Table of Contents
Why acid is added during preparation of Mohr salt?
Notes on Mohr’s Salt Dilute sulphuric acid is added to prevent the hydrolysis of ferrous sulphate. For dissolving the mixture of salts in water excessive heating is avoided. This is for the prevention of Fe2+ ions (light green) to Fe3+ ions (yellow).
Which acid is used in the synthesis of Mohr’s salt?
Preparation. Mohr’s salt is prepared by dissolving an equimolar mixture of hydrated ferrous sulfate and ammonium sulfate in water containing a little sulfuric acid, and then subjecting the resulting solution to crystallization. Ferrous ammonium sulfate forms light green crystals.
Why we add Dil h2so4 in Mohr’s salt?
To prepare double salts: ferrous ammonium sulphate (Mohr’s salt) and potash alum. Fe2+ and Al3+ ions undergo hydrolysis, therefore, while preparing aqueous solutions of ferrous sulphate and aluminium sulphate in water, 2-3 mL dilute sulphuric acid is added to prevent the hydrolysis of these salts.
Which is the oxidising agent in the kmno4 vs Mohr salt titration?
In this titration, potassium permanganate is the oxidizing agent and Mohr’s salt is the reducing agent. Mohr’s salt is a double salt of ferrous sulphate and ammonium sulphate and its composition is FeSO4.
Why acid is added to FAS?
Sulfuric acid is often added to solutions using ferrous ammonium sulfate in order to reduce the oxidation of the ferric iron. Ferrous ammonium sulfate is typically comprised of light green crystals in solid form.
Why is H2SO4 added to FAS K2Cr2O7 titration?
Just use H2SO4, since it can’t be oxidised further and is thus safe from K2Cr2O7. It’s because chloride ions can be oxidised by strong oxidising agents such as permanganate (but also some others) in a reaction that will produce chlorine: .
Why is Mohr salt not heated before titration?
Mohr’s salt is a very strong reducing agent. It reduces the (Mn+2) cation from KMnO4 at room temerature itself. Therefore it is not heated.
How do you do a titration of Mohr’s salt?
- Fill the burette by potassium permanganate solution.
- Take conical flask and add 5ml of dilute sulfuric acid in it.
- Pipette out 10 ml of prepared standard Mohr’s salt solution in the same conical flask.
- Place a white tile under the burette and place the conical flask containing Mohr’s salt solution and H2SO4 on it.
Why Dil H2SO4 is added before titration of kmno4 and Mohr’s salt?
To prevent the hydrolysis, Conc. H2SO4 needs to be added to the Mohr’s salt crystals during the preparation of its standard solution. Another reason is also to prevent the oxidation of Fe2+ ions of Mohr’s salt to Fe3+ ions.
What is the use of phosphoric acid in the standardization of KMnO4 by Mohr salt solution?
Phosphoric acid is added to reduce the electrode potential for the Fe3+ → Fe2+ reaction by stabilising the ferric ion.
Why ferrous sulphate is not used in titration instead of Mohr salt?
Mohr’s salt is not hygroscopic but FeSO4⋅7H2O is hygroscopic. Mohr’s salt contains only ferrous ions whereas ferrous sulphate contains some ferric ions. D. Mohr’s salt solution can be titrated even in the absence of H2SO4.