Question

The unit of electrochemical equivalent is:
A. Gram
B. Gram/ampere
C. Gram/coulomb
D. Coulomb/gram

Answer 1

The mass of the element deposited or liberated at any electrode is directly proportional to the amount of charge passed. (i.e, one coulomb of electricity). The proportionality can be made into an equality by, z the proportionality constant known as the electrochemical equivalent of a substance.

Complete step by step answer:
The above explained proportionality is the first law of faraday's laws of electrolysis. It explains the quantitative aspects of electrolysis. Therefore we can write the mathematical formulation of the first law which would be,
W=zq( it defines the mass of the substance in grams deposited or liberated by passing one coulomb charge)
Let us understand the concept of electrochemical equivalent from the second law as well it states that The electrochemical equivalent of a substance is equal to the mass of a substance deposited at an electrode on passing a certain amount of charge. If the electrochemical equivalent of metal is 1 gram/coulomb, then we can conclude that 1 equivalent weight of an equivalent of e- has 96500 Coulomb charge.
Since 96500 coulomb of electricity discharges 1 gram equivalent mass of any element (E), one coulomb of electricity would discharge E/96500 g of the element. By combining first and second law we get,
$Z = \dfrac{E}{{96500}}g/c$
The electrochemical equivalent of a material depends on the nature of the material.
In a cell the chemical energy is converted to electrical energy, the weight of electrons are in grams. if one charge will transfer one gram based on this we can express the unit of electrochemical equivalent. So the electrochemical equivalent is gram/coulomb.

Hence the option C is correct.

Note:
It should be made clear that cathode is the electrode at which reduction reaction occurs while the anode is the electrode where the oxidation occurs. Do not relate the sign of the electrode with the nature of the electrode.