Informal vs. Formal Assessments. In order to properly understand what informal assessments are, we should first differentiate them from formal assessments. Formal assessments are designed to tell how well a student has progressed as evaluated against other students.
Rusting of iron consists of the formation of hydrated oxide, Fe(OH) 3, FeO(OH), or even Fe 2 O 3 .H 2 O. It is an electrochemical process which requires the presence of water, oxygen and an electrolyte. In the absence of any one of these rusting does not occur to any significant extent.
Iron hydroxide or ferrous hydroxide is an inorganic compound with the formula Fe(OH)2. It is produced when iron salts, from a compound such as iron sulfate, are treated with hydroxide ions. Iron hydroxide is a white solid, but even traces of oxygen impart a greenish tinge. The air-oxidized solid is sometimes known as green rust.