Page 90 - Chemistry ICSE Class X

76 ICSE Chemistry – 10

What are basic salts
The salt which contains one or more hydroxyl groups (coming from the
base) alongwith the anion coming from the acid is called a basic salt.
ƒ Some examples of basic salts are:
Pb(OH)Cl Lead hydroxychloride (Basic lead chloride)
CuCO .Cu(OH) 2 Basic copper carbonate (Malachite)
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Ca(OH)Cl Calcium hydroxychloride
ƒ Basic salts are obtained when the reaction between a base and acid is
carried out in almost neutral solution.
neutral
Ca(OH) (aq) + HCl(aq) o Ca(OH)Cl(aq) + H O
2
2
calcium hydroxide hydrochloric solution calcium hydroxy water

(base) acid (acid) chloride (basic salt)
What are double salts
dŚĞ ĂĚĚŝƟŽŶ ĐŽŵƉŽƵŶĚƐ ǁŚŝĐŚ ĞdžŝƐƚ ŽŶůLJ ŝŶ ƚŚĞ ƐŽůŝĚ ƐƚĂƚĞ ďƵƚ ĚŝƐƐŽĐŝĂƚĞ ŝŶƚŽ ƚŚĞŝƌ ĐŽŶƐƟƚƵĞŶƚ
ƐŝŵƉůĞ ŝŽŶƐ ǁŚĞŶ ĚŝƐƐŽůǀĞĚ ŝŶ ǁĂƚĞƌ ĂƌĞ ĐĂůůĞĚ ĚŽƵďůĞ ƐĂůƚƐ͘ ^ŽŵĞ ƚLJƉŝĐĂů ĚŽƵďůĞ ƐĂůƚƐ ĂƌĞ
͘
͘
͘
mohr’s salt ΀&Ğ^K ͘ ;E, Ϳ SO ϲ, K΁͕ potash alum ΀< SO Al ;^K Ϳ Ϯϰ, K΁ ĂŶĚ carnallite
2
4 2
4
2
4
2
4 3
2
4
+
΀< ů͘DŐ ů ͘ ϲ, O ͘ < ΁͘
2 2
Ö ŽƵďůĞ ƐĂůƚ ǁŚĞŶ ĚŝƐƐŽůǀĞĚ ŝŶ ǁĂƚĞƌ ďƌĞĂŬ ƵƉ ĐŽŵƉůĞƚĞůLJ ŝŶƚŽ ƚŚĞ ĐŽŶƐƟƚƵĞŶƚ ŝŽŶƐ͘
Ö dŚĞ ƐŽůƵƟŽŶ ŽĨ Ă ĚŽƵďůĞ ƐĂůƚ ŐŝǀĞƐ Ăůů ƚŚĞ ĐŚĞŵŝĐĂů ƚĞƐƚƐ ŽĨ ŝƚƐ ĐŽŶƐƟƚƵĞŶƚ ŝŽŶƐ͘ &Žƌ ĞdžĂŵƉůĞ͕
2+
+
ƚŚĞ ƐŽůƵƟŽŶ ŽĨ DŽŚƌ͛Ɛ ƐĂůƚ ŐŝǀĞƐ ƚŚĞ ƚĞƐƚƐ ĨŽƌ &Ğ ͕E, ĂŶĚ ^K 2– ŝŽŶƐ͘
4 4
What are mixed salts
dŚĞ ƐĂůƚƐ ǁŚŝĐŚ ĐŽŶƐŝƐƚ ŽĨ ŵŽƌĞ ƚŚĂŶ ŽŶĞ ĂĐŝĚ Žƌ ďĂƐŝĐ ƌĂĚŝĐĂů ;Žƌ ŵŽƌĞ ƚŚĂŶ ŽŶĞ ĂŶŝŽŶ Žƌ ĐĂƟŽŶͿ
+
–
ŽƚŚĞƌ ƚŚĂŶ , ĂŶĚ K, ĂƌĞ ĐĂůůĞĚ ŵŝdžĞĚ ƐĂůƚƐ͘ ^ŽŵĞ ƚLJƉŝĐĂů ŵŝdžĞĚ ƐĂůƚƐ ĂƌĞ ƐŽĚŝƵŵ ƉŽƚĂƐƐŝƵŵ
ĐĂƌďŽŶĂƚĞ ΀EĂ< K ΁ ĂŶĚ ĐĂůĐŝƵŵ ŽdžLJĐŚůŽƌŝĚĞ ΀ Ă;K ůͿ ů΁͘
3
What are complex salts
dŚĞ ĂĚĚŝƟŽŶ ĐŽŵƉŽƵŶĚ ĐŽŶƐŝƐƟŶŐ ŽĨ Ă ƐŝŵƉůĞ ŝŽŶ ĂŶĚ Ă ĐŽŵƉůĞdž ŝŽŶ ǁŚŝĐŚ ƌĞƚĂŝŶƐ ŝƚƐ ŝĚĞŶƟƚLJ ŝŶ
ƐŽůƵƟŽŶƐ ŝƐ ĐĂůůĞĚ Ă ĐŽŵƉůĞdž ƐĂůƚ͘
dŚƵƐ͕
Ž ŵ Ɖ ů Ğ dž Ɛ Ă ů ƚ U ^ŝŵƉůĞ ŝŽŶ н ŽŵƉůĞdž ŝŽŶ
< 4 ΀&Ğ; EͿ ΁ U ϰ < + н ΀&Ğ; EͿ ] 4–
ϲ
ϲ
ƉŽƚĂƐƐŝƵŵ ĨĞƌƌŽĐLJĂŶŝĚĞ ŝŽŶ
ŚĞdžĂĐLJĂŶŽĨĞƌƌĂƚĞ;//Ϳ
dŚĞ ĐŽŵƉůĞdž ŝŽŶ ŝƐ ƐŽ ƐƚĂďůĞ ƚŚĂƚ ŝƚ ĚŽĞƐ ŶŽƚ ŐŝǀĞ ƚĞƐƚƐ ĨŽƌ ŝƚƐ ĐŽŶƐƟƚƵĞŶƚ ŝŽŶƐ͘ &Žƌ ĞdžĂŵƉůĞ͕
–
2+
4–
΀&Ğ; EͿ ] ŝŽŶ ĚŽĞƐ ŶŽƚ ŐŝǀĞ ƚĞƐƚƐ ĨŽƌ &Ğ ĂŶĚ E ŝŽŶƐ͘
ϲ
General Properties of Salts
Some general properties of salts are described below:
^ĂůƚƐ ǁŚĞŶ ĚŝƐƐŽůǀĞĚ ŝŶ ǁĂƚĞƌ ;Žƌ ĂŶLJ
ŽƚŚĞƌ ƉŽůĂƌ ƐŽůǀĞŶƚͿ ĨŽƌŵ ĐŽŶĚƵĐƟŶŐ ƒ Physical state: Salts are nonvolatile crystalline solids.
ƐŽůƵƟŽŶƐ͘ ƒ Nature: Salts are electrovalent (or ionic) compounds. In solid state,
UCNVU FQ PQV EQPFWEV GNGEVTKEKV[ DGECWUG CNN VJG KQPU CTG ſZGF VQ VJGKT
sites in the lattice. In molten state or in solutions, the salts conduct
electricity because in molten salts/solutions the ions are free to move.
ƒ Solubility: Most salts are soluble in water. However, their degree
of solubility in water varies considerably from salt to salt. The
generalised solubility data are summarised as follows:
Š All salts of sodium, potassium and ammonium are soluble in
water.
Š All nitrates and nitrites are soluble in water.
Š All chlorides [except mercury(I) chloride (Hg Cl ), silver chloride
2
2
(AgCl) and lead chloride (PbCl )] are soluble in water.
2