Page 71 - Chemistry ICSE Class X

Study of Acids, Bases and Salts 59
Š Tribasic acids form two acid salts and one normal salt. For example,
3
the various salts of phosphoric acid are, Solid : ŽƌŝĐ ĂĐŝĚ ;, BO Ϳ 3 4
3
Liquid : WŚŽƐƉŚŽƌŝĐ ĂĐŝĚ ;, WK Ϳ ĂƌĞ
Normal salt: Na PO 4 (Sodium phosphate) ƚLJƉŝĐĂů tribasic ĂĐŝĚƐ͘
3
Acid salts: NaH PO (Sodium dihydrogen phosphate)
4
2
Na HPO (Sodium trihydrogen phosphate)
2
4
How are acids classified on the basis of concentration
All acids are the solutions of acidic gases in water. On the basis of
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categories.
ƒ Concentrated acids. A solution that contains the maximum amount of
the acidic gas in it is called concentrated acid.
ƒ Dilute acids. A solution containing lesser amount of the acidic gas
(i.e., larger amount of water) is called dilute acid. The degree of
dilution may be mentioned as moderately dilute, dilute, very dilute
or very-very dilute acid.
In practice, dilute acid is prepared by adding the required amount of
concentrated acid into a calculated amount of water.

Why is the concentrated acid added into water and not

water to the acid while preparing a dilute solution of
an acid from concentrated acid
Dissolution of a concentrated acid or a base, particularly concentrated ĐŝĚ ƐŽůƵƟŽŶƐ ŽĨ ĚŝīĞƌĞŶƚ
sulphuric acid and solid sodium hydroxide, is a highly exothermic reaction. ĐŽŶĐĞŶƚƌĂƟŽŶƐ ĐĂŶ ďĞ ƉƌĞƉĂƌĞĚ ďLJ
ĐŚĂŶŐŝŶŐ ƚŚĞ ƌĞůĂƟǀĞ ĂŵŽƵŶƚƐ ŽĨ ƚŚĞ
When water is added to a concentrated acid, the heat liberated is so ĂĐŝĚŝĐ ŐĂƐ ĂŶĚ ǁĂƚĞƌ͘
large that the solution starts almost boiling. This may cause spurting of the
hot acid solution and harm the person. Excessive heating may even break
the glass container.
That is why, concentrated acids and bases are diluted by slowly adding
concentrated acid or base into water with constant stirring.

ASSIGNMENT 1

Acids, Characteristics of acids, Classification of acids

ϭ͘ ,Žǁ ǁŽƵůĚ LJŽƵ ƐŚŽǁ ƚŚĂƚ ƚŚĞ ŐŝǀĞŶ ůŝƋƵŝĚ ŝƐ ĂĐŝĚŝĐ ŝŶ ŶĂƚƵƌĞ͍
Ϯ͘ tƌŝƚĞ ƚŚĞ ĨŽƌŵƵůĂ ŽĨ ƚŚĞ ŝŽŶ ƉƌŽĚƵĐĞĚ ďLJ Ăůů ĂĐŝĚƐ ǁŚĞŶ ĚŝƐƐŽůǀĞĚ ŝŶ ǁĂƚĞƌ͘
ϯ͘ EĂŵĞ ƚǁŽ ĞĂĐŚ ŽĨ ƚŚĞ ĨŽůůŽǁŝŶŐ͗
;ĂͿ EĂƚƵƌĂůůLJͲŽĐĐƵƌƌŝŶŐ ĂĐŝĚƐ
;ďͿ DŝŶĞƌĂů ĂĐŝĚƐ
;ĐͿ ^ƚƌŽŶŐ ĂĐŝĚƐ ĂŶĚ ǁĞĂŬ ĂĐŝĚƐ
;ĚͿ ŝďĂƐŝĐ ĂĐŝĚƐ
ϰ͘ EĂŵĞ ƚŚĞ ŝŽŶ ƚŚĂƚ ƚƵƌŶƐപ;ĂͿ ďůƵĞ ůŝƚŵƵƐ ƌĞĚപ;ďͿ ƌĞĚ ůŝƚŵƵƐ ďůƵĞ
ϱ͘ 'ŝǀĞ ƚŚĞ ŶĂŵĞ ĂŶĚ ĨŽƌŵƵůĂĞ ŽĨ ŶŽƌŵĂů ĂŶĚ ĂĐŝĚ ƐĂůƚ ŽĨ ƐƵůƉŚƵƌŝĐ ĂĐŝĚ͘
ϲ͘ ;ĂͿ ĞĮŶĞ ďĂƐŝĐŝƚLJ ŽĨ ĂŶ ĂĐŝĚ͘
;ďͿ tŚĂƚ ŝƐ ƚŚĞ ďĂƐŝĐŝƚLJ ŽĨ
;ŝͿ ŶŝƚƌŝĐ ĂĐŝĚ ;ŝŝͿ ŽdžĂůŝĐ ĂĐŝĚ ;ŝŝŝͿ ƉŚŽƐƉŚŽƌŝĐ ĂĐŝĚ͍