Experiment 18: IDENTIFYING THE Fe+++ 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
- K4[Fe(CN)6
- NH4CNS
- KMnO4
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: Orange
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. | No any ppt. was formed | Absence of Group II metal ions |
| 3. 2 ml of the original solution was taken in a clean and dry test tube and a double volume of NH4Cl was added and shaked. Then NH4OH solution was added. | Colour ppt. was formed | Presence of Group IIIA metal ions |
2. Confirmatory test:
Test of Fe+++ 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 HCl solution followed by K4[Fe(CN)6 solution were added to it. | Prussian blue colour was formed. | Presence of Fe+++ |
| 2. 2 ml of the original solution was taken in a clean and dry test tube and a few drops of HCl solution followed by K3[Fe(CN)6 solution were added to it. | No any colour was formed. | Presence of Fe+++ |
| 3. 2 ml of the original solution was taken in a clean and dry test tube and a few drops of HCl solution followed by NH4CNS solution was added to it. | Blood red colour was formed. | Presence of Fe+++ |
| 4. 2 ml of the original solution was taken in a clean and dry test tube and a few drops of NH4OH solution were added to it. | Reddish brown ppt. was formed. | Presence of Fe+++ |
| 5. 2 ml of the original solution was taken in a clean and dry test tube and a few drops of KMnO4 solution followed by dil.H2SO4 were added to it. | Pink colour was not discharged. | Presence of Fe+++ |
Reactions involved:
4Fe^{+++} + 3K_{4}[Fe(CN)]_{6} \rightarrow \underset{\underset{(Prussian\ blue)}{Ferric\ ferro\ cyanide}}{Fe_{4}[Fe(CN)_{6}]_{3}} + 12K^{+}\\
Fe^{+++} + NH_{4}CNS \rightarrow \underset{\underset{(Blood\ red)}{Ferric\ thiocyanate}}{Fe(CNS)_{3}} + NH_{4}^{+}\\
Fe^{+++} + 3NH_{4}OH \rightarrow \underset{Reddish\ brown\ ppt.}{Fe(OH)_{3}} + 3NH_{4}^{+}\\
RESULT
Hence, the sample was identified as Fe+++ basic radical.
CONCLUSION
Hence, we can test the basic radicals of a salt by wet ways testing the original solution with several reagents.
PRECAUTION
- Concentrated solutions should be handled carefully.
- The colour of the precipitate should be observed carefully.
- Check whether the original solution is clear and transparent.
Questions & discussion
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