Electrochemistry

Question 1

Explain the construction and working of silver-silver chloride electrode with a neat labelled diagram. Mention its advantages and applications.

Answer 1

——DIAGRAM——–

Construction:
It consists of a long glass tube at the bottom of which is placed agar gel which acts as a plug. The tube is filled with KCl soln whose conc might be 0.1M, 1M or saturated. The electrode potential of this system depends upon the conc of this KCl soln. To establish the electrical contact a silver wire coated with Agcl is used.

Working:
Electrode reaction:Agcl+e^-<=>Ag(s)+cl-
This electrode system when connected to other electrode system will undergo either the oxdn or redn rxn depending upon the other system to which it is connected.

Application:
1) It is used as a secondary reference electrode in place of a calomel or ion selective electrode.
2) Used to determine whether the potential difference is uniform or not in old pipelines.
3) Used as a portable reference electrode for measuring different depths of oil rigs and platforms.

Advantages:
1) It provides stable reference potential.
2) silver-silver chloride electrodes are easy to manufacture and handle.
3) it is suitable for various applications like measuring ph , potentiometric titration etc.

Question 2

Sketch a saturated calomel electrode. Write the electrode reaction and explain the working. Mention advantages and applications.

Answer 2

——–DIAGRAM———
Construction:
It consists of a long glass tube with the opening at the right hand side and an arm on the left hand side. At the bottom of the glass tube mercury (Hg) is placed which is then covered with mercury- mercurous chloride (Hg+Hg2Cl2) paste. The remaining glass tube is filled with kcl solution whose conc might be 0.1M, 1M or saturated. Depending on this conc we get electrode potential.
Standard calomel electrode= 0.2442V

Working:
Electrode reaction: Hg2Cl2+2e<=> 2Hg(l) + 2Cl-
This electrode system when connected to other electrode system will undergo either oxdn or redn rxn depending on the other electrode system to which it is connected.

Advantages:
1) it can be used in a wide range of aqueous solutions, which adds to their versatility.
2) It required minimal amount of maintenance, making them convinient for long term use.
3) stable reference potential.

Applications:
1) Calomel electrodes can be used in combination with a glass electrode for pH measurements. The potential difference between the calomel electrode and the glass electrode can be related to the pH of a solution.
2)Calomel electrodes are commonly used as reference electrodes in electrochemical cells and experiments.