Question

When sodium sulphate solution reacts with barium chloride solution, the solution after the reaction contains mainly......
(A) barium sulphate
(B) sodium chloride
(C) a and b both
(D) none of a and b

Answer 1

Hint: The reaction gives a double displacement reaction. In the reaction, ions are exchanged, when the sodium sulphate solution reacts with the barium chloride solution.

Complete step by step solution:
Double displacement reactions can be characterized as chemical reactions in which each of the two reacting molecules is exchanged for the product to form one part. The cations and anions of two different compounds exchange places during this reaction, forming two completely different compounds.
The 'barium chloride solution' reacts with sodium sulphate, resulting in a double displacement reaction in which ions are exchanged.
Therefore, sodium chloride and barium sulphate are formed. In water, the solution now consists only of sodium chloride.
This is because barium sulphate does not dissolve in water whereas sodium chloride dissolves in water. It settles down and the thus shaped precipitate is whitish in color. The reaction is
 $ N{a_2}S{O_4} + BaCl \to 2NaCl + BaS{O_4} $
The solution in water consists only of sodium chloride because sodium chloride dissolves in water when barium sulphate settles down and a white precipitate is formed in this reaction (insoluble).
Hence, option B-Sodium Chloride is the correct answer.

Note:
It is possible to further identify double displacement reactions as reactions of neutralization, precipitation and gas formation.
Neutralization reactions are a form of double displacement reaction that is unique. When an acid reacts with the same amount of base, an acid-based reaction occurs. The acid base reaction results in salt (neutral in nature) and water being formed.
Precipitation is the formation of a solid during a chemical reaction in a solution or within another solid. This process typically occurs when the dissolved ion concentration in the solution reaches the solubility product.
Gas Formation: To form gaseous hydrogen sulphide, several sulfide salts can react with acids. The breakdown of unstable double displacement reaction products also forms insoluble gases.