- Daniell Cell Definition: A Daniell Cell is defined as an improved version of the Voltaic Cell that prevents polarization by converting chemical energy into electrical energy.
- Construction of Daniell Cell: The cell consists of a copper container with copper sulfate solution and a porous pot filled with diluted sulfuric acid containing a zinc rod.
- Oxidation and Reduction: Oxidation occurs at the zinc rod (cathode), forming zinc sulfate, while reduction occurs at the copper container (anode), depositing copper.
- Ion Movement: Hydrogen ions move through the porous pot to form sulfuric acid in the copper sulfate solution, facilitating continuous cell reactions.
- Avoiding Polarization: The Daniell Cell prevents hydrogen gas buildup on the anode by converting it into sulfuric acid, ensuring efficient operation.
A Daniell Cell is a modified version of the Voltaic Cell that solves its polarization problem. This improvement makes the Daniell Cell more efficient. The construction of a Daniell Cell is straightforward.
Construction of Daniell Cell
The Daniell Cell includes a copper container filled with concentrated copper sulfate solution. Inside this container, there is a porous pot filled with diluted sulfuric acid. An amalgamated zinc rod is placed in the diluted sulfuric acid. The sulfuric acid contains positive hydrogen ions and negative sulfate ions. When sulfate ions contact the zinc rod, they release electrons, creating zinc sulfate through an oxidation reaction. This makes the zinc rod negatively charged, acting as the cathode.
Positive hydrogen ions cross the porous pot’s wall and enter the copper sulfate solution, where they combine with sulfate ions to form sulfuric acid. Copper ions in the copper sulfate solution move to the inner wall of the copper container, gaining electrons through reduction and depositing as copper on the container’s wall.
Working of Daniell Cell
Let us explain the working principle of the cell step by step for better understanding.
In diluted sulfuric acid solution there are H+ and SO4– – ions.
The H+ ions come out to the copper sulfate solution through the wall of the porous pot. The sulfate ions of diluted sulfuric acid react with zinc rod where Zn++ ions get attached with SO4— ions and form zinc sulfate (ZnSO4). During this oxidation reaction, each zinc atom leaves two electrons in the zinc rod. Hence, the zinc rod becomes negatively charged that means it behaves as the cathode of the battery.
The hydrogen ions (H+) in the copper sulfate solution form sulfuric acid (H2SO4) and copper ions (Cu++) come to the wall of outer copper container.
Copper ions deposit on the copper container’s wall as copper metal by gaining electrons from the container. This process makes the copper container positively charged, meaning it acts as the anode. When we connect an external load between the zinc rod and the copper container wall, electrons flow from the zinc rod to the copper container.
In Daniell Cell, we can avoid the drawback of Polarization which is the main drawback of Voltaic Cell. As the hydrogen gas does not get deposited on the anode because it forms sulfuric acid before it reaches to the anode (copper container wall), there will be no layer of hydrogen formed on the anode to obstruct the reduction reaction.
