In silica (SiO₂), each silicon atom is bonded to

• two oxygen atoms

• four oxygen atoms

• one silicon and two oxygen atoms

• one silicon and four oxygen atoms

C-C bond length is maximum in

• diamond

• graphite

• naphthalene

• fullerone

Dry ice is

• Solid H₂O

• Solid CO₂

• Solid N₂O₄

• Solid NH₃

274.

When borax is heated strongly, it gives

• BaBO₂

• B₂O₃

• B₃N₃H₆

• Na₂B₄O₇

Sindhur, an oxide of lead, is an example of ............. oxide.

• basic

• super

• mixed

• amphoteric

The magnetic nature of boron molecule is same as the magnetic nature of

• nitrogen molecule

• carbon molecule

• unipositive nitrogen molecule

• oxide ion

Which of the following is not a true alum?

• Na₂SO₄.Al₂(SO₄)₃.24H₂O

• MgSO₄.Cr₂(SO₄)₃.24H₂O

• K₂SO₄.Cr₂(SO₄)₃.24H₂O

• (NH₄)₂SO₄.Fe(SO₄)₃.24H₂O

The densities of graphite and diamond at 298 K are 2.25 and 3.31 g cm^-3 respectively. If the standard free energy difference is 1895 J mol^-1, the pressure at which graphite will be transformed into diamond is

• 9.92 × 10⁸ Pa

• 9.92 × 10⁷ Pa

• 9.92 × 10⁶ Pa

• None of these

Which one of the following elements does not form triiodide on reacting with iodine?

• B

• Ti

• Al

• Ga

An example of covalent solid is

• MgO

• Mg

• SiC

• CaF₂