Detection of the acid radical present in the given inorganic salt by wet ways

Experiment 19: DETECTION OF THE ACID RADICAL PRESENT IN THE GIVEN INORGANIC SALT (S6)

OBJECTIVE

TO DETECT THE ACID RADICAL PRESENT IN THE GIVEN INORGANIC SALT (S6) BY WET WAYS

APPARATUS REQUIRED

1. Test tube
2. Test tube holder
3. Test tube stand

CHEMICALS REQUIRED

1. AgNO₃
2. BaCl₂
3. HNO₃
4. HCl
5. CCl₄
6. KMnO₄

THEORY

Qualitative inorganic analysis is concerned with detecting and identifying radicals present in inorganic salt or a mixture of salts. Inorganic salts are the outcome of the neutralization of acids with base. Each inorganic salt consists of two parts. The part contributed by acid is called acid radical or anion and the part contributed by base is called basic radical or cation. For example, in sodium chloride, which can be obtained by the neutralization of base NaOH with acid HCl, Na⁺ is the basic radical and Cl^– is the acid radical.

PROCEDURE

The original solution was prepared by dissolving the given salt sample in water. The sample was subjected to several tests to detect acid radicals in the salt.

PHYSICAL PROPERTIES

1. State: Crystalline solid
2. Colour: White
3. Odour: Odourless
4. Solubility: Soluble in water

OBSERVATION TABLE

Experiment	Observation	Inference
1. AgNO3 test: 2 ml of the original solution was taken in a clean and dry test tube which was acidified with dilute nitric acid and a few drops of AgNO3 solution was added to it.	Yellow ppt. was present which was insoluble in ammonia solution	May be presence of I–
2. BaCl2 test 2 ml of the original solution was taken in a clean and dry test tube and a few drops of barium chloride solution was added to it.	White ppt. was not formed.	Absence of SO4– –
3. Ring test 2 ml of the original solution was taken in a clean and dry test tube and double the volume of conc. H2SO4 was added. The content was cooled and freshly prepared FeSO4 was added through the test tube wall and allowed to stand for some time.	The brown-coloured ring was not formed at the junction of the two solutions.	Absence of NO3–

Confirmatory test for I^–

Experiment	Observation	Inference
2 ml of the original solution was taken in a clean and dry test tube. A Few drops of CCl4 was added. 1 crystal of KMnO4 was added. Conc. HCl was added and the solution was shaken well.	A Violet layer was formed at the bottom of the test tube.	Presence of I–

Reactions involved

RESULT

The acid radical present in the given inorganic salt was found to be I^– (Iodide ion).

CONCLUSION

We can detect the acid radical present in given inorganic salt by wet ways.

PRECAUTION

1. The test tube should be clean and dry.
2. Salt solution should be used in small amounts.
3. The salt solution should not be too concentrated.