Question

The standard electrode potentials ( $\text{ E}_{{{\text{M}}^{\text{+}}}\text{/M }}^{\text{0}}$ ) of four metals A, B, C, and D are $\text{ }-\text{1}\text{.2 V }$, $\text{ 0}\text{.6 V }$, $\text{ 0}\text{.85 V }$ and $\text{ }-0.\text{76 V }$, respectively. The increasing sequence of deposition of metals on applying potential is
a) A, C B, D
b) B, D, C, A
c) C, B, D, A
d) D, A, B, C

Answer 1

Hint: The standard potential is the potential difference between the electrodes at the standard condition say the temperature is $\text{ 298 K }$ and pressure $\text{ 1 atm }$ dipped in the electrolyte solution of 1 molar. The species which have the positive value of electrode potential can easily accept the electron and deposit easily. Species that have a negative value of potential are more likely to donate the electron.

Complete step by step solution:
The standard electrode potential is used to measure the potential required for the equilibrium. The potential difference between the electrode and electrolyte is known as the potential of the electrode. However, when the 1 molar or 1 unit concentration of the electrolyte is placed between electrode s, then the electrode potential developed at the electrodes is called the standard electrode potential. It is represented as $\text{ }{{\text{E}}^{\text{0}}}\text{ }$.
The standard potential is the potential difference between the electrodes at the standard condition say the temperature is $\text{ 298 K }$ and pressure $\text{ 1 atm }$ dipped in the electrolyte solution of 1 molar.
The standard potential has a great significance in determining whether the species undergoes oxidation or reduction.
The standard electrode potential of the number of electrodes is arranged in a series .This is known as the electrochemical series.
The magnitude of the $\text{ }{{\text{E}}^{\text{0}}}\text{ }$ measures the tendency of the metal to reduce.
The higher positive value of the electrode potential means that it has a greater tendency to accept the electrons and convert from oxidized form to reduced form.
However, the greater negative value means it tends to donate an electron and convert from reduced form to oxidized form.
The metal which has a higher positive electrode potential preferably reduced at the electrode and deposits it.
Here, we have given the 4 metals which have electrode potentials as follows,

Metal	Standard electrode potential
A	$\text{ }-\text{1}\text{.2 V }$
B	$\text{ 0}\text{.6 V }$
C	$\text{ 0}\text{.85 V }$
D	$\text{ }-0.\text{76 V }$

The A has the highest negative potential of$\text{ }-\text{1}\text{.2 V }$, thus it is deposited easily. The order of electrode potential to deposition on the electrode on applying potential is given as: $\text{ C }>\text{ B }>\text{ D }>\text{ A }$

Hence, (c) is the correct option.

Note: The standard electrode potential values are said to be on the hydrogen scale since these are determined using the standard hydrogen electrode as the reference electrode. The value of the standard electrode potential for hydrogen is taken as the zero. The electrode potential has a wide application in the determination of oxidizing and reducing the strength of the species. One which has the negative value is more likely to act as a reducing agent and on a more positive sign as the oxidizing agent.