Electrochemistry And Cells

How does a cell in a T.V remote make it work or how a battery of mobile phone charges when connected to its charger? All such questions are answered in the branch of science known as electrochemistry. Electrochemistry is the study of producing electricity through chemical reactions and also the use of electricity to carry out non-spontaneous chemical reactions. To achieve the above-mentioned aim cells are used. Cells are devices in which chemical reactions due to electricity or produces electricity. 

There Are Two Types of Cells

  • Electrochemical cells

  • Electrolytic cells

Electrochemical Cells

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These cells are those cells that produce electricity through chemical reactions. These cells are also known as Voltaic cells or Galvanic cells. Chemical energy is converted into electrical energy by the cells.

An example of an electrochemical cell is the Daniell cell.

Electrolytic Cells

These cells are those cells which use electricity to carry out non-spontaneous chemical reactions. So it's clear that these cells convert electrical energy into chemical energy.

The basic difference between electrochemical cells and electrolytic cells are listed in the table below:

Difference Between Electrochemical Cells And Electrolytic Cells

Electrochemical Cell/Galvanic cell

Electrolytic Cell

The anode is negative, the cathode is positive

The anode is positive, the cathode is negative

Electrons flow from anode  to cathode

Electrons flow from anode to cathode

A Typical Cell Structure

A cell has two electrodes-cathode (positive terminal) and anode (negative electrode). Both the electrodes are dipped in their respective metal salt solutions. In the case of electrochemical cell Anode is oxidation half cell and the cathode is known as reduction half cell according to the chemical reaction taking place at them. A Salt bridge is a U shape tube containing a gel permeated with an electrolyte, connecting the two electrodes. 

What Is A Daniell Cell?

A Daniell Cell is an electrochemical cell which carries out chemical reactions to produce electricity. In the Daniell cell, Zinc metal is made of the anode, and copper metal is the cathode. The zinc anode is dipped in Zinc salt solution and the Copper cathode is dipped in the copper salt solution. At the anode, oxidation takes place and solid zinc converts into zinc ions. At the cathode, copper ions get reduced to copper metal and get deposited. 

The Daniell cell has a voltage of 1.1v.

Daniell Cell Chemical Reaction

Zn(s) + Cu+2(aq) -------> Zn+2(aq) + Cu(s)

The above reaction can be split into two as follows-

Anode reaction /oxidation half cell reaction

Zn(s)-------> Zn+2 + 2 e-

2 electrons are released and zinc metal is oxidized.

Cathode reaction/ reduction half cell reaction

Cu+2 + 2 e- ---------> Cu (s)

Copper ions are reduced to copper metal.

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Daniell Cell Working

As we have seen above, the setup of the Daniell cell and the cell reactions taking place in the Daniell cell now we can understand the working of Daniell cells. The zinc metal oxidizes at the anode and 2 electrons are released. These electrons travel from anode to cathode through a metal wire that connects both the electrodes. This flow of free electrons produces electricity in the direction opposite to the flow of electrons that is from cathode to anode. Salt bridge completes the circuit.

Daniell Cell Representation

Zn | Zn+2(aq) || Cu+2(aq) | Cu

The symbol double vertical lines || represents the salt bridge. The left part is oxidation half cell and the right part is reduction half cell.

Applications of Daniell Cell

Daniell cells are used to generate electricity or to store electric energy. Daniell cells are used in battery development and electrical telegraphy. Battery refers to a group of cells combined.

FAQs (Frequently Asked Questions)

1. Explain the working of the Daniell cell when an external voltage is applied.

The Daniell cell voltage is 1.1 voltage. If the external voltage of different values is applied then the Daniell cell works differently. This is explained below.

Working of Daniell cell when an external voltage is applied -

  • When an external voltage of less than 1.1 v is applied then the cell keeps working till the voltage reaches 1.1v.

  • When the external voltage of greater than 1.1v is applied then the electrons start to flow from cathode to anode and current starts to flow from anode to cathode. Zinc metal starts to deposit at the anode.

  • When an external voltage is equal to 1.1v then no flow of current or electrons takes place.

2. How does an electrolytic cell work?

Electrolytic cells are just the reverse of an electrochemical cell. In the electrolytic cell, the positive terminal is Anode and the Negative terminal is the cathode. In this oxidation takes place at the anode and reduction takes place at the cathode. Electrons move from the anode towards the cathode. Electrons are forced through the circuit through an external source. This is because external electricity is used to carry out a non-spontaneous reaction. This converts electrical energy into chemical energy. 

Irrespective of whether it is a galvanic cell or electrolytic cell oxidation always takes place at the anode and reduction takes place at the cathode.