium to the right
So the correct option is C.
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