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

When barium chloride is reacted with sodium sulphate then a white precipitate of barium sulphate and aqueous solution of sodium chloride salt is obtained.
${\mathrm{BaCl}}_2\left(\mathrm{aq}\right)+{\mathrm{Na}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)\to \mathrm{Ba}\left({\mathrm{SO}}_4{)}_2\right(\mathrm{aq})+\mathrm{NaCl}(\mathrm{aq})$
So, the following reaction is an example of double displacement reaction.

Hence, the correct answer is option 2.