Question

State True or False.

We can detect $B{r}^{-}$ and $I^{-}$ by 'Layer Test' if present together.

• A. True
• B. False

Answer 1

The correct option is A True

When bromide ion and iodide ion are present toghether, they can be detected by layer test.
The decreasing order of the reducing power is $I^{-}>B{r}^{-}>C{l}^{-}>F^{-}$.
In the mixture of bromide ion and iodide ion, add chlorine water and chloroform.
$2I^{-}+C{l}_2⟶\underset{violet}{I_2}+2C{l}^{-}$
$2B{r}^{-}+C{l}_2⟶\underset{orange-yellow}{B{r}_2}+2C{l}^{-}$
Iodide ion is oxidized by chlorine (and bromine) to form iodine.
First, the chloroform layer will have violet colour due to presence of iodine.
Now extract the aqueous layer containing bromide ion and repeat the addition of chlorine water and chloroform. Now the chloroform layer will have orange yellow colour due to presence of bromine.