Question

When a student added a few drops of barium chloride solution to sodium sulphate solution, he obtained a white precipitate instantly. Which of the following type of chemical reaction has been carried out by the student ?
(1) combination
(2) double displacement
(3) displacement
(4) decomposition

Answer 1

A student added a few drops of barium chloride ($\sf{BaCl_2)}$ solution to sodium sulphate $\sf{(Na_2SO_4)}$ solution.

The reaction will be like that

$\sf{BaCl_2+Na_2SO_4 \rightarrow BaSO_4+NaCl}$

Balanced Reaction:-

$\sf{BaCl_2+Na_2SO_4 \rightarrow BaSO_4+2NaCl}$

$\sf{BaCl_2\:=\:Ba^{2+}+Cl^{-}}$

$\sf{Na_2SO_4\:=\:Na^{+}+Cl^{-}}$

Here, positively charged ions are called Cation and negatively charged ions are called Anions.

A cation $\sf{Ba^{2+}}$ reacts with $\sf{SO_4^{2-}}$ anion. Similarly, $\sf{Cl^{-}}$ which is a anion reacts with a cation $\sf{Na^{+}}$ and forms products like $\sf{BaSO_4}$ which is a white precipitate and $\sf{NaCl}$

$\sf{BaCl_2(aq)+Na_2SO_4(aq) \rightarrow BaSO_4(s)+2NaCl(aq)}$

When Barium Chloride reacts with Sodium Sulphate solution, exchange of ions takes place and Barium Sulphate and Sodium Chloride are formed as a product. Also, the Barium Chloride which is obtained is produce white precipitate.

So, the reaction carried out by the student is Double Displacement Reaction.

Option 2) Double Displacement Reaction

Answer 2

When a student added a few drops of barium chloride solution to sodium sulphate solution, he obtained a white precipitate instantly, double displacement been carried out by the student.

Explanation:

The production of barium sulphate forms a white precipitate, while sodium chloride resides in the solution.

The chemical reaction is given below

Barium chloride + sodium sulphate --> barium sulphate (s) + sodium chloride (aq)

which can be called as double displacement reaction because

there it replaces the chlorine ion() and causes sodium to bind to chlorine.

Therefore the correct answer is option 2) double displacement