Borax Formula MCQ - Practice Questions with Answers

It is the most important compound of boron. It is a white crystalline solid of formula Na₂B₄O₇⋅10H₂O. In fact, it contains the tetranuclear units [B₄O₅(OH)₄]^2-and correct formula; therefore, is Na₂[B₄O₅(OH)4].8H₂O. Borax dissolves in water to give an alkaline solution.

On heating, borax first loses water molecules and swells up. On further heating it turns into a transparent liquid, which solidifies into glass like material known as borax bead.

The metaborates of many transition metals have characteristic colours and, therefore, borax bead test can be used to identify them in the laboratory. For example, when borax is heated in a Bunsen burner flame with CoO on a loop of platinum wire, a blue coloured
Co(BO₂)₂ bead is formed.