IDENTIFYING THE Cu++ BASIC RADICAL PRESENT IN GIVEN INORGANIC SALT

Experiment 16: IDENTIFYING THE Cu++ BASIC RADICAL PRESENT IN GIVEN INORGANIC SALT

OBJECTIVE:

TO IDENTIFY THE BASIC RADICAL PRESENT IN GIVEN INORGANIC SALT

APPARATUS REQUIRED

• Test tube
• Test tube holder

CHEMICALS REQUIRED

• Dil. HCl
• H₂S
• NH₄OH
• NH₄Cl
• KI
• NaOH
• K₄[Fe(CN)₆
• Na₂S₂O₃

THEORY

Qualitative inorganic analysis is concerned with the detection and identification of 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 the basic radical of the salt.

OBSERVATION

1. Preliminary test:

a. State: Solid
b. Odour: Odourless
c. Colour: Blue
d. Solubility: Soluble in water

Group Separation Table

Experiment	Observation	Inference
1. 2 ml of the original solution was taken in a clean and dry test tube and a few drops of dil. HCl was added to it.	White ppt. was not formed	Absence of Group I metal ions
2. The solution above was passed to the H2S solution	Black ppt. was formed	Presence of Group II metal ions

2. Confirmatory test:

Test of Cu⁺⁺ ion

Experiment	Observation	Inference
1. 2 ml of the original solution was taken in a clean and dry test tube and a few drops of NaOH solution were added to it.	Blueish white ppt. was formed which turned to black when boiled.	Presence of Cu++
2. 2 ml of the original solution was taken in a clean and dry test tube and a few drops of NH4OH solution was added to it.	Blue ppt. was formed which dissolved in excess NH4OH and gave a deep blue solution.	Presence of Cu++
3. 2 ml of the original solution was taken in a clean and dry test tube and a few drops of K4[Fe(CN)6 solution were added.	Reddish brown ppt. was formed.	Presence of Cu++
4. 2 ml of the original solution was taken in a clean and dry test tube and a few drops of KI solution was added to it.	Brown ppt. was formed. White ppt. was seen on adding Na2S2O3.	Presence of Cu++

Reactions involved:

RESULT

Hence, the sample was identified as Cu⁺⁺ basic radical.

CONCLUSION

Hence, we can test the basic radicals of a salt by wet ways testing the original solution with several reagents.

PRECAUTION

1. Concentrated solutions should be handled carefully.
2. The colour of the precipitate should be observed carefully.
3. Check whether the original solution is clear and transparent.