MolSynapsequestion bank

MolSynapse / Question bank / p-Block Elements: Groups 13 and 14 / Boron compounds: diborane, boric acid, borax, boron halides

JEE Advanced levelSingle correct optionDifficulty 3 of 3pb041

On gradual heating, orthoboric acid passes through which sequence of products?

A $HBO X_{2} \to B X_{2} O X_{3} \to H X_{2} B X_{4} O X_{7}$
B $H X_{2} B X_{4} O X_{7} \to HBO X_{2} \to B X_{2} O X_{3}$
C $B X_{2} O X_{3} \to HBO X_{2} \to H X_{2} B X_{4} O X_{7}$
D $HBO X_{2} \to H X_{2} B X_{4} O X_{7} \to B X_{2} O X_{3}$

Answer: D

Boric acid first loses one water to give metaboric acid (

HBO X_{2}

) near 370 K. Further heating (about 410 K) condenses four units to tetraboric acid,

H X_{2} B X_{4} O X_{7}

, and at red heat gives boron trioxide,

B X_{2} O X_{3}

, since more water is removed at each stage.

Practice p-Block Elements: Groups 13 and 14 More on Boron compounds: diborane, boric acid, borax, boron halides

Previous questionNext question

More questions on Boron compounds: diborane, boric acid, borax, boron halides