The factor responsible for weak acidic nature of B–F bonds in BF₃ is

Solution

It is pπ-p π back bonding involving B and F. The smaller atoms show more back bonding.

Anhydrous AlCl₃ can not be obtained from which of the following reactions ?

The precious Ruby stone is

The role of fluorspar ( CaF₂) which is added in small quantities in the electrolytic reducation of alumina dissolved in fused cryolite (Na₃AlF₆) is

Solution

CaF₂ when added to fused Cryolite, lowers them.p.and increases the conductivity.

Which of the following does not exist in free form

Solution

Boron form different hydride of general formula B_nH_n+4 and B_nH_n+6 but BH₃ is unknown.

Silicon carbide is used as a/ an

Solution

Abrasive is tough material used for sharpening and grinding the uneven surfaces and silicon carbide is used for grinding glass.

Moissan boron is

Solution

Moissan boron is amorphous boron,obtained by reduction of B₂O₃ with Na or Mg. It has 95-98% boron and is black in colour.

The hardest substance amongst the following is

Aluminium hydroxide is soluble in excess of sodium hydroxide forming the ion

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