Question

One thing being equal, the EMF of a Deniell cell may be increased by
A. Keeping low temperature
B. Using large copper electrodes
C. Using large Zinc electrodes
D. Decreasing concentration of $[C{u^{ + 2}}]$ ions

Answer 1

Hint - We know that the Deniell cell is an electrochemical series, by keeping the low temperature, the EMF of a Deniell cell may be increased. As the reactants in the cell approaches the equilibrium concentration, voltage drops to zero. There are different factors which affect the equilibrium.

Complete step by step answer:
The Nernst equation predicts the voltage which has a linear increase with the temperature and this also changes with the$ln$of equilibrium constant. $lnK$from the Nernst equation decreases with temperature eventually as the reaction is at equilibrium and at some temperature where voltage is zero.
For Deniell cell,
We can write the electrochemical reaction as
$Z{n^ + } + C{u^{ + 2}} \to Z{n^{ + 2}} + Cu$
Therefore,
${E_{cell}} = E{^\circ _{cell}} - \dfrac{{RT}}{{nF}}\ln \dfrac{{[Z{n^{ + 2}}]}}{{[C{u^{ + 2}}]}}$

So, as temperature decreases and increases in $[C{u^{ + 2}}]$, the EMF of the cell may increase.

Additional information: Deniell cell is a form of the galvanic cell. It is composed of copper and zinc electrodes immersed in the zinc sulfate and copper sulfate solutions. Two half cells are connected with each other using the salt bridge. In this, copper acts as cathode and zinc acts as electrode as anode. The Zn metal occupies the top position in the electrochemical series when compared with the Cu metal, which has the higher value of the oxidation potential of a metal. Hence, zinc undergoes regular oxidation consequently after which two electrons and a zinc ion is generated. These electrodes acquire a negative potential due to which the release of electrons when compared to the other electrode is known as an anode.

Note : we must know that the EMF or electromotive force of a cell is the maximum potential difference between the two electrodes of the cell. The EMF of a cell is mainly used to identify whether an electrochemical cell is a galvanic cell or different.