Question

EMF of Ni-Cd battery is dependent on the concentration of:
A. $Cd{\left( {OH} \right)_2}$
B. $Ni{\left( {OH} \right)_2}$
C. $O{H^ - }$
D. None of the these

Answer 1

Hint: We know that the electromotive force (e) or EMF which is the energy created by a cell or battery when per coulomb of charge is passing through it. EMF is measured in volts (V). Potential difference across the terminals of the cell when no current is flowing is equal to EMF.

Complete step by step answer:
A kind of rechargeable battery by nickel oxide hydroxide and metallic cadmium as electrodes is nickel-cadmium battery (or) Ni-Cd battery (or) NiCad Battery.
A completely-charged Ni-Cd cell has:
Nickel (III) oxide hydroxide positive electrode plate
Cadmium negative electrode plate
Separator
Alkaline electrolyte (potassium hydroxide)
During discharge, the chemical reactions that take place in the cadmium electrode are:
$Cd + 2O{H^ - } \to Cd{\left( {OH} \right)_2} + 2{e^ - }$
The chemical reactions that take place in the cadmium electrode are:
$2NiO\left( {OH} \right) + 2{H_2}O + 2{e^ - } \to 2Ni{\left( {OH} \right)_2} + 2O{H^ - }$
During discharge, the net redox reaction is,
$2NiO\left( {OH} \right) + Cd + 2{H_2}O \to 2Ni{\left( {OH} \right)_2} + Cd{\left( {OH} \right)_2}$
The reactions move from right to left during recharge. We have to know that alkaline electrolyte that is generally potassium hydroxide is not consumed in this reaction.
In this reaction, all species are present in solid. As all species are present in the solid, therefore, it does not contain any ionic concentration and the EMF will not be dependent on any species.
The maximum discharge rate for a Ni–Cd battery differs by size. Ni-Cd cells contain cell potential of 1.2 volts (V). Depending on the manufacturing of the cell, Ni-Cd batteries could be charged at several rates.

Therefore, the option D is correct.

Note:
We use specialty Ni-Cd batteries in cordless and wireless telephones, emergency lighting, and other applications. We can use Ni-Cd batteries as a substitute for primary cells. Aircraft starting batteries, electric vehicles, and standby power uses larger flooded cells.