Question

Chlorine gas is bubbled into the water and subsequently, some blue litmus solution is poured into the water. Predict the observations that would follow.

Answer 1

Litmus test:

• When Chlorine(${\mathrm{Cl}}_2$) gas is bubbled through water it produces Hypochlorous($\mathrm{HOCl}$) acid, which further decomposes into Hypochlorite(${\mathrm{OCl}}^{-}$) ions and Hydrogen(${\mathrm{H}}^{+}$) ions.
• The reaction would be: $\underset{(\mathrm{Chlorine}\mathrm{gas})}{\underbrace{{\mathrm{Cl}}_2\left(\mathrm{g}\right)}}+\underset{\left(\mathrm{Water}\right)}{\underbrace{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}}\to \underset{(\mathrm{Hypochlorous}\mathrm{acid})}{\underbrace{\mathrm{HOCl}\left(\mathrm{aq}\right)}}+\underset{(\mathrm{hypochlorite}\mathrm{ion})}{\underbrace{{\mathrm{OCl}}^{-}\left(\mathrm{aq}\right)}}+\underset{(\mathrm{Hydrogen}\mathrm{ion})}{\underbrace{{\mathrm{H}}^{+}\left(\mathrm{aq}\right)}}$
• Due to the formation of Hypochlorous acid, the blue litmus solution poured into water will turn red.
• Litmus turns blue to red when it is treated with an acidic solution.