Preparation of Ferrous Ammonium Sulphate (Mohr’s salt) - Procedure, FAQs

Ferrous Ammonium Sulphate

Here we are talking about the ferrous ammonium sulphate that means it contains ions of ammonia, iron and sulphate.as it is known that it is supposed to contain the two ions which are equally strong therefore it is said that it is a double salt reaction. Talking about the form in which it is available is the crystalline form and the crystals of this ferrous ammonium sulphate are blue-green in colour. Do you know what is the name of sulphate meaning in Hindi? गन्धक शुल्वारि.The ferrous ammonium sulphate formula is (NH₄)₂Fe(SO₄)₂·6H₂O.

There are various other physical properties of this ferrous ammonium sulphate. The first property to be discussed here is the melting point which is 100 degree celsius. It should be noted here that these salts in the compound dissolve in water to further give the aqua complex.

It is very important here to discuss the ferric ammonium sulphate formula or molecular formula of ferrous ammonium sulphate formula or chemical formula. It is given by: (NH₄)₂Fe(SO₄)₂.6H₂O with the chemical formula we will discuss the other chemical properties also which will start with its preparation.

Now we will discuss the preparation of the double salt of ferrous ammonium sulphate. preparation of ferrous sulphate.

We will now discuss the preparation of Mohr salt. To prepare a pure sample of ferrous ammonium sulphate it should be noted here that for preparing the Mohr’s salt the two equivalent quantities of salts are taken and those two salts are namely the hydrated ferrous sulphate and the ammonium sulphate.

The point which needs to be noted here that when the two of the salts are added and made the solution of it at that time a few drops of sulphuric acid needs to added and then the solution containing sulphuric acid will result in the formation of the crystals through the process called crystallisation.

Also read -

• NCERT Solutions for Class 11 Chemistry
• NCERT Solutions for Class 12 Chemistry
• NCERT Solutions for All Subjects

As we have discussed the preparation of the Mohr salt which is another of the ferrous ammonium sulphates. As we have said that the crystals are obtained at the end of the preparation and that too off the blue green colour then the shape of the crystals should also be known and the shape of the crystals are monoclinic.

As we have said that they are soluble in water then we should also know whether the crystals of ferrous ammonium sulphate are acid or base in nature? So the easiest way to determine the acidity or the basicity we need to know is that they turn the blue litmus paper or the solution red which means that they are acidic in nature.

Now we will discuss the preparation of Mohr salt in the complete experiment form

Aim: To prepare the crystals of Mohr's salt or the preparation of the double salt of ferrous ammonium sulphate.

Materials required: glass rod, beaker, funnel, wire gauze, burner, required salts, distilled water and a dilute sulphuric acid.

Theory: Here we are preparing the crystals of the Mohr salt or of the double salt of ferrous ammonium sulphate. It should be noted here that for preparing the Mohr’s salt the two equivalent quantity of salts are t when the two of the salts are added and made the solution of it at that time a few drops of sulphuric acid needs to added and then the solution containing sulphuric acid taken and those two salts are namely the hydrated ferrous sulphate and the ammonium sulphate which comprises what is called the double salt.

Procedure

• Firstly weight the equivalent weights of the two salts namely the ferrous sulphate and the ammonium sulphate
• On washing the flask so taken with the distilled water add to it the weighed salts of ferrous sulphate and the ammonium sulphate.
• When two of the salts are added and made the solution of it at that time a few drops of sulphuric acid needs to be added and then the solution contains sulphuric acid.
• Heat the solution to get the clear solution.
• Filter the solution using the filter paper.
• The point of crystallisation should be noted by again heating the solution up to that point and while it is heating to reach the crystallisation point the stirring should be done in order to not allow the salt to settle at the bottom.
• Once the crystallisation point is reached stop stirring the solution and allow it to cool at one place without much disturbance.
• Once the crystals are cooled they are separated by adding the mother liquor to it.
• Also check for the acidity and the basity using the litmus solution or the paper.

Also, students can refer to,

• NCERT Solutions for Class 12 Chemistry Chapter 13 Amines
• NCERT Exemplar Class 12 Chemistry Solutions Chapter 13 Amines
• NCERT Notes Class 12 Chemistry Chapter 13 Amines

Observations

• It is observed that the crystals are formed.
• The shape of the crystals obtained is monohedral.
• As the acidity or basicity is checked it is observed that the blue litmus paper turns red which shows its acidic nature.

Result: the yield for the crystals so obtained is calculated.

Precautions

• To get the clear solution it should not be heated at the high temperature rather it should be warm gently.
• While heating the solution the face should not be kept close to the beaker or the flask.
• The crystals obtained should not be disturbed while cooling otherwise proper shape would not be obtained.
• Stop heating once the crystallisation point is reached otherwise overheating may lead to the conversion of ions.

Another similar name which comes is ferric ammonium sulphate which has the chemical formula:(NH₄)₂Fe(SO₄)₂.6H₂O. Ferric ammonium sulphate is used as an indicator by the medicinal companies in preparation of certain medicines and this indicator is basically the standardised solution of ferrous ammonium sulphate where the ferrous ions are mixed with the sulphuric acid solution in proper amount of water to get it as indicator.
So here we have discussed each and every detail of the ferrous ammonium sulphate and about the crystals.

Preparation of Double Salt of Ferrous Ammonium Sulphate: Preparation of Double Salt: Ferrous Ammonium Sulphate (i) Dissolve 3.5 g of ferrous sulphate and 1.7 g of ammonium sulphate (weighed separately), in 5 mL of distilled water contained in a 50 mL conical flask by heating.

Also, check-

• NCERT Exemplar Class 11th Chemistry Solutions
• NCERT Exemplar Class 12th Chemistry Solutions
• NCERT Exemplar Solutions for All Subjects

NCERT Chemistry Notes :

• NCERT Notes Class 11 Chemistry
• NCERT Notes Class 12 Chemistry
• NCERT Notes For All Subjects