21.What is called oxidation reaction ?

          Any process which involves the addition of oxygen or any other electronegative radical or the removal of hydrogen is called oxidation.  It is the loss of electrons.

          eg:- Addition of oxygen

               carbon    oxygen                                carbon dioxide

          eg:- Removal of Hydrogen.

                 H₂S is oxidised by bromine(Br₂) to sulphur.

          eg:- loss of electron.

                 Cu (copper) is oxidised to Cu²⁺ (cupric ion)

                    Cu →        Cu²⁺  + 2e^-

                 (copper)     copper(II)ion

22.What is Reduction Reaction ?

          Any process involving the addition of hydrogen or any other electro positive radical or the removal of oxygen or any other electronegative radical is reduction.  Reduction is a process which involves the gain of electrons.

          eg:- Addition of hydrogen

                 Reaction between hydrogen sulphide and chlorine H_²S reacts with Cl₂ and gets oxidised to sulphur wheres.

                  Chlorine (Cl₂) gets reduced to HCl

23.What are the uses of acids ?

•  Citric acid is used to preserve food items.
•  Tartaric acid is used in backing powder.
• Boric acid is used as an eyewash.
• Acetic acid is used as vinegar.
• Hydrochloric acid is used as cleaning agent in toilet, pickle the metals.
• Nitric acid is used in the production of Ammonium nitrate.

24.What is a base ?

          A base is a compound which reacts with an acid to give salt and water only.  A base which is soluble in water is called an alkali.  When dissolved in water it gives hydroxide ion (OH).  (OH) is the only negatively charged ion.

25.On what are the basis are bases classified.?

          It is classified on the basis of strength, on the basis of concentration, on the basis of their acidity.

26.What is a strong alkali.?

          A base which dissociates almost completely  in an aqueous solution producing a high concentration of hydroxide ions is called a strong alkali.

          eg:- Sodium hydroxide (NaOH)

27.What is a weak alkali.?

          A base which dissociates partially in an aqueous solution to give a low percentage of hydroxide ions is called a weak alkali.

          eg:- Ammonium hydroxide (NH₄OH)

28.What are concentrated alkali.?

          Alkalies having relatively a high percentage of alkali in the aqueous solution are called concentrated alkali.

29.What are dilute alkali.?

          Alkali's having relatively a low percentage of alkali in their aqueous solutions are called dilute alkalies.

30.what is mono acidic alkali.?

          An Alkali that on complete dissociation in its aqueous solution produces only one hydroxide ion per molecule is called mono acidic alkali.

          eg:- Sodium hydroxide (NaOH) is a mono acidic alkali.