Magnetite is one of the most common iron minerals and an important ore of iron.

It usually contains less than 0.1 percent carbon and 1 or 2 percent slag. So, it is the purest form of iron.

It reduces acidified potassium dichromate solution to a green-coloured chromic salt.

Double salts are salts containing more than one cation or anion and are obtained by combination of two different salts which are crystallised in the same regular ionic lattice. For example: Mohr's salt.

This compound does not exist.

It is Mohr's salt.

Stainless steel is made up of iron, aluminium and copper.

Nitriding is a heat treating process that diffuses nitrogen into the surface of a metal to create a case hardened surface.

It is called Fool's gold (iron pyrite).

Iron loses its activity when dipped in conc. nitric acid and becomes chemically inert.

It decolourises KMnO₄.

The temperature here is 1500 - 1600 degree celsius.

The limestone is added to convert rocky material into slag which melts and runs to the bottom. The heat of the furnace decomposes the limestone to give calcium oxide. Thus, it is used as a flux.

Steel iron rod becomes hard and brittle on immersing in water.

Electron configuration of Fe: [Ar] 3d⁶ 4s². If 2 electrons are removed then number of electrons left would be 6 and thus, there would be 4 unpaired electrons.