Q.Explain the 'Borax bead test'.

Borax dissolves in water to give an alkaline solution, which is why it is used as a cleansing agent.

Borax (sodium tetraborate, Na2B4O7·10H2O) is the salt of a strong base (NaOH) and a weak acid (boric acid, H3BO3). On dissolving in water, the borate ion hydrolyses, releasing OH- ions and making the solution alkaline (basic). Thi …

Boric acid (H3BO3) is polymeric because its planar B(OH)3 units are linked to one another by hydrogen bonds.

Each boric acid molecule, B(OH)3, is planar with three -OH groups. In the solid state, these -OH groups form extensive hydrogen bonds with the -OH groups of neighbouring B(OH)3 units, linking them into two-dimensional sheet-like (layered) structures. It is this network of hydrogen bonds — not the …

Borax, Na2B4O7·10H2O, is a salt of a strong base and a weak acid; such salts hydrolyse in water to give a basic (alkaline) solution.

Borax can be thought of as derived from sodium hydroxide (a strong base) and boric acid, H3BO3 (a weak acid). When a salt of a strong base + weak acid dissolves in water, the anion (from the weak acid) hydrolyses — it pulls a proton from water, releasing OH− ions and making the sol …

The statement is Right: borax's formula is Na2B4O7.10H2O.

Borax is the most important compound of boron, mined as a mineral and also manufactured industrially. Its full chemical name is sodium tetraborate decahydrate, and the accepted formula Na2B4O7.10H2O correctly shows 2 sodium ions, a tetraborate anion (B4O7 2-), and 10 water molecules of crystallisation. It is sometimes also written in the equivalent …

Calcium salts give a colourless bead, so they fail the borax bead test — option (d).

From NCERT Class 11 Chemistry (p-Block, boron/borax): heated borax gives sodium metaborate and boric anhydride (glassy bead):

Na₂B₄O₇ → 2NaBO₂ + B₂O₃. …