Question

When a battery is connected to a Daniell cell (galvanic cell) such that the cell reaction becomes reversed (non-spontaneous).
Which of the following is/are correct?

• A. $Zn$ rod will start to deteriorate
• B. $Cu$ rod will start to deteriorate
• C. $Z{n}^{2+}$ reduces and gets deposited on $Zn$ rod
• D. $C{u}^{2+}$ reduces and gets deposited on $Cu$ rod

Answer 1

Answer: (B), (C)

$Z{n}^{2+}$ reduces and gets deposited on $Zn$ rod

Galvanic cell is also known as Voltaic cell. It converts the chemical energy liberated during the reaction to electrical energy. The chemical reaction will be a spontaneous reaction.
Daniell is a galvanic cell.

In Daniell cell,
At anode: $Zn\text{rod in}ZnS{O}_4\text{solution}$
At cathode: $Cu\text{rod in}CuS{O}_4\text{solution}$
$Zn\left(s\right)\to Z{n}^{2+}\left(aq\right)+2e^{-}\left(\text{at anode}\right)$
$C{u}^{2+}\left(aq\right)+2e^{-}\to Cu\left(s\right)\left(\text{at cathode}\right)$
Thus, the redox reaction of the Daniell cell is
$Zn\left(s\right)+C{u}^{2+}\left(aq\right)\to C{u}^{2+}\left(aq\right)+Cu\left(s\right)$

When an external battery is connected to the circuit, the current will flow from battery to the galvanic cell and reverse the process.

By reversing the process,
Thus, $Cu$ rod will starts to deteriorate
$Cu\left(s\right)\to C{u}^{2+}\left(aq\right)+2e^{-}$

$Z{n}^{2+}$ will get reduced and deposit on the zinc rod.
$Z{n}^{2+}\left(aq\right)+2e^{-}\to Zn\left(s\right)$