Test: Group 13 Elements: Boron Group - JEE MCQ

Boron exists in giant covalent structure. Boron due to small size forms strong covalent bonds with the neighbouring atoms.

Melting point in group - 13 decreases down the group but the trend is not regular. Boron has the highest melting point because of its very strong covalent structure. Gallium has a very low melting point (29.8 K) and, therefore, could exist in liquid state during summer.

As radius of Boron is less than radius of Be hence IV statement is false while rest other are true statements.

Ga is little smaller or have slightly lower atomic radius due to poor Screening effect by inner 3d electrons.

As due to inert pair effect stability of lower oxidation state increases down the group. So order given in option 3 is incorrect and the correct order is in given in option 4 here. Properties given in option 1 and 2 are in correct order.

The total energy to produce a B³⁺ ion (or the sum of the first three ionization energies) is too large to be compensated by lattice energies (in case of solids) or by hydration energies (in aqueous solution).

Boron is not attacked by HCl; whilst Al reacts with HCl to from and .
A.

B. Halides of both are electron deficient, therefore, act as Lewis acids.
C.

The basicity of the dioxide alters in the order

The basicity increases on moving down the group. Thus, CO₂ and SiO₂ are purely acidic. GeO₂ is not as strongly acidic as SiO₂ . It is weakly acidic and weakly basic. SnO₂ and PbO₂ are definitely amphoteric.

Pyrex glass is obtained by fusing together 60 to 80% SiO₂ 10 to 25% B₂O₃ and remaining amount of Al₂O₃

This problem is based on preparation of inorganic benzene and structural charactristics of diborane. Student must be familiar with concept of bonding in diborane to solve this problem. Identify the compounds and complete the chemical reaction using information supplied in the question.

Y has structure similar to benzene (inorganic benzene)

In Boric acid each B atom is s² hybridized
and contains units which are held together by hydrogen bonds.

The structure of borax is

The treatment of borides with acids produces boranes.

H₂B₄O₇

Boric acid is a tribasic acid

The structure of borax is

H₃BO₃ is a weak monobasic acid. It does not liberate H⁺ but accepts OH⁻, i.e. it is Lewis acid.

BF₃ is a gaseous substance.