Give the name of the process where fresh crystals of sodium carbonate,Na2CO3.10H2O become covered with white powder of formula Na2CO3.H2O
efflorescence.
The process you are referring to is known as efflorescence. Efflorescence occurs when a hydrated substance, such as sodium carbonate decahydrate (Na2CO3.10H2O), loses water molecules and forms a lower hydrate or anhydrous compound. In this case, the white powder that forms is sodium carbonate monohydrate (Na2CO3.H2O).
The process you are referring to is called efflorescence. Efflorescence occurs when a hydrated salt, in this case, sodium carbonate decahydrate (Na2CO3.10H2O), loses water of crystallization and forms a white powder of the anhydrous form, sodium carbonate monohydrate (Na2CO3.H2O).
To understand how this process occurs, let's break it down step by step:
1. Hydrated Salt: Sodium carbonate decahydrate (Na2CO3.10H2O) is a hydrated salt, meaning it contains water molecules within its crystal lattice. This form of sodium carbonate is often called soda ash or washing soda.
2. Environmental Factors: When exposed to a dry or low-humidity environment, the hydrated salt can lose its water molecules due to evaporation. This happens because the water molecules have a higher vapor pressure compared to the surrounding air.
3. Loss of Water: As the hydrated salt is exposed to the air, the water molecules begin to escape from the crystal lattice, resulting in the loss of water of crystallization. This process is known as dehydration.
4. Formation of Anhydrous Salt: Once the water molecules are lost, the crystal structure of the sodium carbonate decahydrate changes, and it transforms into the anhydrous form, sodium carbonate monohydrate (Na2CO3.H2O). This white powder is commonly referred to as soda ash monohydrate.
During the efflorescence process, the white powder of sodium carbonate monohydrate covers the surface of the original crystals, giving the appearance of a white powdery substance on the crystal surface.
It's important to note that efflorescence can also happen with other salts, not just sodium carbonate. The presence of efflorescence can be an indication of moisture or water infiltration in buildings, which can have implications for construction materials and structures.