- No.4. Define a salt and give the characteristic properties of salts?
Answer. Salts are ionic compounds generally formed by the neutralization of an acid with a base. Salts are made up of positive ions (cations) and negative ions (anions). A cation is metallic ion and is derived from a base, therefore, it is called basic radical. While anion is derived from acid therefore it is called acidic radical.
Characteristic properties of salts
- Salts are ionic compounds found in crystalline form,
- They have high melting and toiling points.
(iii) Most of the salts contain water of crystallization which is responsible for the shape of the crystals. Numbers of molecules of water are specific for each salt and they are written with the chemical formula of a salt. For example,
Copper sulphate CuSO4.5H2O; Calcium sulphate CaSO4H2O
(iv) Salts are neutral compounds. Although, they do not compose of equal number of positive and negative ions, but have equal number of positive and negative charges.
- No.5. Explain with examples how soluble salts are prepared?
Answer. Soluble salts are often prepared in water. These can be prepared by different methods
(a) By the reaction of an acid and a metal: (Direct Displacement method)
This is direct displacement method in which hydrogen ion of acid is replaced by a reactive metal, i.e. calcium, magnesium, zinc and iron, e.g,
Acid + Metal ———> Salt + Hydrogen gas
2HCl(aq) + Mg(s)—————> MgCl2(aq) + H2(g)
(b) By the reaction of an acid and a base: (Neutralization method)
Iis a neutralization reaction in which acid and base react to produce a salts and water.
Acid + Base ———> Salt + Water
HCl(aq) + NaOH(aq) —————> NaCl(aq) + H2O(1)
(c) By the reaction of an acid and metallic oxide:
Mostly the insoluble metallic oxides react with dilute acids to form salt and water.
Acid + Metallic oxide ———> Salt + Water
H2SO4(aq) + CuO(aq) —————> CuSO4(aq) + H2O(aq)
(d) By the reaction of an acid and a carbonate
Dilute acids react with metallic carbonates to produce salts, water and carbon dioxide gas.
2HNO3(aq)+ Na2CO3(aq) —————> NaNO3(aq) + H2O + CO2(g)