Question

When sodium sulphate solution and barium chloride solution are mixed together, the colour of precipitate formed is:

• A. Yellow
• B. Green
• C. White
• D. Red

Answer 1

The correct option is C

White

Explanation for correct answer

C. White: In the aqueous phase, compounds remain in their ionic form. When an aqueous solution of two compounds is mixed, there occurs an exchange of ions between the reactants leading to the formation of two new compounds in the solution. This is called a double displacement reaction.

Sodium sulphate $\left({\mathrm{Na}}_2{\mathrm{SO}}_4\right)$ and barium chloride $\left({\mathrm{BaCl}}_2\right)$ remain in ionic form in their aqueous solution. When the aqueous solutions of these compounds are mixed, a double displacement reaction takes place involving the exchange of chloride and sulphate ions. The product formed is a solid precipitate of barium sulphate$\left({\mathrm{BaSO}}_4\right)$. Sodium chloride $\left(\mathrm{NaCl}\right)$ is also formed in the reaction which remains in the solution.

The chemical equation for the reaction is:

$$\begin{gathered} {\mathrm{Na}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)+{\mathrm{BaCl}}_2\left(\mathrm{aq}\right)\to {\mathrm{BaSO}}_4\left(\mathrm{s}\right)+2\mathrm{NaCl}\left(\mathrm{aq}\right) \\ (\mathrm{Sodium}(\mathrm{Barium}(\mathrm{Barium}(\mathrm{Sodium} \\ \mathrm{sulphate})\mathrm{chloride})\mathrm{sulphate})\mathrm{chloride}) \end{gathered}$$

The colour of the precipitate will be the colour of pure barium sulphate. Barium sulphate is a white crystalline solid.

The correct option is (C) White. When sodium sulphate solution and barium chloride solution are mixed together, the colour of precipitate formed is white.