Question

Aqueous solution of Mohr's salt gives a positive test for:

• A. Fe\(^{2+}\)
• B. NH\(_4^+\)
• C. SO\(_4^{2-}\)
• D. All of these

Hint:

Mohr's salt is a useful reagent in analytical chemistry, especially for detecting iron(II) ions and performing sulfate ion tests. It is commonly used in titrations for determining the concentration of iron(II) in samples.

Answer 1

The Correct Option is D

Mohr's salt, which is a double salt of ammonium iron(II) sulfate, has the chemical formula \((NH_4)_2Fe(SO_4)_2 \cdot 6H_2O\). When dissolved in water, it dissociates to release the following ions:
Fe\(^{2+}\) ions (iron(II) ions) - NH\(_4^+\) ions (ammonium ions)
SO\(_4^{2-}\) ions (sulfate ions)

Thus, the aqueous solution of Mohr's salt contains Fe\(^{2+}\), NH\(_4^+\), and SO\(_4^{2-}\) ions, and all of these can be detected by specific tests:
Fe\(^{2+}\) gives a positive test with potassium ferrocyanide (producing a blue precipitate).
NH\(_4^+\) ions can be detected using Nessler's reagent, which gives a yellow to brown color.
SO\(_4^{2-}\) ions can be detected using barium chloride, which gives a white precipitate of barium sulfate.

Therefore, the correct answer is (D) All of these.