Page 69 - Chemistry ICSE Class X

Study of Acids, Bases and Salts 57
Classification of Acids
zŽƵ ĂƌĞ ĂĚǀŝƐĞĚ ŶŽƚ ƚŽ ƚŽƵĐŚ ĂŶĚ
#EKFU ECP DG ENCUUKſGF KP OCP[ YC[U HQT GZCORNG CEKFU ECP DG ENCUUKſGF ƚĂƐƚĞ ĂŶLJ ĂĐŝĚ Žƌ ďĂƐĞ͘ dŚĞƐĞ
on the basis of ƐƵďƐƚĂŶĐĞƐ ŵĂLJ ŚĂƌŵ LJŽƵ͘
ͻ
ƒ Occurrence ƒ Strength ƌŽŶƐƚĞĚ ĂŶĚ >ŽǁƌLJ ĚĞĮŶĞĚ ĂĐŝĚ ĂƐ
ƒ Basicity ƒ Concentration ĂŶLJ ƐƵďƐƚĂŶĐĞ ǁŚŝĐŚ ŝƐ ĐĂƉĂďůĞ ŽĨ
+
ŐŝǀŝŶŐ ƵƉ Ă ŚLJĚƌŽŐĞŶ ŝŽŶ ;, Ϳ Žƌ ŝƐ Ă
How are acids classified on the basis of occurrence ƉƌŽƚŽŶ ĚŽŶŽƌ͘
ͻ
1P VJG DCUKU QH VJGKT QEEWTTGPEG CEKFU ECP DG ENCUUKſGF CU ,LJĚƌŽŐĞŶ ŝŽŶ ;, Ϳ ŝŶ ĂƋƵĞŽƵƐ
+
+
ƒ Naturally-occurring acids ƒ Mineral acids ƐŽůƵƟŽŶ ĞdžŝƐƚƐ ĂƐ , O ;ŵŽƌĞ
3
+
+
ƉƌĞĐŝƐĞůLJ ĂƐ , O Ϳ͘ , O ŝƐ ĐĂůůĞĚ
9 4 3
ŚLJĚƌŽŶŝƵŵ ŝŽŶ͘ &Žƌ ƚŚĞ ƐĂŬĞ ŽĨ
Naturally-occurring acids ĐŽŶǀĞŶŝĞŶĐĞ͕ , O ŝƐ ĂůƐŽ ĚĞƐĐƌŝďĞĚ
+
3
+
The naturally-occurring acids are weak acids. Many of our food items ĂƐ , ;aqͿ͘
contain weak acids in varying amounts.
The acids present in some common fruits and food items are described
below:
ƒ Citrus fruits, Onion Ascorbic acid (Vitamin C)
ƒ Grapes, Oranges, Lemons Citric acid
ƒ Cold drinks Carbonic acid
ƒ Apples Maleic acid
ƒ Curd Lactic acid
ƒ Tomatoes Oxalic acid >ĞŵŽŶƐ͕ ŽƌĂŶŐĞƐ͕ ƌĂǁͲŵĂŶŐŽĞƐ ĞƚĐ͕͘
ƒ Tamarind (imli) Tartaric acid ĂƌĞ ƐŽƵƌ ŝŶ ƚĂƐƚĞ ĚƵĞ ƚŽ ƚŚĞ ƉƌĞƐĞŶĐĞ
ŽĨ ĂĐŝĚƐ ŝŶ ƚŚĞŵ͘
ƒ Vinegar (sirka) Acetic acid

Mineral acids
Mineral acids are strong acids. Sulphuric acid (H SO ), hydrochloric acid DŽƐƚ ŵŝŶĞƌĂů ĂĐŝĚƐ ĂƌĞ ĐŽƌƌŽƐŝǀĞ ĂŶĚ
2
4
(HCl), nitric acid (HNO ) and phosphoric acid (H PO ) are some commonly ĐĂƵƐĞ ƐŬŝŶ ďƵƌŶƐ͘ dŚĞƌĞĨŽƌĞ͕ ƚŚĞƐĞ
4
3
3
used mineral acids. These acids are called mineral acids because these are ĂĐŝĚƐ͕ ƉĂƌƟĐƵůĂƌůLJ͕ ĐŽŶĐĞŶƚƌĂƚĞĚ
prepared from minerals. Mineral acids are very important from industrial ƐƵůƉŚƵƌŝĐ ĂĐŝĚ͕ ƐŚŽƵůĚ ďĞ ŚĂŶĚůĞĚ
point of view. These are used in the manufacture of fertilizers, industrial ǁŝƚŚ ĐĂƌĞ͘ dŚĞƐĞ ĂĐŝĚƐ ƐŚŽƵůĚ ŶĞǀĞƌ
ďĞ ƚŽƵĐŚĞĚͬƚĂƐƚĞĚ͘ /Ĩ ƌĞƋƵŝƌĞĚ͕ ƵƐĞ
chemicals, explosives, dyes, pigments, etc. ŽŶůLJ ǀĞƌLJ ĚŝůƵƚĞ ƐŽůƵƟŽŶƐ ŽĨ ƚŚĞƐĞ
One of the mineral acids, hydrochloric acid (HCl) present in our ĂĐŝĚƐ͘
stomach helps in the digestion of food.
How are acids classified on the basis of strength
1P VJG DCUKU QH VJGKT UVTGPIVJ CEKFU CTG ENCUUKſGF KPVQ VJG HQNNQYKPI VYQ
categories:
ƒ Strong acids ƒ Weak acids

Strong acids
The acids which are almost completely dissociated or ionised when
dissolved in water are called strong acids.
Hydrochloric acid (HCl), sulphuric acid (H SO ), nitric acid (HNO ),
2
3
4
perchloric acid (HClO ) are strong acids.
4
The solutions of strong acids in water are highly conducting due to dŚĞ ĚĞŐƌĞĞ ŽĨ ĚŝƐƐŽĐŝĂƟŽŶͬŝŽŶŝƐĂƟŽŶ
+
high concentration of hydrogen ion (H ) in the solution. ;DͿ ĨŽƌ ƐƚƌŽŶŐ ĂĐŝĚƐ ŝƐ ŐƌĞĂƚĞƌ ƚŚĂŶ
Ϭ͘ϯ Žƌ ϯϬй͘