Page 100 - Chemistry ICSE Class X

86 ICSE Chemistry – 10

ŽƉLJ ĂŶĚ ĐŽŵƉůĞƚĞ ƚŚĞ ĨŽůůŽǁŝŶŐ ƚĂďůĞ͗
Salt DĞƚŚŽĚ ŽĨ ƉƌĞƉĂƌĂƟŽŶ
ϭ͘ ŵŵŽŶŝƵŵ ƐƵůƉŚĂƚĞ ____________________
Ϯ͘ >ĞĂĚ ŶŝƚƌĂƚĞ ____________________
ϯ͘ ŝŶĐ ƐƵůƉŚĂƚĞ ____________________
ϰ͘ ĂůĐŝƵŵ ĐĂƌďŽŶĂƚĞ ____________________
ϱ͘ /ƌŽŶ;///Ϳ ĐŚůŽƌŝĚĞ ____________________
ϲ͘ ;ĂͿ tƌŝƚĞ ƚŚĞ ƚǁŽ ƐƚĞƉƐ͕ ǁŝƚŚ ďĂůĂŶĐĞĚ ĐŚĞŵŝĐĂů ĞƋƵĂƟŽŶƐ͕ ŝŶǀŽůǀĞĚ ŝŶ ƚŚĞ ƉƌĞƉĂƌĂƟŽŶ ŽĨ ůĞĂĚ ƐƵůƉŚĂƚĞ ĨƌŽŵ ůĞĂĚ
ĐĂƌďŽŶĂƚĞ͘
;ďͿ tŚLJ ŝƐ ƚŚĞ ĚŝƌĞĐƚ ĂĚĚŝƟŽŶ ŽĨ ƐƵůƉŚƵƌŝĐ ĂĐŝĚ ƚŽ ůĞĂĚ ĐĂƌďŽŶĂƚĞ ŶŽƚ ƌĞĐŽŵŵĞŶĚĞĚ ĨŽƌ ƚŚĞ ƉƌĞƉĂƌĂƟŽŶ ŽĨ ůĞĂĚ ƐƵůƉŚĂƚĞ͍

Hydrated Salts and Water of Crystallisation

What are the hydrated salts and water of crystallisation
6JG UCNVU YJKEJ EQPVCKP C FGſPKVG COQWPV QH YCVGT JGNF KP VJGKT NCVVKEG QT
^ĂůƚƐ ĐŽŶƚĂŝŶŝŶŐ ǁĂƚĞƌ ŽĨ
ĐƌLJƐƚĂůůŝƐĂƟŽŶ ĂƌĞ ĐĂůůĞĚ hydrated structure) are called hydrated salts.
salts. 6JG FGſPKVG PWODGT QH YCVGT OQNGEWNGU RGT OQNGEWNG QH VJG UCNV
present as bound water in its structure is called the water of crystallisation.
Some typical salts which contain water of crystallisation are listed in
Table 3.3.

Table 3.3 Some typical salts containing water of crystallisation
Hydrated salts Water of crystallisation
Common name in terms of the number of
Chemical name Formula Colour molecules of water

.
Blue vitriol Copper(II) sulphate CuSO 5H O Blue 5
2
4
.
Green vitriol Iron(II) sulphate FeSO 7H O Light green 7
4
2
Borax Sodium borate Na B O . 10H O White 10
2
7
2 4
.
Epsom salt Magnesium sulphate MgSO 7H O White 7
4
2
.
Washing soda Sodium carbonate Na CO 10H O White 10
2
2
3
.
Gypsum Calcium sulphate CaSO 2H O White 2
2
4
The water of crystallisation can be removed by heating but not always
without damaging the salt.
Efflorescence
What is meant by efflorescence
Certain hydrated salts when exposed to dry atmosphere at ordinary
temperature, lose their water of crystallisation and get transformed into
powder. Such salts are called GHƀQTGUEGPVU
The property by which a hydrated salt loses its water of crystallisation
when exposed to dry atmosphere is called GHƀQTGUEGPEG
6JG GHƀQTGUEGPEG KU HCXQWTGF D[
ƒ Higher atmospheric temperature
ƒ Dryness of the air
Examples: 5QOG GHƀQTGUEGPV UWDUVCPEGU CTG