[Chemistry Class Notes] on Preparation of Mohr’s Salt or Ferrous Ammonium Sulphate Pdf for Exam

Mohr salt is a double swab containing ferrous sulphate and ammonium sulphate in equimolar quantities. Hence, when these two mariners are mixed in the rate of their molecular millions and also a hot logged result prepared, filtered and the hot filtrate cooled, light blue or green chargers of Mohr swab (octahedral in shape) are attained. 

Mohr’s swab is prepared by dissolving an equimolar admixture of doused FeSO₄.7H₂Oand ammonium sulphate in the water containing a little sulphuric acid. Take a clean 250 ml teacup; transfer 7 g of FeSO₄ and 3.5 g of ammonium sulphate chargers to it. Add 2.3 ml of dilute sulphuric acid to help hydrolysis. 200 ml of water is boiled for 5 twinkles. Add boiling hot water to the contents in small amounts. Now stir until mariners have fully dissolved. Sludge it and toast the filtrate in a demitasse dish till it concentrates to the Crystallisation Point. Place the demitasse dish for cooling for about 12 hours and collect the chargers of Mohr’s swab using the sludge paper. 

Compared the attained Mohr’s swab and original Mohr’s swab, using chemical styles similar as permanganometry and dichrometry system. Compare the attained Mohr’s swab and original Mohr’s swab using physical styles similar to FTIR spectroscopy, UV-Visible spectroscopy and melting point determination. 

Mohr’s salt is an inorganic compound which is a double salt with the formula (NH4)2Fe(SO4)2(H2O)6. It is a common laboratory reagent with IUPAC name ammonium iron(II) sulphate. Mohr’s salt is named after German Chemist Karl Fredrich Mohr.

Aim:

To prepare double salt ferrous ammonium sulphate or Mohr’s salt. 

Theory:

A double salt is a salt that contains an equimolar mixture of two salts with different cations but the same anion. Mohr’s salt is a double salt. So, when equimolar proportions of ferrous sulphate and ammonium sulphate are mixed to form a solution and then crystallised, we get crystals of ferrous ammonium salt or Mohr’s salt. The reaction can be shown as follows –

FeSO4       +         (NH4)2SO4       +      6H2O     🡪        FeSO4.(NH4)2SO4.6H2O

Ferrous             Ammonium            Water                  Ferrous Ammonium Sulphate  

Sulphate           Sulphate                                                        or Mohr’s Salt 

Iron(II) cations can undergo hydrolysis, therefore to prevent it while preparing their aqueous solution, a small amount of dilute sulphuric acid is added. 

Requirements:

Beaker, conical flask, trough, glass rod, tripod stand, funnel, wire gauze, weighing machine, ferrous sulphate, ammonium sulphate, distilled water, dilute sulphuric acid. 

Procedure: 

• Weigh 3.5 g of ferrous sulphate and keep it separately. 

• Weigh 1.7 g of ammonium sulphate and keep it separately. 

• Take a conical flask of 50ml and wash it with distilled water. 

• Now take 5ml of distilled water in the conical flask and add earlier weighed quantities of ferrous sulphate and ammonium sulphate. 

• Add 0.5ml of dilute sulphuric acid in the conical flask to prevent hydrolysis of iron cations. 

• Now gently warm the mixture (solution) to get a clear solution.

• Filter the solution. 

• Concentrate the solution(filtrate) by heating it till crystallisation point is reached. 

• Stir the solution occasionally while heating. 

• Allow the mixture to cool to room temperature. 

• After cooling the solution, you will get crystals of ferrous ammonium sulphate (green colored).

• Decant the mother liquor and separate the crystals.

• Now wash the crystals with water and alcohol mixture (1:1).

• Dry the crystals and note down the yield of the product.

Observation Table:

Result:

Yield of Mohr’s salt or ferrous ammonium sulphate is ________g.

Precautions: 

• For crystallisation, the solution should cool down slowly. 

• Do not disturb the solution while cooling during crystallisation. 

• Don’t overheat the solution for crystallisation. As it may change ferrous ions into ferric ions which will change stoichiometry of the solution. 

Mohr’s salt is largely used in analytical chemistry. Inhalation of Mohr’s salt causes irritation in the nose and throat. Over exposure of it can cause diarrhoea as well. So, while experimenting you need to be very careful.

This was all about preparation of Mohr’s salt, if you are looking for Mohr’s salt titrations which are important lab experiments of Class XII chemistry then you can go through the page ‘Mohr’s salt titration against potassium permanganate’. Many such articles are available on to help you. If you also wan
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