When a compound ammonium iron(II) sulphate was heated. the green crystals seem to turn yellow why is this?
Corrie writes…. Iron(II) compounds are readily oxidised in air, especially in solution. Thus iron(II) sulphate solution gradually turns yellow-brown and cloudy as a precipitate of iron(III) hydroxide forms. The yellow colour you are observing is therefore most probably due to a similar oxidation, as the water of crystallisation is lost and some iron(III) salt is formed. Strong heating of iron(II) sulphate crystals ultimately leads to the formation of iron(III) oxide, which is reddish-brown. Risk assessment Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on what is said on this website. For further guidance see our tutorial on Risk Assessment.
