During the preparation of Mohr’s salt solution (Ferrous ammonium sulphate), which of the following acid is added to prevent hydrolysis of Fe2+ ion?
- dilute hydrochloric acid
- concentrated sulphuric acid
- dilute nitric acid
- dilute sulphuric acid
The Correct Option is D
Solution and Explanation
In the preparation of Mohr’s salt solution, it is essential to prevent the hydrolysis of the Fe2+ ions. Hydrolysis is a reaction where water reacts with a compound, affecting its stability. Ferrous ions (Fe2+) are prone to oxidation and hydrolysis, especially in an alkaline medium. To prevent these reactions, an acidic environment is maintained. The most suitable acid for this purpose is dilute sulphuric acid.
Here's why we use dilute sulphuric acid:
- Dilute sulphuric acid maintains an acidic medium, which is necessary for the stability of Fe2+ ions.
- It does not introduce any additional ions that could precipitate with Fe2+, ensuring a clear solution.
- Sulphuric acid is a strong acid, dissociating completely in water, providing an effective acidic environment without the risk of volatility or decomposition.
- Other acids, such as hydrochloric and nitric acid, could introduce volatile by-products or oxidizing agents, which can lead to unwanted side reactions or oxidation of the ferrous ions to ferric ions (Fe3+).
Therefore, among the given options, dilute sulphuric acid is the correct choice to prevent the hydrolysis of Fe2+ ion during the preparation of Mohr’s salt solution.
Top Questions on Hydrolysis of salts
- Which of the following substances does not undergo hydrolysis in aqueous solution?
- BITSAT - 2025
- Chemistry
- Hydrolysis of salts
- The complete hydrolysis of $ \text{ICl} $, $ \text{ClF}_3 $, and $ \text{BrF}_5 $, respectively, gives
- JEE Advanced - 2025
- Chemistry
- Hydrolysis of salts
Consider the following molecules:
The order of rate of hydrolysis is:- JEE Main - 2025
- Chemistry
- Hydrolysis of salts
- ‘X’ on hydrolysis gives two products. One of them is solid. What is ‘X’?
- AP EAPCET - 2024
- Chemistry
- Hydrolysis of salts
- Ba, Ca, Sr form halide hydrates. Their formulae are \( BaCl_2 \cdot xH_2O \), \( CaCl_2 \cdot yH_2O \), \( SrCl_2 \cdot zH_2O \). The values of \( x, y, z \) respectively are:
- AP EAPCET - 2024
- Chemistry
- Hydrolysis of salts
Questions Asked in NEET exam
- A body weighs 48 N on the surface of the earth. The gravitational force experienced by the body due to the earth at a height equal to one-third the radius of the earth from its surface is:
- NEET (UG) - 2025
- Gravitational potential energy
A bob of heavy mass \(m\) is suspended by a light string of length \(l\). The bob is given a horizontal velocity \(v_0\) as shown in figure. If the string gets slack at some point P making an angle \( \theta \) from the horizontal, the ratio of the speed \(v\) of the bob at point P to its initial speed \(v_0\) is :
- NEET (UG) - 2025
- Pendulums
- An oxygen cylinder of volume 30 litre has 18.20 moles of oxygen. After some oxygen is withdrawn from the cylinder, its gauge pressure drops to 11 atmospheric pressure at temperature \(27^\circ\)C. The mass of the oxygen withdrawn from the cylinder is nearly equal to: [Given, \(R = \frac{100}{12} \text{ J mol}^{-1} \text{K}^{-1}\), and molecular mass of \(O_2 = 32 \text{ g/mol}\), 1 atm pressure = \(1.01 \times 10^5 \text{ N/m}^2\)]
- NEET (UG) - 2025
- Ideal-gas equation and absolute temperature
- A uniform rod of mass 20 kg and length 5 m leans against a smooth vertical wall making an angle of \(60^\circ\) with it. The other end rests on a rough horizontal floor. The friction force that the floor exerts on the rod is (take \(g = 10\) m/s\(^2\)):
- NEET (UG) - 2025
- Common forces in mechanics
- A wire of resistance \(R\) is cut into 8 equal pieces. From these pieces, two equivalent resistances are made by adding four of these together in parallel. Then these two are added in series. The net effective resistance of the combination is:
- NEET (UG) - 2025
- Resistance