Question

Identify the characteristics of a precipitation reaction:
(A) Insoluble solid is formed
(B) generally proceeds via a double displacement reaction
(C) coloured solid is formed
(D) both (A) and (B)

Answer 1

Hint: In this reaction, with the dissociation of the two ionic salts in the solution, along with the exchange of their ions and forming two new compounds, out of which one separates out as solid in the solution.

Complete step by step solution:
In the precipitation reaction, there are two soluble ionic salts which on dissolving in the water, dissociate into its ions and form two new ionic salts, such that one of the salts is insoluble and separates out. This insoluble compound is called the precipitate.
During the reaction, it is seen that in the solution, the ions replace another ion with the same charge, that is, either the cation or the anion. So, involving the exchange of either the two cations or the anions from their original bonds in the reactant. Thus, forming two new products through a double displacement reaction.
For example: on mixing the solution of silver nitrate and potassium chloride. They dissociate into its constituent ions in the solution and then exchange position of either the cations $(A{{g}^{+}}\,and\,{{K}^{+}})$ or the anions $(NO_{3}^{-}\,and\, C{{l}^{-}})$, forming an insoluble salt of silver chloride, which is a white precipitate, through the double displacement reaction.
The reaction is as follows: $AgN{{O}_{3}}(aq)+KCl(aq)\to AgCl(s)+KN{{O}_{3}}(aq)$

Therefore, the characteristics of the precipitation reaction are option (D) the formation of insoluble solid and the reaction generally proceeds via double displacement.

Note: The insoluble precipitate can be separated from the solution by simple filtration, decantation or centrifugation. Thus, made use of in the waste water treatment plants. Also, due to the presence of the salts as ions in the solution, it helps in determining the various components of the solution.