Name: Faraday’s Second Law of Electrolysis
Uploaded: 2019-07-19
Duration: 3 min 37 s
Description: Faraday’s second law of electrolysis establishes the relationship between a definite amount of electricity passed and the number of products formed in differ...

Question

State and explain Faraday's law of electrolysis. Calculate the value of current required to deposit

0.972 g

of chromium in

3

hours. E.C.E of chromium

= 0.00018 g C^{- 1}

.

Accepted Answer

Faraday's law of electrolysis $:$

$(i)$ The mass of any substance $(m)$ liberated at an electrode during electrolysis is proportional to the quantity of charge $= 0.00018 g C^{- 1}$ that passes through the electrolyte during that period.

$m \propto q$ or $m = Z q$

where $Z$ is constant of proportionality known as electrochemical equivalent and depends on the nature of the substance that is liberated.

$(ii)$ When the same quantity of charge is passed through different electrolytes, the mass of different substances liberated at the respective electrodes is directly proportional to chemical equivalents $(c)$ .

$m \propto c$ or $\frac{m_{1}}{m_{2}} = \frac{c_{1}}{c_{2}}$

From these two laws of electrolysis, depending upon the stoichiometry of the electrode reaction, amount of current can be deduced for oxidation-reduction reaction.

As the ratio of $\frac{c}{Z}$ is a constant called Faraday constant which is defined as the amount of charge capable of liberating or dissolving $1$ kilomole of monovalent substance during electrolysis and comes out to be $96500 C {mol}^{- 1}$ . Since one mole contains Avogadro's Number of molecules or ions or atoms,

$∴ F = N_{A} e$

This confirms atomicity in electricity.

Given,

Mass of chromium to be deposited $m = 0.972 g$

Time for deposition $t = 3 h = 3 \times 3600 = 10800 s$

E.C.E of chromium $Z_{C r} = 0.00018 g C^{- 1}$

Let $I$ be the current required for given deposition.

$∵ m = Z q = Z I t$

$\Rightarrow I = \frac{m}{Z_{C r} t} = \frac{0.972}{0.00018 \times 10800} = 0.5 A$

So, the required current is $0.5 A$ .

Odisha Board Solutions for Chapter: Thermal And Chemical Effects of Electric Current, Exercise 1: MODEL QUESTIONS

Odisha Board Physics Solutions for Exercise - Odisha Board Solutions for Chapter: Thermal And Chemical Effects of Electric Current, Exercise 1: MODEL QUESTIONS

Questions from Odisha Board Solutions for Chapter: Thermal And Chemical Effects of Electric Current, Exercise 1: MODEL QUESTIONS with Hints & Solutions

Learn and Prepare for any exam you want !