Question

The higher the temperature of air, greater is the efflorescence. why?​

Answer 1

Answer:

The classical homogeneous nucleation theory was employed to calculate the efflorescence relative humidity (ERH) of airborne ammonium sulfate particles with a wide size range (8 nm to 17 microm) at room temperature. The theoretical predictions are in good agreement with the experimentally measured values. When the ammonium sulfate particle is decreased in size, the ERH first decreases, reaches a minimum around 30% for particle diameter equal to about 30 nm, and then increases. It is for the first time that the Kelvin effect is theoretically verified to substantially affect the ERH of ammonium sulfate particles smaller than 30 nm, while the aerosol size is the dominant factor affecting the efflorescent behavior of ammonium sulfate particles larger than 50 nm.

Answer 2

The higher the temperature of the air, the greater is the molecular activity, and thus greater is the efflorescence.

Explanation:

• Efflorescence is a process in which a spontaneous loss of water by a hydrated salt occurs when the aqueous vapor pressure of the hydrate is greater than the partial pressure of the water vapour in the air.
• For example, washing soda ($Na_{2} CO_{3}.10H_{2} O$) and Glauber’s salt ($Na_{2} SO_{4}.10H_{2} O$) lose all or part of their water of hydration (i.e. they effloresce), and their surfaces attain a powdery appearance.
• This is because the vapor pressure of washing soda and Glauber's salt is greater than the atmospheric vapor pressure.
• As the temperature increases, the molecular activity at the surface of the compound also increases.
• This increase in molecular activity results in a greater number of water molecules of a substance transitioning into gas molecules or vapor.
• With the increase in gas molecules, there is an increase in the aqueous vapor pressure.
• For example, In hydrated cupric sulfate, or blue vitriol ($CuSO_{4}.5H_{2}O$), even though the aqueous vapor pressure of the salt is relatively lower, it undergoes efflorescence in the presence of dry air (hot air).