Glitter and Beauty
Classification of Elements
Introduction
- Electrochemistry is the branch of chemistry which deals with interconversion of chemical and electrical energy.
- Chemical energy is converted to electrical energy due to the chemical reaction in dry cell. Electrochemistry is useful to design and operate such cells.
- The current research focusses on designing fuel cells as compact source of electricity.
The word electrolysis is made up of two words electro, which means the flow of electrons, and lysis, which means pertaining to.
Electrolysis is the process by which a chemical compound in the fused state or in aqueous solution undergoes a chemical change on the passage of current.
During electrolysis, a chemical change is brought about by electric energy.
- Electrolytic cell or voltameter is the vessel consisting of glass, containing two electrodes and an electrolyte.
- The graphite or metal rods through which electric current enters or leaves from an electrolyte are called electrodes.
Therefore, a cathode is the electrode which is connected to the negative terminal of the battery. It has an excess of electrons. An anode is than electrode which is connected to positive terminal of battery. It has deficiency of electrons.
Difference between cathode and anode
| Anode | Cathode |
| Connected to positive terminal of the battery | Connected to negative terminal of the battery |
| Migration of anion occurs | Migration of cations occurs |
| Oxidation occurs | Reduction occurs |
Differences between metallic and electrolytic conductors
| Metallic Conductors | Electrolytic Conductors |
| Flow electrons from negative pole to positive pole is responsible for conduction. | Flow of ions in solution to the respective electrodes is responsible for conduction. |
| Shown by metals and alloys | Shown by aqueous solution of ionic compounds |
| Present in both solid and liquid state of metals | Present in molten or aqueous solution of the ionic compounds |
| Physical process | Chemical process |
- Electrolyte refers to the compound, which in fused state or in aqueous state conducts electric current so that chemical decomposition of the compound takes place.
The electrolytes which allow a large amount of current to flow through them are called strong electrolytes. The strong electrolytes in fused state are completely dissociated and hence, their ions are free to move in any direction.
Examples include an aqueous solution of mineral acid and caustic alkalis.
The electrolytes which allow a very small amount of current to flow through them are called weak electrolytes. The strong electrolytes in fused state are completely dissociated. Hence, their ions are free to move in any direction.
Examples include aqueous solution of acid and bases.
- Non-electrolyte is the chemical compound which does not conduct electric current in fused state or in aqueous solution and does not undergo any chemical decomposition.
Examples are carbon tetrachloride, alcohol, ether, pure water, etc.
Differences between strong and weak electrolytes
| Strong electrolytes | Weak electrolytes |
| Allows large amount of electricity to flow through them | Allows small amount of electricity to flow through them |
| Good conductors | Poor conductors |
| Undergo complete dissociation in molten or aqueous solution | Undergo partial dissociation in molten or aqueous solution |
| Contain free mobile ions | Contains ions and molecules |
| Examples are HCl, H2SO4, HNO3, NaOH, KOH, NaCl, CuSO4, etc. | Examples are H2CO3, CH3COOH, HOOC-COOH, NH4OH, Ca(OH)2, (NH4)2CO3, Pb(CH3COO)2 |
- Ions
When a chemical compound in fused state or in aqueous solution breaks up into electrically charged atoms or group of atoms, the charged particles are called ions. A positively charged ion is cation. They migrate towards cathode. A negatively charged ion is an anion. They migrate towards anode.
Differences between cation and anion
| Cation | Anion |
| Positively charged | Negatively charged |
| Migrate to cathode | Migrate to anode |
| Get reduced to form neutral atom | Get oxidised to form neutral atom |
| Examples, Na+, Al3+ | Examples, Cl− , OH− |
Mechanism of electrolysis
It was put forward by Avante Arrhenius, a Swedish chemist. Following are the points given in his theory of electrolytic dissociation.
- An electrolyte is a substance which in an aqueous solution breaks into positively charged cations and negatively charged anions.
- The movement of ions within the electrolyte is responsible for the flow of electric current.
- The degree of dissociation refers to the extent to which electrolyte dissociates into ions.
- Cations and anions unite to form neutral ion, setting up equilibrium.
- An electrolyte is electrically neutral.
Electrolysis of water:
Add a small amount of salt to water and pour this solution into a beaker. Connect two electrical wires to the terminal of the battery as shown in the figure. The two ends of the wires will serve as electrodes when the insul…
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