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JAMB UTME - Chemistry - 2014

Question 1 Report

On exposure to the atmosphere, a hydrated salt loses its water of crystallization to become anhydrous. This phenomenon is referred to as
Answer Details
The phenomenon in which a hydrated salt loses its water of crystallization when exposed to the atmosphere is called efflorescence. Hydrated salts are those that have water molecules chemically bound to their crystal structures. When exposed to the atmosphere, the water molecules in the hydrated salt can evaporate into the air, leaving behind a dry, anhydrous salt. This process occurs due to the difference in vapor pressure between the water molecules in the salt and the water molecules in the air. If the vapor pressure of the water molecules in the air is lower than that of the water molecules in the salt, the water molecules in the salt will evaporate into the air. Efflorescence is commonly observed in certain salts such as sodium carbonate (Na2CO3), which is a hydrated salt containing ten water molecules. When exposed to air, Na2CO3 loses its water molecules and becomes anhydrous. The anhydrous form of Na2CO3 is commonly known as soda ash. Therefore, the correct answer is option A) efflorescence.
Read lesson note on Atomic Structure And Bonding (JAMB)
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