Question

Chlorine gas is passed into a solution of KF, KI and KBr and $CHCl_{3}$ is added. There is a colour in $CHCl_{3}$ layer. It is due to

• A. formation of $I_{2}$ (violet)
• B. formation of $Br_{2}$ (orange)
• C. formation of both $I_{2}$ and $Br_{2}$
• D. formation of $F_{2}$ (colourless).

Answer 1

Answer: (C)

formation of both $I_{2}$ and $Br_{2}$

Answer 2

The standard reduction potential of $Cl_{2}, I_{2}, Br_{2}$ and $F_{2}$ is $I_{2}+2e^{-}$ ${ -> }$ $2l^{-} ; E^{o} =+0.54 V$ $Br_{2}+2e^{-}$ ${ -> }$ $2Br^{-} ; E^{o} =+1.09 V$ $Cl_{2}+2e^{-}$ ${ -> }$ $2 Cl^{-} ; E^{o}=+1.33 V$ $F_{2}+2e^{-}$ ${ -> }$ $2F^{-} ; E^{o}=+2.87 V$ From the data given above it is clear that $cl_{2}$ can oxidize both $I^{-}$ and $Br^{-}$, the colour in $CHCl_{3}$ layer will be obviously due to the formation of $I_{2}$ and $Br_{2}$ both.