28. Solving a chemistry problem

110. Wash water of galvanic production, with a content of Cr 6 ions up to 200 mg / l, after preliminary reduction of Cr 6 to Cr 3, is treated with a NaOH solution with a concentration of 0.1 mol / l. Write down the formula of the resulting colloidal solution, assuming that Cr 3 was contained in the form of sulfate.