Ammonium iron(II) sulfate (also known as Mohr's salt) is a hydrated, water-soluble double salt with a relative formula mass of 392.0.
The formula of ammonium iron(II) sulfate can be represented as M⋅xH2O\text{M}\cdot x\text{H}_2\text{O}M⋅xH2O, where M\text{M}M represents all the anhydrous ions present in their stoichiometric ratio.
Table 1 shows its composition by mass.
Table 1
| Element | % by mass |
|---|---|
| N\text{N}N | 7.14 |
| H\text{H}H | 5.10 |
| Fe\text{Fe}Fe | 14.23 |
| S\text{S}S | 16.38 |
| O\text{O}O | 57.15 |
In an analysis, it is found that the salt contains the ions NH4+\text{NH}_4^+NH4+, Fe2+\text{Fe}^{2+}Fe2+, and SO42−\text{SO}_4^{2-}SO42−.
Calculate the empirical formula of ammonium iron(II) sulfate and the value of x x\,x in M⋅xH2O\text{M}\cdot x\text{H}_2\text{O}M⋅xH2O.
Describe the chemical tests (with their reagents and observations), including ionic equations, that would confirm the identities of the three ions present.
