Page 102 - Chemistry ICSE Class X

88 ICSE Chemistry – 10
Š Magnesium chloride (MgCl )
2
Š Zinc chloride (ZnCl )
2
Š Calcium chloride (CaCl )
2
Š Ferric chloride (FeCl )
3
Š Zinc nitrate [Zn(NO ) ]
3 2
Š Copper nitrate [Cu(NO ) ]
3 2
What are drying (or desiccating) agents
The substances which can remove moisture from other substances are
called drying agents (or desiccating agents).
All hygroscopic substances are drying (or desiccating) agents.

A desiccator is used for drying Examples:
moist substances ƒ Silica gel ƒ Phosphorus pentoxide (P O )
2
5
ƒ Quicklime (CaO) ƒ Magnesium perchlorate [Mg(ClO ) ]
4 2
ƒ Conc. sulphuric acid (H SO )
4
2
What are dehydrating agents
The substances which can remove water present in the structure of any
compound salt are called dehydrating agents.
Conc. sulphuric acid is a strong dehydrating agent. Conc. sulphuric
acid can remove water from copper sulphate pentahydrate, and also from
sugar molecule.
.
.
CuSO 5H O + H SO (conc.) o CuSO 4 + H SO 5H O
2
4
2
2
4
2
4
copper sulphate sulphuric acid copper sulphate
crystals (blue) (white)
C H O (s) + H SO (conc.) o 12C(s) + H SO . 11H O
4
2
2
2
12
22
11
4
Fig. 3.6 A drying tower sugar sulphuric acid carbon (charred)
ASSIGNMENT 8
Hydrated salts, Water of crystallisation, Efflorescence, Hygroscopic substances, Deliquescent substances
ϭ͘ ;ĂͿ tŚĂƚ ĂƌĞ ŚLJĚƌĂƚĞĚ ƐĂůƚƐ͍
;ďͿ EĂŵĞ ĨŽƵƌ ƐĂůƚƐ ǁŚŝĐŚ ĐŽŶƚĂŝŶ ǁĂƚĞƌ ŽĨ ĐƌLJƐƚĂůůŝƐĂƟŽŶ͘
;ĐͿ tƌŝƚĞ ƚŚĞ ĐŽůŽƵƌƐ ŽĨ ƚŚĞ ĨŽƵƌ ƐĂůƚƐ ŵĞŶƟŽŶĞĚ ŝŶ ;ďͿ͘
Ϯ͘ 'ŝǀĞŶ ďĞůŽǁ ŝƐ Ă ůŝƐƚ ŽĨ ƐŽŵĞ ƐĂůƚƐ͗
^ŽĚŝƵŵ ĐŚůŽƌŝĚĞ͕ ĂůĐŝƵŵ ĐŚůŽƌŝĚĞ ;ĂŶŚLJĚƌŽƵƐͿ͕ ŽƉƉĞƌ ƐƵůƉŚĂƚĞ ĐƌLJƐƚĂůƐ ;ĐŽƉƉĞƌ ƐƵůƉŚĂƚĞ ƉĞŶƚĂŚLJĚƌĂƚĞͿ
ŶƐǁĞƌ ƚŚĞ ĨŽůůŽǁŝŶŐ ƋƵĞƐƟŽŶƐ ƌĞůĂƚĞĚ ƚŽ ƚŚĞ ƐĂůƚƐ ŐŝǀĞŶ ŝŶ ƚŚĞ ůŝƐƚ͘
;ĂͿ tŚĂƚ ŝƐ ƚŚĞ ŶĂŵĞ ŐŝǀĞŶ ƚŽ ƚŚĞ ǁĂƚĞƌ ƉƌĞƐĞŶƚ ŝŶ ĐŽƉƉĞƌ ƐƵůƉŚĂƚĞ ĐƌLJƐƚĂůƐ͍
;ďͿ /Ĩ ĐŽƉƉĞƌ ƐƵůƉŚĂƚĞ ĐƌLJƐƚĂůƐ ĂƌĞ ŚĞĂƚĞĚ ƚŽ ŐĞƚ ĂŶŚLJĚƌŽƵƐ ĐŽƉƉĞƌ ƐƵůƉŚĂƚĞ͕
;ŝͿ tŚĂƚ ŝƐ ƚŚĞ ĐŽůŽƵƌ ŽĨ ƚŚĞ ĂŶŚLJĚƌŽƵƐ ĐŽƉƉĞƌ ƐƵůƉŚĂƚĞ͍
;ŝŝͿ ŽƵůĚ LJŽƵ ĚĞŚLJĚƌĂƚĞ ĐŽƉƉĞƌ ƐƵůƉŚĂƚĞ ƉĞŶƚĂŚLJĚƌĂƚĞ ďLJ ĂŶLJ ŽƚŚĞƌ ŵĞƚŚŽĚ ƚŚĂŶ ŚĞĂƟŶŐ͍
;ĐͿ tŚŝĐŚ ŽĨ ƚŚĞ ƐĂůƚƐ ŐŝǀĞŶ ŝŶ ƚŚĞ ůŝƐƚ ŝƐ ĚĞůŝƋƵĞƐĐĞŶƚ͍
ϯ͘ tŚLJ ŝƐ ĂŶŚLJĚƌŽƵƐ ĐĂůĐŝƵŵ ĐŚůŽƌŝĚĞ ƵƐĞĚ ŝŶ Ă ĚĞƐŝĐĐĂƚŽƌ͍
ϰ͘ EĂŵĞ ƚŚĞ ĨŽůůŽǁŝŶŐ͗
;ĂͿ Ŷ ĞŋŽƌĞƐĐĞŶƚ ƐƵďƐƚĂŶĐĞ͘ ;ďͿ ŚLJŐƌŽƐĐŽƉŝĐ ƐƵďƐƚĂŶĐĞ͘
;ĐͿ ĚƌLJŝŶŐ ĂŐĞŶƚ͘ ;ĚͿ ĚĞŚLJĚƌĂƟŶŐ ĂŐĞŶƚ͘