Preparation of iron (II) hydroxide

A green-gray precipitate is reversibly formed.

Scientific name: Insoluble iron (II) hydroxide is formed when iron (II) sulfate is treated with alkali. The acid dissolves the precipitate.


Precipitation Reaction: Iron (II) Sulfate and Sodium Hydroxide

by Doctor Tang

Получение гидроксида железа (II)

by paramitacenter


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Reaction formula

FeSO4 + 2KOH → Fe(OH)2 + K2SO4

Fe(OH)2 + 2HCl → FeCl2 + 2H2O

Step-by-step instruction

  1. To obtain iron (II) hydroxide mix the solutions of iron (II) sulfate and potassium hydroxide in a flask
  2. The green-gray precipitate is formed
  3. To test the action of an acid on iron (II) hydroxide put a few drops of hydrochloric acid solution to the flask. The solution become yellow and clear

Scientific background

Iron (II) sulfate reacts with potassium hydroxide producing iron (II) hydroxide and potassium sulfate. The exchange reaction between soluble salt and alkali is the common way to obtain insoluble hydroxides. The iron (II) sulfate under the action of alkali forms a green-gray precipitate. The addition of hydrochloric acid dissolves the precipitate turning iron (II) hydroxide back to iron (II) chloride.


Published on 09 September 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst