Solubility Equilibria Of Sparingly Soluble Salts

Mohr's salt is a double salt which contains two types of cations, specifically iron (Fe²⁺) and ammonium (NH₄⁺), and one type of anion, sulfate (SO₄^2-). Additionally, it includes water of crystallization.

Each unit of Mohr's salt is composed as follows:

• 1 molecule of ferrous sulfate (FeSO₄)
• 1 molecule of ammonium sulfate [(NH₄)₂SO₄]
• 6 molecules of water of crystallization (6H₂O)

Combining these components gives the chemical formula:

${\mathrm{Fe}\mathrm{SO}}_4{(\mathrm{NH})}_4{\mathrm{SO}}_4\cdot 6H_{2}O$

This is precisely the chemical formula of Mohr's salt. Therefore, the correct answer is: