Question

‘Layer Test’ is used to identify

• A. Bromide
• B. Fluoride
• C. Potassium
• D. Water
• E. Chloride

Hint:

Layer test commonly used for bromide detection.

Answer 1

The Correct Option is A

Step 1: Understanding the 'Layer Test':
The 'Layer Test', also known as the solvent extraction test or CCl\(_4\)/CS\(_2\) test, is a confirmatory test in qualitative inorganic analysis used to distinguish between chloride, bromide, and iodide ions in solution.
Step 2: Detailed Explanation of the Procedure:
The test works as follows:
A small amount of the aqueous salt solution is taken in a test tube.
An organic solvent that is immiscible with water and can dissolve halogens, such as carbon tetrachloride (CCl\(_4\)), carbon disulfide (CS\(_2\)), or chloroform (CHCl\(_3\)), is added.
An oxidizing agent, typically fresh chlorine water, is added drop by drop and the mixture is shaken.
Principle: Chlorine is more electronegative than bromine and iodine, so it can displace them from their salt solutions: \[ \text{Cl}_2 + 2\text{Br}^- \rightarrow 2\text{Cl}^- + \text{Br}_2 \] \[ \text{Cl}_2 + 2\text{I}^- \rightarrow 2\text{Cl}^- + \text{I}_2 \] The liberated halogens (Br\(_2\) or I\(_2\)) are more soluble in the organic layer than in water. They dissolve in the organic solvent, imparting a characteristic color to it.
If Bromide (Br\(^-\)) is present, Br\(_2\) is formed, which gives an orange-brown or yellow-brown color to the organic layer.
If Iodide (I\(^-\)) is present, I\(_2\) is formed, which gives a violet or purple color to the organic layer.
If Chloride (Cl\(^-\)) is present, no reaction occurs with chlorine water, and the organic layer remains colorless.
The test is not used for Fluoride (F\(^-\)), as fluorine is the most electronegative element and cannot be displaced by chlorine.
Since the question asks what the test is used to identify, and Bromide is one of the key ions detected by this method, it is a correct choice. The test also identifies Iodide, but that is not an option.
Step 3: Final Answer:
The 'Layer Test' is used to identify Bromide (and Iodide) ions.