Question

(1). Write any two functions of the salt bridge.
(2). What is a cell constant? Write its S.I unit
(3). Write the Nernst equation for the cell reaction in the Daniel cell. How will ${E_{cell}}$ be affected when the concentration of $Z{n^{2 + }}$ ions is increased?

Answer 1

Hint: Chemistry is an interdisciplinary subject it has various branches and fields. One of the most important and widely used fields of chemistry is electrochemistry. Electrochemistry is the branch of chemistry that deals with the study of the relationship between electrical energy and chemical energy.

Complete answer:
(1). A salt bridge is a special type of device used in the electrochemical cells for the connection of the oxidizing chamber with the reduction chamber. A salt bridge usually has the concentration of strong electrolytes like silver nitrate $AgN{O_3}$ , potassium chloride $KCl$ , etc. The main functions of the salt bridge are as follows: - (i). It prevents the diffusion of one particular electrolyte to another. (ii). It also minimizes the liquid-liquid potential junction. (iii). It behaves like an electric contact between the two given half cells. (iv). It maintains the electrical neutrality of the two solutions. (v). It completes the cell.
(2). The definition of the cell constant is as follows: - It is the ratio between the electrode which is divided by the area of the cross-section of the electrode. In other words, it is the ratio of the distance between the conductance titration electrodes which is measured from the determined resistance of the solution having specific conductance. The S.I unit of cell constant is $c{m^{ - 1}}$ .
(3). The Nernst equation for the Daniel cell is as follows: -
$ Zn + C{u^{2 + }} \to Z{n^{2 + }} + Cu $
${E_{cell}} = {E^\circ }_{cell} - \dfrac{{0.059}}{2}\log \dfrac{{[Z{n^{2 + }}]}}{{[C{u^{2 + }}]}}$
As the concentration of $[Z{n^{2 + }}]$ increases the ${E_{cell}}$ decreases.

Note:
We have two main types of salt bridges namely: - (i) The glass tube bridge and (ii) The filter paper bridge. The reference for the calculation of the cell constant is the standard hydrogen having the value equals to zero. The Nernst equation has some constants in it like the gas constant temperature etc so on solving them we get $0.059$ .