Electrochemistry is the branch of chemistry that deals with the conversion of chemical energy into electrical energy and electrical energy into chemical energy through oxidation-reduction (redox) reactions.
There are two types of electrochemical cells:
| Feature | Electrochemical (Galvanic/Voltaic) Cell | Electrolytic Cell |
|---|---|---|
| Energy conversion | Chemical energy → Electrical energy | Electrical energy → Chemical energy |
| Nature of reaction | Spontaneous | Non-spontaneous |
| External source | Not required | Required |
| Anode | Negative (−) | Positive (+) |
| Cathode | Positive (+) | Negative (−) |
| Universal Rule | Anode = always Oxidation | Cathode = always Reduction |
| Electron flow | Anode → Cathode | Power source → Electrodes |
| Example | Daniell Cell | Electrolysis of NaCl, CuSO₄ |
The Daniell cell is a common electrochemical cell that converts chemical energy into electrical energy.
A salt bridge is a U-shaped tube packed with an inert electrolyte — usually KCl, KNO₃, or NH₄NO₃ in agar gel.
Without it → charge builds up → reaction stops.
With it → ions flow in → charge balanced → reaction continues.
It connects the two half-cells and completes the electrical circuit.
As the Daniell cell runs, the anode beaker fills with excess Zn²⁺ and the cathode beaker fills with excess SO₄²⁻. The KCl in the salt bridge dissociates and fixes this:
The shorthand way to write an electrochemical cell — read it left to right:
For the Daniell Cell:
To measure electrode potentials, we compare every electrode to one universal reference — the SHE.
SHE (Reference) → 0.0 V — The baseline — neither oxidizes nor reduces
Zinc Anode (Zn²⁺ / Zn) → −0.76 V — Negative = strong tendency to oxidize ✦ loses electrons easily
Copper Cathode (Cu²⁺ / Cu) → +0.34 V — Positive = strong tendency to reduce ✦ gains electrons easily
📌 Remember: Higher the value → stronger oxidizing agent (takes electrons). Lower the value → stronger reducing agent (gives electrons).
The formula uses Standard Reduction Potentials:
(Note: The combined voltage of this standard Zn-Cu cell is 1.1V)
These original educational materials were created by Juber Aktar for JAtone. They are hosted on Google Drive or Google Slides for convenient access. Any future advertising will remain outside this file list and separate from the Preview and Download controls.
Electrochemistry: The Daniell Cell, Salt Bridge & SHE is a fundamental concept in physical chemistry. Understanding the mechanisms, reaction conditions, and stereo-chemical outcomes is crucial for mastering organic chemistry. Our curated resources provide step-by-step visualizations to help you excel.
SELF TEST
In an electrochemical (Galvanic) cell, what is the charge on the anode?
LEARNING SUPPORT
A Galvanic cell converts chemical energy into electrical energy through a spontaneous redox reaction. An Electrolytic cell does the reverse: it uses electrical energy to drive a non-spontaneous chemical reaction.
LOAN is a mnemonic to remember the properties of the left-side electrode in a Galvanic cell: L = Left side, O = Oxidation, A = Anode, N = Negative terminal.
The Copper rod acts as the cathode where reduction takes place. Cu²⁺ ions from the solution gain electrons and deposit as solid Copper metal onto the rod, causing it to become thicker over time.