NEET-UG and JEE Main Chemistry · Class 12
Preparation of Mohr's salt and potash alum — NEET & JEE Questions
Preparation of Mohr's salt and potash alum is a topic in Principles Related to Practical Chemistry, a Class 12 Chemistry chapter of the NEET-UG and JEE Main syllabus. TestBudy holds 12 published NEET-UG and JEE Main questions on Preparation of Mohr's salt and potash alum, each with the marking scheme of the real paper.
- questions
- 12
- shown here
- 10
Five free tests with an account. Your score comes with the result; where you stand is Pro.
Preparation of Mohr's salt and potash alum MCQs with solutions
10 of the 12 published questions on this topic, exactly as they appear in a test. Answers and worked solutions come with your result rather than on this page.
What type of compound is Mohr's salt, FeSO4·(NH4)2SO4·6H2O?
- A. A double salt
- B. A coordination compound
- C. A simple binary salt
- D. A covalent molecular solid
Why is a small amount of dilute sulphuric acid used while preparing crystals of Mohr's salt?
- A. It precipitates metallic iron from the solution
- B. It limits Fe2+ hydrolysis and oxidation
- C. It converts ammonium ions into ammonia gas
- D. It removes sulphate ions from the mixture
Mohr's salt is a double salt containing ferrous sulfate and
- A. ammonium sulfate
- B. sodium sulfate
- C. potassium chloride
- D. calcium carbonate
Potash alum is commonly represented as a hydrated double sulfate of potassium and
- A. aluminium
- B. iron(II)
- C. copper
- D. calcium
A hot concentrated solution used to prepare a double salt is allowed to cool slowly. What is the main purpose of this step?
- A. To evaporate all water instantaneously
- B. To decompose the salt into its component metals
- C. To crystallise the salt as the solution cools
- D. To convert the dissolved ions into gases
During crystal preparation, why are the separated crystals washed with only a small amount of cold washing liquid?
- A. To convert the double salt into a coordination compound
- B. To increase the solubility of the product as much as possible
- C. To melt the crystals before drying
- D. To clean crystals while minimising product loss
Why is a small amount of dilute sulfuric acid commonly added during preparation of Mohr's salt?
- A. To help prevent hydrolysis and oxidation of ferrous ions
- B. To precipitate iron as hydroxide
- C. To oxidise Fe2+ completely to Fe3+
- D. To remove all sulfate ions
After preparing a hot concentrated solution for crystallisation, why is it cooled slowly?
- A. To allow well-formed crystals to separate as solubility decreases
- B. To keep all solute dissolved
- C. To decompose the double salt
- D. To evaporate all water instantly
A student obtains very little potash alum after concentrating the solution but filters it while it is still hot. What is the most likely reason for the low yield?
- A. The alum was still dissolved in the hot solution
- B. The alum had already changed into metallic aluminium
- C. Hot filtration always destroys sulphate ions
- D. Potassium ions evaporated from the solution
A student washes freshly prepared crystals with a large volume of hot water. What is the most likely consequence?
- A. Loss of product because more crystals dissolve
- B. Higher yield because hot water precipitates the salt
- C. No effect because solubility never changes with temperature
- D. Conversion of crystals into metal
Common mistakes in Preparation of Mohr's salt and potash alum
Recorded against questions in this topic that are not shown above, so none of these points at an answer you can see on this page.
- Treats solvent adhering to crystals as part of the product mass.
- Assumes more aggressive heating and washing always improve crystallisation.
Practise this chapter
Reading a question and answering it under a clock are different things. A chapter-length test measures whether the topic went in.