Answer
See work below.
Work Step by Step
To know the protocol in which we can utilize to separate these hydroxides, we need to find the difference between them. Typically, looking at the classification of 5 groups of cations, we are able to sort them into groups and setup the procedure. However, this problem is a little bit tricky. Both $Fe(OH)_3$ and $Cr(OH)_3$ are base-insoluble hydroxides (group 3), so we cannot use the common scheme for this separation.
Thus, we must use a different property: amphoterism. $Cr(OH)_3$ happens to be an amphoteric hydroxide, while $Fe(OH)_2$ isn't. An amphoteric substance is a substance that can react with both acid and base; therefore, we can use a base to separate these hydroxides.
Let excess $NaOH$, a strong base, being added to the solid mixture. A portion of the mixture will dissolve ($Cr(OH)_3$), while the other part remains insoluble. Then, using filtration, we have $Fe(OH)_3$ as the predominant species of the solid.
