Question

We can detect $Br^{-}$ and $I^{-}$ by ‘Layer Test’ if present together. If true enter 1, else enter 0.

Answer 1

Hint: To solve this question, we must first understand the concept of Layer Test. Then we need to assess the test and check whether it can give the required result or information or not and then only we can conclude the correct answer.

Complete step by step answer:
Before we move forward with the solution of this given question, let us first understand some basic concepts:
The Layer Test is used to detect the presence of bromide ions and iodide ions in a solution (e.g., Lassaigne's test solution). The layer test is carried out by adding an organic solvent such as carbon disulphide or chloroform in the presence of nitric acid and chlorine water to the given solution.
Step 1: This test is a qualitative test involving redox reactions among halides. This type of test is used to detect the presence of iodide and bromide ions in a solution.
Step 2: The decreasing order of the reactivity of the halide ions is \[{I^ - } > {\text{ }}B{r^ - } > {\text{ }}C{l^ - } > {\text{ }}{F^ - }\] . The salts can be oxidized in water.
In the given question, if we add chlorine water and chloroform to the mixture of bromide ion and iodide ion, the following redox reactions take place:
\[2{I^ - } + {\text{ }}C{l_2} \to {I_2} + {\text{ }}2C{l^ - }\]
And, \[2B{r^ - } + {\text{ }}C{l_2} \to B{r_2} + {\text{ }}2C{l^ - }\]
Step 3: At first Iodide ion is oxidized by chlorine (and bromine) and forms iodine. Here the chloroform layer will show violet colour due to the presence of iodine.
Step 4: And after that, we will extract the aqueous layer which contains bromide ion and repeat the addition of chlorine water and chloroform.
In this case the chloroform layer will show orange yellow colour due to the presence of bromine.
Step 5: And Therefore, we can detect and by ‘Layer Test’ if present together. Hence we will enter 1.

Note: Here, chlorine as an oxidant and chloride ions are negated here. Chlorine is almost colourless and it will be invisible in the chlorinated solvents as it is a gas.