Question

Two statements are given about the galvanic cell shown below
Statement I: Current flows from Cu electrode to Zn electrode
Statement II: With increase in time the mass of Zn electrode increases and mass of Cu electrode decreases
Correct answer is

• A. Both statements I and II are correct
• B. Both statements I and II are not correct
• C. Statement I is correct and statement II is not correct
• D. Statement I is not correct and statement II is correct

Hint:

Remember:
If $E_{\text{ext}} \lt 1.1\text{ V}$, the cell acts as a galvanic cell (Zn is anode, Cu is cathode).
If $E_{\text{ext}} = 1.1\text{ V}$, no reaction occurs and no current flows.
If $E_{\text{ext}} \gt 1.1\text{ V}$, the cell reactions are reversed and it behaves as an electrolytic cell (Cu is anode, Zn is cathode).

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
This question is about a classic zinc-copper galvanic cell (Daniell cell) operating with an external potential $E_{\text{ext}} \lt 1.1\text{ V}$.
We need to determine the direction of conventional current and changes in the mass of the electrodes over time.

Step 2: Key Formula or Approach:
The standard potential of a zinc-copper cell is $1.1\text{ V}$.
When $E_{\text{ext}} \lt 1.1\text{ V}$, the cell functions normally as a galvanic cell:
At the anode (zinc electrode): Oxidation occurs ($\text{Zn} \rightarrow \text{Zn}^{2+} + 2e^{-}$).
At the cathode (copper electrode): Reduction occurs ($\text{Cu}^{2+} + 2e^{-} \rightarrow \text{Cu}$).

Step 3: Detailed Explanation:

• Evaluation of Statement I:
In a functioning galvanic cell with $E_{\text{ext}} \lt 1.1\text{ V}$:
Electrons flow from the zinc anode (negative electrode) to the copper cathode (positive electrode) through the external circuit.
The conventional electric current flows in the opposite direction of the electron flow: from the copper (Cu) cathode to the zinc (Zn) anode.
Thus, Statement I is correct.

• Evaluation of Statement II:
During cell operation, zinc atoms at the anode undergo oxidation and dissolve into the solution as $\text{Zn}^{2+}$ ions, causing the mass of the zinc electrode to decrease over time.
Copper ions ($\text{Cu}^{2+}$) in the solution gain electrons and deposit as solid copper on the cathode, causing the mass of the copper electrode to increase over time.
Statement II asserts the exact opposite, making it incorrect.

• Therefore, Statement I is correct, and Statement II is incorrect.


Step 4: Final Answer:
Statement I is correct and Statement II is not correct.