Question

The phenomenon in which white transparent crystal changes into white powder is called:
A. Deliquescence
B. Efflorescence
C. Allotropy
D. Sublimation

Answer 1

Hint: The migration of a salt to the surface of a porous substance, where it forms a coating, is known as efflorescence in chemistry. The most important step entails dissolving an internally stored salt in water or, in rare occasions, another solvent.

Complete answer: Efflorescence occurs when a white clear crystal transforms into a white powder.
Efflorescences can be seen in both natural and man-made settings. It can occasionally suggest internal structural weakness (migration/degradation of component components) on porous construction materials, but it can also offer a cosmetic outside problem (primary efflorescence creating staining). As observed in the spalling of brick, efflorescence can block the pores of porous materials, causing internal water pressure to destroy the material.
So, the correct option is: (B) Efflorescence

Additional Information:
Efflorescence is further divided into two categories:
Primary efflorescence: Primary efflorescence occurs when making concrete contains too much water and occurs within the first 48 to 72 hour.
Prevention: Formulations containing liquid fatty acid combinations (e.g., oleic acid and linoleic acid) have been widely utilised to control primary efflorescence.
Secondary efflorescence: Secondary efflorescence occurs when water from the exterior (rain, condensation) penetrates the concrete and pulls the salts to the surface.
Prevention: Admixtures containing aqueous-based calcium stearate dispersion (CSD) are frequently added to the mix water at a later stage of the batching process to control secondary efflorescence.

Note:
Efflorescence isn't toxic or damaging in and of itself. It can lead to potential moisture issues, which can harm building materials structurally. When you observe efflorescence in your basement, on your paving stones, or on other structures, it's critical to act.