NIELIT University(Govt. of India Institution) B.Tech/ M.Tech
ApplyLast Date to Apply : 15th September | Campuses in Agartala, Aizawl, Ajmer, Aurangabad, Calicut, Imphal, Itanagar, Kohima, Gorakhpur, Patna & Srinagar
Nernst Equation, Nernst Equation for Fuel Cell, Equilibrium Constant Through Nernst Equation are considered the most difficult concepts.
75 Questions around this concept.
In a cell that utilizes the reaction
addition of to cathode compartment, will
An oxidation-reduction reaction in which 4 electrons are transferred has a. of
at
. Find the value of
This equation gives the relationship between electrode potential and the concentration of ions in the solution. In other words, it shows the dependency of electrode potential on the concentration of the ions with which the electrode is reversible.
For a single electrode involving the reduction process,
The reaction quotient Q is defined as
Now, we learnt in thermodynamics that
..(1)
Where
and
So, substituting these values is (1),
This is the Nernst equation which helps us to calculate the non-standard EMF of any Half cell. It can be extended to full of any half cell. It can be extended to full cell which we will be learning later.
In using the above equation, the following facts should be kept in mind.
In the full cell both the oxidation and reduction reactions occur simultaneously. Thus, the full cell can be represented as follows:
The electrode potential values for oxidation and reduction are as follows:
At Anode:
At Cathode:
Thus the complete cell reaction is the addition of both anode and cathode reaction. It given as below:
Thus the reaction quotient(Q) can be given as follows:
where c1 and c2 are the concentrations of Mx+ and Nx+ respectively.
The standard potential of cell is given as:
At T = 298K, Nernst equation is given as follows:
where n is the number of electrons exchanged.
Thus the Nernst equation for the full cell is given as follows:
If the circuit in Daniell cell is closed then we note that the reaction
takes place and as time passes, the concentration of Zn2+ keeps on increasing while the concentration of Cu2+ keeps on decreasing. At the same time, the voltage of the cell as read on the voltmeter keeps on decreasing. After some time, we shall note that there is no change in the concentration of Cu2+ and Zn2+ ions and at the same time, voltmeter gives zero reading. This indicates that equilibrium has been attained. In this situation the Nernst equation may be written as:
Alternatively
At equilibrium,
Thus, the above equation gives a relationship between the equilibrium constant of the reaction and standard potential of the cell in which that reaction takes place. Thus, equilibrium constants of the reaction, difficult to measure otherwise, can be calculated from the corresponding Eo value of the cell.
"Stay in the loop. Receive exam news, study resources, and expert advice!"