Short Answer:
Reactive metals like sodium, potassium, and lithium are stored in kerosene because they react very easily with air (oxygen) and moisture. If left exposed, these metals can catch fire or explode due to their high reactivity.
Storing them in kerosene prevents contact with air and water, keeping them safe and stable. This practice ensures the metals maintain their chemical properties and can be handled safely in laboratories or industrial settings.
Detailed Explanation:
Storage of Reactive Metals
Reactive metals are highly active chemical elements that can easily undergo oxidation or react violently with water and air. Metals such as sodium (Na), potassium (K), lithium (Li), and calcium (Ca) are examples of such highly reactive metals. Their outermost electron is loosely bound, making them readily lose electrons and form positive ions. This high reactivity is the reason why they need special storage precautions.
Danger of Exposing Reactive Metals to Air
- Reaction with Oxygen: Most reactive metals form oxides when exposed to air.
- Example: 4Na + O₂ → 2Na₂O (Sodium reacts with oxygen).
- Potassium can ignite spontaneously in air due to rapid oxidation.
- Reaction with Moisture: Reactive metals also react with water vapor in the air to produce metal hydroxides and hydrogen gas, which is highly flammable.
- Example: 2K + 2H₂O → 2KOH + H₂
- Fire and Explosion Risk: The hydrogen gas released can catch fire, and vigorous reactions may lead to explosions. This makes handling reactive metals without protection extremely dangerous.
Why Kerosene is Used
- Inert Medium:
- Kerosene is a hydrocarbon liquid that does not react with metals.
- It forms a protective layer around the metal, preventing exposure to air and moisture.
- Prevents Oxidation and Hydrolysis:
- By immersing reactive metals in kerosene, they are kept away from oxygen and water.
- This prevents the metals from forming oxides, hydroxides, or other unwanted compounds.
- Safe Handling and Storage:
- Kerosene allows metals to be safely stored in laboratories and industries.
- When needed, the metal can be removed from kerosene for experiments or industrial processes.
Examples of Reactive Metals Stored in Kerosene
- Sodium (Na): Highly reactive with air and water; stored under kerosene to prevent ignition.
- Potassium (K): Reacts even more violently than sodium with water; kerosene prevents accidental fires.
- Lithium (Li): Reacts slowly with air but still stored in kerosene to maintain stability.
- Calcium (Ca): Stored in kerosene to prevent slow oxidation over time.
Laboratory Precautions
- Containers used for storing reactive metals are usually airtight and labeled clearly.
- Kerosene is chosen because it is readily available, inexpensive, and safe for this purpose.
- Gloves, tongs, and safety goggles are used when handling these metals, even under kerosene.
Industrial and Practical Importance
- Maintaining Metal Purity:
- Storing metals in kerosene ensures they remain pure and do not react before use.
- Safety in Transport:
- Reactive metals can be transported safely across laboratories and industrial plants when submerged in kerosene.
- Ease of Access:
- Metals stored in kerosene can be easily removed when required without the risk of unwanted reactions.
Summary
Reactive metals are highly unstable in air and moisture. Kerosene acts as an inert barrier, preventing oxidation and violent reactions. It allows safe storage, transport, and handling while maintaining the metal’s chemical properties. This is a simple, effective, and widely used method in chemistry laboratories and industries.
Conclusion:
Reactive metals are stored in kerosene because it prevents their contact with air and water, avoiding oxidation, formation of hydroxides, fire, or explosions. This method ensures safe handling, preserves the chemical stability of metals, and allows controlled use in experiments and industrial applications. The use of kerosene is essential for maintaining safety and metal purity.