Page 83 - Chemistry ICSE Class IX

Water 71
ƒ The solubility of sodium chloride in water increases slightly with a Compound ;20ΣCͿ Solubility*
rise in temperature. ĂůĐŝƵŵ ĐŚůŽƌŝĚĞ ϳϰ͘ϱ
ƒ The solubility of calcium sulphate slowly increases and then decreases WŽƚĂƐƐŝƵŵ ŶŝƚƌĂƚĞ ϯϮ͘Ϭ
with a rise in temperature. ^ŽĚŝƵŵ ĐŚůŽƌŝĚĞ ϯϲ͘Ϭ
ƒ The solubility of sodium sulphate in water increases up to 32.4°C and, WŽƚĂƐƐŝƵŵ ĐŚůŽƌŝĚĞ ϯϰ͘Ϭ
thereafter, decreases slightly. ^ŽĚŝƵŵ ŶŝƚƌĂƚĞ ϴϴ͘Ϭ
ŵŵŽŶŝƵŵ ĐŚůŽƌŝĚĞ ϭϬϵ͘Ϭ
What is solubility curve ΎŝŶ ŐƌĂŵƐ ƉĞƌ ϭϬϬ ŐƌĂŵƐ ŽĨ ǁĂƚĞƌ
The graph between the solubility of a substance and temperature is called
the solubility curve. The solubility curve describes the variation of solubility
of any substance with temperature.

What are the applications of the solubility curves
The solubility curves can be used for the following purposes:
ƒ To determine the trends in the solubility of any substance over a range
of temperature.
ƒ To determine the solubility of a substance at any temperature of
interest.
ƒ The conditions for the separation of a substance from a solution can be
worked out with the help of solubility curves.
ƒ The relative solubilities of various substances at any temperature can Fig. 3.10 Solubility curves for some
be determined. common substances

ASSIGNMENT 3

Solutions, Drinking water contains dissolved solids - their significance,
Air dissolved in water and its biological significance, Solubility, Solubility curves,
Effect of temperature and pressure on the solubility of gases and solids in liquids.

ϭ͘ EĂŵĞ ŽŶĞ ĞĂĐŚ ŽĨ ĂƋƵĞŽƵƐ ĂŶĚ ŶŽŶĂƋƵĞŽƵƐ ƐŽůƵƟŽŶƐ͘
Ϯ͘ tŚĂƚ ŝƐ ŵĞĂŶƚ ďLJ ŵĂƐƐ ƉĞƌ ĐĞŶƚ ŽĨ ƐŽůƵƚĞ ŝŶ ƚŚĞ ƐŽůƵƟŽŶ͍
ϯ͘ tŚĂƚ ŚĂƉƉĞŶƐ ǁŚĞŶ Ă ƐĂƚƵƌĂƚĞĚ ƐŽůƵƟŽŶ ŝƐ ĐŽŽůĞĚ͍
ϰ͘ EĂŵĞ ƚŚĞ ĨĂĐƚŽƌƐ ǁŚŝĐŚ ĂīĞĐƚ ƚŚĞ ƐŽůƵďŝůŝƚLJ ŽĨ Ă ƐƵďƐƚĂŶĐĞ ŝŶ Ă ůŝƋƵŝĚ͘
ϱ͘ ƌĂǁ Ă ƐŽůƵďŝůŝƚLJ ĐƵƌǀĞ ĨŽƌ Ă ƐƵďƐƚĂŶĐĞ ǁŚŝĐŚ ƐŚŽǁƐ ĂŶ ŝŶĐƌĞĂƐĞ ŝŶ ŝƚƐ ƐŽůƵďŝůŝƚLJ ǁŝƚŚ ƚĞŵƉĞƌĂƚƵƌĞ͘
ϲ͘ EĂŵĞ ƚŚĞ ƚǁŽ ŐĂƐĞƐ ŽĨ ďŝŽůŽŐŝĐĂů ƐŝŐŶŝĮĐĂŶĐĞ ǁŚŝĐŚ ƚŚĞ ĂƋƵĂƟĐ ƉůĂŶƚƐ ĂŶĚ ĂŶŝŵĂůƐ ŐĞƚ ĨƌŽŵ ǁĂƚĞƌ͘

Hydrated Substances

What are hydrated substances

ƒ The salts which contain a de nite amount of water held in their lattice
(or structure) are called hydrated salts/hydrated substances.
The water associated with the crystal (or molecule) of any salt is called
water of crystallisation.
The salts containing water of crystallisation are called hydrated salts.
Some typical salts which contain water of crystallisation (or are
hydrated salts) are:
ƒ Copper sulphate CuSO .5H O Blue
4
2
ƒ Iron sulphate FeSO .7H O Light green
4
2
ƒ Magnesium sulphate MgSO .7H O White
2
4
ƒ Sodium carbonate Na CO .10H O White
2
3
2
ƒ Calcium sulphate CaSO .2H O White
4
2