By Sunil Bhardwaj

2841 Views

Construction: It is consist of PVC container. Anode is pure lead and the cathode is lead plate impregnated with PbO2. The electrolyte used is 20% H2SO4 of 1.75 sp.gr. When it is connected in the circuit the operation start.

Working:At L.H.E oxidation occures, $$Pb(s) + { SO }_{ 4 }^{ -2 } \longrightarrow Pb{ SO }_{ 4 }(s) + 2{ e }^{ - }$$ At R.H.E reduction occurs, $$Pb{ O }_{ 2 }(s) + 4{ H }^{ + } + { SO }_{ 4 }^{ -2 } + 2{ e }^{ - } \longrightarrow Pb{ SO }_{ 4 }(s) + 2{ H }_{ 2 }O$$ The Net Cell Reaction is combination of above two reactions, $$\boxed { Pb(s) + Pb{ O }_{ 2 }(s) + { H }_{ 2 }{ SO }_{ 4 } \longrightarrow 2Pb{ SO }_{ 4 }(s) + 2{ H }_{ 2 }O }$$ This reaction is while discharging, so for charging it will be reverse.

On applying the law of mass action to above cell reaction, $$K = \frac { { a }_{ Pb{ SO }_{ 4 }(s) }^{ 2 } \times { a }_{ { H }_{ 2 }O }^{ 2 } }{ { a }_{ Pb(s) } \times { a }_{ Pb{ O }_{ 2 }(s) } \times { a }_{ { H }_{ 2 }{ SO }_{ 4 } }^{ 2 } } = \frac { 1 }{ { a }_{ { H }_{ 2 }{ SO }_{ 4 } }^{ 2 } }$$ $$As \ { a }_{ Pb{ SO }_{ 4 }(s) } = 1, { a }_{ Pb(s) } = 1, { a }_{ Pb{ O }_{ 2 }(s) } = 1 \ and \ { a }_{ { H }_{ 2 }O } = 1,$$ On applying the Nernst expression for emf of the cell, $${ E }_{ cell } = { E }_{ cell }^{ 0 } - \frac { RT }{ nF } \ln { K }$$ $${ E }_{ cell } = { E }_{ cell }^{ 0 } - \frac { RT }{ 2F } \ln { \left( \frac { 1 }{ { a }_{ { H }_{ 2 }{ SO }_{ 4 } }^{ 2 } } \right) }$$ $${ E }_{ cell } = { E }_{ cell }^{ 0 } + 2\frac { RT }{ 2F } \ln { \left( { a }_{ { H }_{ 2 }{ SO }_{ 4 } } \right) }$$ $$\boxed { { E }_{ cell } = { E }_{ cell }^{ 0 } + \frac { RT }{ F } \ln { \left( { a }_{ { H }_{ 2 }{ SO }_{ 4 } } \right) } }$$ It is clear from the above equation that the emf of the cell depends on the activity of $${ H }_{ 2 }{ SO }_{ 4 }$$. The emf value for the cell is 2.0 to 2.1 volt.

Representation: $$\circleddash Pb,\ Pb{ SO }_{ 4 }(s)\ |\ \underset { 20\% }{ { H }_{ 2 }{ SO }_{ 4 } } \ |\ Pb{ SO }_{ 4 }(s),\ Pb{ O }_{ 2 }\ Pb\oplus$$

Uses:

(1) Used in automobiles, and Laboratory.

Demerits:

(1) It is costly.

(2) It is bulky,

(3) It is heavy,

(4) Care must be taken as H2SO4 is used.

#### Latest News

• Become an Instructor 4 March, 2018

Apply to join the passionate instructors who share their expertise and knowledge with the world. You'll collaborate with some of the industry's best producers, directors, and editors so that your content is presented in the best possible light..

#### More Chapters

• Spectroscopy
• Basic Quantum Chemistry
• Phase Rule
• Electrochemistry
• Colloidal State
• Chemical Thermodynamics
• Gaseous State
• Applied Electrochemistry
• Ionic Equilibria
• Nuclear Chemistry
• Solid State Chemistry
• Chemical Kinetics
• #### Other Subjects

• English
• Applied Physics
• Environmental Studies
• Physical Chemistry
• Analytical Chemistry
• Organic Chemistry
• Soft Skills
• Engineering Drawing
• General Medicine
• Mathematics
• Patente B Italia