Double displacement reaction takes place with:
i) Precipitates are formed.
ii) Evolution of a gas
iii) Change in colour.

Correct option is B

Correct Answer: B) i, ii and iii

Explanation:

A double displacement reaction is characterized by the exchange of ions between two reactants to form new products. It can be represented as:

AB+CD→AD+CB

These reactions can result in:

i) Precipitate formation

• Common and classic outcome in double displacement reactions.
• Example:

BaCl₂+Na₂SO₄→BaSO₄↓+2NaCl

• BaSO₄ is a white precipitate.

ii) Evolution of a gas

• Some double displacement reactions release a gas.
• Example:

Na₂CO₃+2HCl→2NaCl+H₂O+CO₂↑

• Here, CO₂ gas evolves.

iii) Change in colour

• May occur due to:
• Formation of colored compounds
• Use of transition metal salts
• Example:

CuSO₄+NaOH→Cu(OH)₂↓+Na2SO₄

• Cu(OH)₂ is a blue precipitate, indicating a colour change.

Conclusion:

All three — precipitate formation, gas evolution, and colour change — are possible outcomes of double displacement reactions depending on the nature of the reactants.