Preparation And Properties Of Acids

Physical Properties of acids
i)  All the acids are colourless, though sulphuric acid may be brown at times due to impurities.
ii) Acid taste sour.
iii) Acid turn blue litmus red and methyl orange pink.
iv) Acids are corrosive. They cause blisters on skin. And eat up materials like cloth, wood, metal structures and stone works. Acids never stored in metal containers because they gradually corrode and eat up the metal container.
v) Sulphuric acid is oily and heavier than water.
vi) Dilute acidic solutions are good conductors of electricity.
vii) All mineral acids are not corrosive. Carbonic acid is used in making soft drinks.
viii) Most acids are soluble in water

Chemical Properties of acids
1. Action with metals:
Metals displace hydrogen from the acids. They release hydrogen gas.
     \( Zn + HCl \to ZnCl_2 + H_2 \uparrow \)       
            
       \( Zn + H_2 SO_4 \to ZnSO_4 + H_2 \uparrow \)     
      
      \( Mg + 2HNO_3 \to Mg(NO_3 )_2 + H_2 \uparrow \)
       
Hydrogen gas is not evolved when dilute nitric acid is mixed wit zinc. The action of nitric acid with metals depends upon various physical factors.’ Hydrogen gas is released when any metal react with acids under certain conditions.

2. Action with metal oxides:
All dilute mineral acids react with all metallic oxides to form their respective metallic salts and water.

       \( CaO + 2HNO_3 \to Ca(NO_3 )_2 + H_2 O \)
        Calcium oxide + nitric acid \( \to \) Calcium nitrate+water

        \( ZnO + 2HCl \to ZnCl_2 + H_2 O \)
        Zinc oxide + Hydrochloric acid \( \to \) Zinc chloride+water
 

3. Action of metallic hydroxides:
All dilute mineral acids react with all metallic hydroxides to form their respective metallic salts and water only.

         \( 2NaOH + H_2 SO_4 \to Na_2 SO_4 + 2H_2 O \)
        Sodium oxide + sulphuric acid \( \to \)  Sodium Sulphate+water

         \( Ca(OH)_2 + H_2 SO_4 \to CaSO_4 + 2H_2 O \)   
        Calcium Hydroxide + Sulphuric acid \(\to \) Calcium Sulphate+water

4. Action with metallic carbonates:
All dilute mineral acids react with metallic carbonates to form their respective metallic salts, carbon dioxide and water.

         \( MgCO_3 + H_2 SO_4 \to MgSO_4 + CO_2 + H_2 O \)   
        Magnesium carbonate + Sulphuric acid \(\to \) Magnesium sulphate+water

         \( ZnCO_3 + 2HCl \to ZnCL_2 + CO_2 + H_2 O \)   
        Zinc carbonate + Hydrochloric acid \(\to \) Zinc chloride+water

Hydro acids:
An acid which contains hydrogen and a non-metallic element, other than oxygen is called Hydroacid.
 Ex:    HCl, HBr, HI, HF, HCN and H₂S

Oxyacids:
An acid which contains oxygen, along with hydrogen and one more element is called oxyacids.
 Ex: HNO₃, HNO₂, H₂SO₄, H₂SO₃, H₃PO₄, H₂CO₃, HCOOH, CH₃COOH and \( \mathop C\limits_{\mathop |\limits_{COOH} } OOH \)  
Solid State Acids:
H₃PO₄, H₃BO₃, \( \mathop C\limits_{\mathop |\limits_{COOH} } OOH \)

Liquid State Acids:
        HCl, H₂SO₄, HNO₃, CH₃COOH, HCOOH