Question

${\mathrm{BaCl}}_2\left(\mathrm{aq}\right)+{\mathrm{Na}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)\to {\mathrm{BaSO}}_4\left(\mathrm{s}\right)+2\mathrm{NaCl}\left(\mathrm{aq}\right)$

If ${\mathrm{Na}}_2{\mathrm{SO}}_4$(aq) in the above reaction is replaced with dilute ${\mathrm{H}}_2{\mathrm{SO}}_4$:

• A. No reaction will takes place.
• B. ${\mathrm{BaSO}}_4$ precipitate will be formed.
• C. ${\mathrm{BaSO}}_4$ will be formed but will not precipitate as it is soluble in dilute ${\mathrm{H}}_2{\mathrm{SO}}_4$.
• D. $\mathrm{NaCl}$ will precipitate due to a low pH.

Answer 1

The correct option is B

${\mathrm{BaSO}}_4$ precipitate will be formed.

Explanation for the correct option:

1. Double displacement reaction: A reaction in which two ionic compounds by mutual exchange of their ions to give two other products. Generally one of the products in a double displacement reaction is insoluble, gets precipitated out.
2. If ${\mathrm{Na}}_2{\mathrm{SO}}_4$(aq) in the above reaction is replaced with dilute ${\mathrm{H}}_2{\mathrm{SO}}_4$ (Sulphuric acid), Barium sulphate(${\mathrm{BaSO}}_4$) and Hydrochloric acid($\mathrm{HCl}$) will be formed.
3. Reaction can be given as: $$\begin{gathered} {\mathrm{BaCl}}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)\to {\mathrm{BaSO}}_4\left(\mathrm{s}\right)\downarrow +2\mathrm{HCl}\left(\mathrm{aq}\right) \\ (\mathrm{Barium}\mathrm{chloride})(\mathrm{Sulphuric}\mathrm{acid})\underset{\left(\mathrm{White}\right)}{\underbrace{(\mathrm{Barium}\mathrm{sulphate})}}(\mathrm{Hydrochloric}\mathrm{acid}) \end{gathered}$$.
4. Here, when Barium chloride(${\mathrm{BaCl}}_2$) solution is added to ${\mathrm{H}}_2{\mathrm{SO}}_4$ a white precipitate of Barium sulphate is formed.
5. The precipitate is insoluble in dil. Hydrochloric acid.

Explanation for the incorrect options:

1. Option (A) is incorrect because this reaction is a double displacement reaction.
2. Option (C) is incorrect because a white precipitate of Barium sulphate $\left({\mathrm{BaSO}}_4\right)$ will form here which is insoluble in Hydrochloric acid $\left(\mathrm{HCl}\right)$.
3. Option (D) is incorrect because Sodium chloride $\left(\mathrm{NaCl}\right)$ will not precipitate out, but Barium sulphate will get precipitated out.

Therefore, the option (B) is correct. i.e., If ${\mathrm{Na}}_2{\mathrm{SO}}_4$(aq) in the above reaction is replaced with dilute ${\mathrm{H}}_2{\mathrm{SO}}_4$, ${\mathrm{BaSO}}_4$ precipitate will be formed.