Question

How do we prepare a `100*mL` of a `0.010*mol*L^-1` solution of `Fe^(2+)` in aqueous solution...?

Answer 1

If we use `"Mohr's salt"`, `(NH _4) _2 Fe(SO_4)_2 *6H_2O` whose molar mass is `392.13* g* mol^-1`. We need approx. `4*g` to prepare such a solution.

Explanation:

A `0.10*N` solution `-=` `0.10*mol*L^-1` is required.

Which, given a volume of `100*mL` constitutes a molar quantity of....

`-=0.10*mol*L^-1xx100xx10^-3*L=0.010*mol`

Which constitutes a mass of................

`0.010*molxx392.13*g*mol^-1=3.921*g`

Note that `"Mohr's salt"` is the standard `Fe(+II)` salt used in the laboratory, as it is stable with respect to oxidation.