Page 132 - Chemistry_Form_2

Chemistry
for Secondary Schools

Types of salts
Salts are categorised into neutral salts, acidic salts, and basic salts depending on
their pH values when dissolved in water. Salts can also be categorised as normal
salts, and double salts depending on their formation and compositions.
FOR ONLINE READING ONLY
Neutral salts
These are formed by the reactions of strong acids and strong bases. They are
called neutral salts because their aqueous solutions are neutral to litmus. Neutral
salts, when categorised based on formation and composition, are termed as
normal salts. A normal salt is formed by a complete replacement of replaceable
hydrogen atoms from an acid molecule by a metal. Examples of these salts are
NaCl, KCl, K SO 4 , KClO 3 , MgCl 2 , CuSO 4 , MgSO 4 , and NaNO 3 .
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Acidic salts
Acidic salts are those salts that produce acidic solutions when dissolved in water.
They are formed when a strong acid reacts with a weak base. Their aqueous
solutions turn blue litmus paper red. Acidic salts may contain one or more
replaceable hydrogen atom(s) present in an acid molecule or positive radical.
Examples of acidic salts include FeCl , ZnCl 2 , HgCl 2 , Fe 2 (SO 4 ) 3 , NaHSO 4 ,
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NaHPO , (NH 4 ) 2 SO 4 , and NH 4 Cl.
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Basic salts

Basic salts are a class of salts that produce alkaline solutions when dissolved in
water. Their aqueous solutions turn red litmus paper blue. A basic salt is a product
of a reaction between a strong base and a weak acid. Examples of basic salts
.
include CH COONa, Na 2 CO 3 , NaHCO 3 , and Na 2 C 2 O 4
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Double salts

A double salt is a mixture of two salts, which dissolves in water to give two
.
different cations or anions. Examples are potash alum, [KAl(SO 4 ) 2 12H 2 O],
.
.
ferric alum [NH 4 Fe(SO 4 ) 2 12H 2 O], and Mohr’s salt [(NH ) Fe(SO ) 6H O].
4 2
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4 2
Preparation of salts
There are several methods of preparing salts. The selection of the method to be
used depends on whether the salt required is soluble or insoluble in water.

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