Reactions in which there is an exchange of ions between the reactants are called?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Double Displacement
In a double displacement reaction, two compounds exchange their ions to form two new compounds. For example, sodium sulphate and barium chloride exchange ions to give a white precipitate of barium sulphate and sodium chloride:
\(\ce{Na2SO4 + BaCl2 -> BaSO4 + 2NaCl}\)
Why the other options are incorrect
Option (1) Decomposition — Incorrect. Here a single reactant breaks down into two or more simpler products, as calcium carbonate gives lime and carbon dioxide on heating.
Option (2) Displacement — Incorrect. Here a more reactive element pushes out a less reactive one from its compound, as iron displaces copper from copper sulphate; only one exchange takes place.
Option (4) Corrosion — Incorrect. It is the slow eating away of a metal by air, moisture or acids, as in the rusting of iron.