Question

(a) Define efflorescence. Give examples.

Answer 1

Efflorescence is the property of some salts to lose wholly, or partly their water of crystallisation when their crystals are exposed to dry air even for a short time. Such substances are called efflorescent substances.

Examples:
Washing soda:
When washing soda is exposed to dry air, it becomes a monohydrate. That is,

$N{a}_{2}C{O}_3.10H_{2}O\underrightarrow{Dryair}N{a}_{2}C{O}_3.H_{2}O+9H_{2}O$

2. Epsom salt:
When Epsom salt is exposed to dry air, it becomes a monohydrate. That is,

$MgS{O}_4.7H_{2}O\underrightarrow{Dryair}MgS{O}_4.H_{2}O+6H_{2}O$