Ferrous Ion Test Present in Ferrous Sulphate Solution

Experiment 6: Ferrous Ion Test Present in Ferrous Sulphate Solution

OBJECTIVE

TO TEST FERROUS IONS PRESENT IN FRESHLY PREPARED FERROUS SULPHATE SOLUTION AND OXIDIZE IT TO FERRIC ION [FERROUS-FERRIC SYSTEM].

APPARATUS REQUIRED

1. Beaker
2. Test tube holder
3. Test tube
4. Burner
5. Glass Tube

CHEMICAL REQUIRED

1. FeSO₄
2. Dil. H₂SO₄
3. Conc. HNO₃
4. NH₄CNS
5. NH₄OH
6. K₃[Fe(CN)₆
7. K₄[Fe(CN)₆
8. KMnO₄

THEORY

A redox reaction is a reaction in which oxidation and reduction take place side by side. The chemical process which involves an increase in oxidation number is called oxidation and the chemical process which involves a decrease in oxidation number is called reduction The chemical substance which oxidizes others but itself gets reduced is called an oxidizing agent The chemical substance which reduces other but gets oxidized is called Reducing agent.

When ferrous sulphate is allowed to react with conc. nitric acid in the presence of dil. H₂SO₄, the ferrous sulphate is oxidized to ferric sulphate.

Here, conc. HNO₃ acts as an oxidizing agent and FeSO₄ acts as a reducing agent.

PROCEDURE

2 gm of ferrous sulphate salt was taken in a beaker and its solution is prepared by adding water to make the original solution (OS). Then test of ferrous ions was carried out.

TEST OF FERROUS ION

Experiment	Observation	Inference
i. 2 ml of OS is taken in a clean and dry test tube and a few drops of K4[Fe(CN)6 is added.	Deep blue ppt. is formed	Presence of Fe++ in OS
ii. 2 ml of OS is taken in a clean and dry test tube and a few drops of K3[Fe(CN)6 is added.	Blueish white ppt. is formed.	Presence of Fe++ in OS
iii. 2 ml of OS is taken in a clean and dry test tube and a few drops of KMnO4 is added followed by dil. H2SO4.	Pink colour of KMnO4 is discharged	Presence of Fe++ in OS
iv. 2 ml of OS is taken in a clean and dry test tube and a few drops of NH4OH is added.	Dirty green ppt. is formed	Presence of Fe++ in OS
v. 2 ml of OS is taken in a clean and dry test tube and a few drops of NH4CNS is added.	No ppt. or colouration is seen	Presence of Fe++ in OS

After performing the above test of Fe⁺⁺ ion, the original solution is converted or oxidized into Fe⁺⁺⁺ ion.

5 ml of OS was taken in a beaker and an equal volume of dilute sulphuric acid was added followed by 5 to 6 drops of nitric acid. The solution was boiled for some time and the colour was changed to yellow. The solution was cooled and one test tube of water was added to it. This oxidized sample is termed as a sample solution (SS). The test of Fe⁺⁺⁺ ion in SS was performed.

TEST OF FERRIC ION

Experiment	Observation	Inference
i. 2 ml of SS is taken in a clean and dry test tube and a few drops of K4[Fe(CN)6 is added.	Prussian blue or Deep blue ppt. is formed	Presence of Fe+++ in SS
ii. 2 ml of SS is taken in a clean and dry test tube and a few drops of K3[Fe(CN)6 is added.	No ppt. or green ppt. is formed.	Presence of Fe+++ in OS
iii. 2 ml of SS is taken in a clean and dry test tube and a few drops of KMnO4 is added followed by dil. H2SO4.	Pink colour of KMnO4 is not discharged	Presence of Fe+++ in OS
iv. 2 ml of SS is taken in a clean and dry test tube and a few drops of NH4OH is added.	Brown ppt. is formed	Presence of Fe+++ in OS
v. 2 ml of SS is taken in a clean and dry test tube and a few drops of NH4CNS is added.	Blood red colouration is seen	Blood-red colouration is seen

Reactions involved: For Fe²⁺ ion

For Fe³⁺ ion

RESULT

The presence of ferrous ion is confirmed in the given ferrous solution and Ferric solution is prepared from the Ferrous solution

CONCLUSION

Thus, we can get ferric ions from Ferrous ions by an oxidation reaction and able to get a clear concept of ferric and ferrous ion by an oxidation reaction and able to get a clear concept of ferric and ferrous ions by studying various chemical reagents

PRECAUTIONS

1. Apparatus should be handled with care.
2. Ferrous ion is carefully oxidized to ferric ion.
3. Reagents should be carefully added.