Question

(i) Account for the following :
(a) White silver chloride trims grey in sunlight
(b) Brown coloured copper pmvder on heating in air turns into black coloured substance.
(ii) What do you mean by :
(a) Displacement reaction
(b) Reduction reaction
(c) Combination reaction ? Write balanced chemical equation.


CBSE Class X Science LA (5 Marks)

Answer 1

Answer:

(i)

(a) White Silver Chloride turns grey in the sunlight because of photochemical decomposition. In sunlight Silvel Chloride (AgCl₂) is decomposed into Silver (Ag) and Chlorine gas

2AgCl₂ → 2Ag + 2Cl₂

(b) Brown coloured Copper powder on heating in air turns into black coloured substance as Copper reacts with atmospheric Oxygen and forms Copper Oxide (CuO) which is black in colour. The reaction is gives as:

2Cu + O₂ → 2CuO

(ii)

(a) Displacement Reaction: Displacement reaction is a chemical reaction in which a more reactive element displaces a less reactive element from its compound. Example - Reaction of Iron with Copper Sulphate solution is an example of displacement reaction

Fe + CuSO₄ → Cu + FeSO₄

(b) Reduction Reaction : A chemical reaction where either Hydrogen is added to or Oxygen is removed from a compound. Example-

H₂ + F₂ → 2HF

(c) Combination Reaction: A reaction where two or more substances or compounds combine to form a single compound or product. Example-

C + O₂ → CO₂