One chemical that explicitly ignites with water is sodium hydrosulfite, which undergoes heating and spontaneous ignition when exposed to even a small amount of water (10% H2O). Additionally, other chemicals like sodium metal and sodium hydride react so vigorously with water that they can lead to ignition or explosions.
Understanding Water-Reactive Chemicals
Water-reactive chemicals are substances that react with water, often violently, to produce heat, flammable gases, or explosive mixtures. These reactions can be highly exothermic (releasing significant heat), leading to ignition of the evolved gases or surrounding materials.
Key Examples of Water-Reactive Chemicals and Their Reactions
Several chemicals demonstrate dangerous reactions upon contact with water, with some directly leading to ignition or creating conditions where ignition is highly probable.
| Chemical Name | Reaction with Water | Ignition Risk |
|---|---|---|
| Sodium hydride | Reacts explosively with water | High (explosions often involve rapid ignition) |
| Sodium hydrosulfite | Heating and spontaneous ignition with 10% H2O | Direct and Spontaneous Ignition |
| Sodium metal | Generates flammable hydrogen gas | High (flammable gas can ignite spontaneously) |
| Tetrachloro silane | Violent reaction | Potential (violent reactions can generate heat) |
Why Do These Reactions Cause Ignition?
The ignition observed with these chemicals is due to several factors:
- Exothermic Reactions: Many water-reactive chemicals undergo highly exothermic reactions with water, releasing enough heat to ignite the products of the reaction or nearby flammable materials.
- Generation of Flammable Gases: Chemicals like sodium metal react to produce hydrogen gas (H₂), which is highly flammable. The heat from the reaction can be sufficient to ignite this newly generated hydrogen.
- Spontaneous Combustion: In some cases, such as with sodium hydrosulfite, the reaction with water generates enough heat to cause the material itself to spontaneously combust.
- Explosive Decomposition: Reactions can be so rapid and energetic that they lead to an explosion, which inherently involves rapid combustion and ignition.
Safety Precautions
Due to their extreme reactivity, water-reactive chemicals require strict handling and storage protocols:
- Storage: Store these chemicals in tightly sealed containers in a dry, cool, and well-ventilated area, away from any potential sources of moisture or water.
- Handling: Always use appropriate personal protective equipment (PPE), including gloves, eye protection, and fire-resistant clothing. Handle small quantities to minimize risk.
- Firefighting: Water should never be used to extinguish fires involving these chemicals, as it would worsen the situation. Special dry powder extinguishers (Class D) are typically required.
[[Water Reactive Chemicals]]
