Question

What will you observe when blue litmus is introduced into a solution of ferric chloride?

Answer 1

Ferric chloride solution.

• Ferric chloride $\left({\mathrm{FeCl}}_3\right)$ reacts with water $\left({\mathrm{H}}_2\mathrm{O}\right)$ to form ferric hydroxide $\left(\mathrm{Fe}{\left(\mathrm{OH}\right)}_3\right)$ and hydrochloric acid $\left(\mathrm{HCl}\right)$ making the solution acidic.

${\mathrm{FeCl}}_3\left(\mathrm{aq}\right)+3{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to \mathrm{Fe}{\left(\mathrm{OH}\right)}_3\left(\mathrm{s}\right)+3\mathrm{HCl}\left(\mathrm{aq}\right)$

Acid	Blue litmus to red
Base	Red litmus to blue

• So, blue litmus will turn red due to the presence of hydrochloric acid.
• Therefore, ferric chloride will turn blue litmus red.