Question

Some of the batteries have alkaline electrolytes- (i) Nickel – Cadmium (ii) Mercury battery (iii) Modified Leclanche cell.
Cell potential is independent of $\left[ {O{H^ - }} \right]$ in:
A. i, ii
B. ii, iii
C. i, ii, iii
D. iii only

Answer 1

An electrochemical cell is made up of two half cells that are electrodes. One of these electrodes must have a higher electrode potential (higher tendency to lose electrons) than the other electrode

Complete step by step answer:
Let us discuss potential difference, the electrons flow from one electrode at higher potentials to an electrode to lower potential. Thus, the difference between the electrode potentials of two half cells is known as electromotive force (e.m.f) of the cell or the cell potential or voltage. It can also be defined as the force which causes the flow of electrons from one electrode to the other and thus, results in the flow of current.
Cell potential $=$ Sum of the half- cell potential
Cell potential $=$ Oxidation potential (anode) $+$ Reduction potential (cathode)
Cell potential $=$ O.P anode $-$ O.P cathode
Cell potential $=$ R.P cathode $-$ R.P anode
Or ${E_{cell}} = {E_{cathode}} - {E_{anode}}$
E.M.F of a cell is a measure of overall tendency which determines the spontaneity of a reaction to take place.
The concentration of $\left[ {O{H^ - }} \right]$ does not change with time in all the alkaline electrolytes batteries given in the question. So cell potential in all the alkaline electrolytes batteries given are independent of $\left[ {O{H^ - }} \right]$.

So, the correct answer is Option c.

Note: 1.The alkaline electrolyte is a 5 to 9 M concentrated aqueous solution of KOH (potassium hydroxide), NaOH ( sodium hydroxide), and LiOH (lithium hydroxide)
2.Alkaline electrolytes act as a mild acid electrolyte which gives them a better ionic conductivity than neutral electrolytes.
3.As the name says, the metal used in alkaline electrolytes is the alkaline elements of the periodic table.
4.Alkaline electrolytes have relatively high energy density and it is frequently used in small button cells.