Question

(a) What are double displacement reactions ?
(b) Give an example of double displacement reaction,
where a gas is evolved.
(a) What is a decomposition reaction ?
(b) Decomposition reactions can occur by (i) heat
(ii) electricity and (iii) sunlight.
Give two balanced reactions for each.​

Answer 1

AnswEr:

a) In the Double Displacement Reaction, there is an exchange of two ionic compounds & makes two new compounds.

b) Example of Double Displacement Reaction is -

$\sf Na_{2}S + 2HCl \longrightarrow 2NaCl + H_{2}S$

c) Decomposition Reaction is a reaction in which an Single Substance breaks into two or more Substances.

d). Decomposition Reaction can occur by

1). Heat

$\sf ZnCO_{3} \longrightarrow ZnO + CO_{2}$

$\sf 2KClO_{3} + Heat \longrightarrow 2KCl + 3O_{2}$

$\rule{120}2$

2). Electricity

$\sf 2H_{2}O \longrightarrow 2H_{2} + O_{2}$

$\sf 2NaCl \longrightarrow 2Na + Cl_{2}$

$\rule{120}2$

3). Sunlight

$\sf 2AgCl_{2} + Sunlight \longrightarrow 2Ag +Cl_{2}$

$\sf H_{2} + Cl_{2} \longrightarrow 2HCl$

$\rule{120}2$

Answer 2

Answer:

Explanation:

(a) The reactions in which the different atoms or group of atoms are displaced by other atoms or other group of atoms, i.e two compounds change their ions and one of the product formed is insoluble, are said to be double displacement reactions.

(b) An example of double displacement reaction in which gas is evolved is Mg(s)  +  2HCl(aq)   ⟶   MgCl₂(aq)  +  H₂(g)

(a) In a decomposition reactions, a more reactive elements displaces a less reactive element from a compound.

(b)Decomposition reactions can occur by following reactions :-

• Heat - FeSO₄  ⟶  Fe₂O₃ + SO₂ + SO₃
• Electricity - 2H₂O  ⟶  H₂ + O₂
• Sunlight - 2Agbr  + Sunlight ⟶  2Ag + Br₂