Reaction of diborane with ammonia gives initially :

• B₂H₆ . NH₃

• borazole

• B₂H₆ . 3NH₃

• [BH2(NH3)2]⁺ [BH₄]^-

Select the correct options from the following :

• Graphene is an atomic layer of graphite

• Graphene is an atomic layer composed of sp²-hybridised carbon.

• Chemical bonds in graphite are similar in strength to that of diamond.

• All of these.

143.

Many compounds are formed by carbon atom because of its :

• more reactivity

• covalent and ionic nature

• variable valency

• catenation nature

Addition of group-13 elements to intrinsic semiconductors results in

• creation of conduction band slightly above the valence band

• creation of conduction band slightly below the valence band

• creation of valence band slightly above the conduction band.

• overlapping of valence band and conduction band

Which of the following elements will have the highest electron affinity ?

• Chlorine

• Nitrogen

• Phosphorus

• Fluorine

Assertion: Conductivity of silicon increases by doping it with group-15 elements.

Reason : Doping means introduction of small amount of impurities like P, As or Bi into the pure crystal.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

For silicon which is not correct?

• It is a type of silicate.

• It is thermally unstable.

• It is hydrophilic.

• Repeating unit is R₂SiO.

If Si is doped with B,

• n-type semiconductor is formed

• p-type semiconductor is formed

• insulator is formed

• polymer is formed.

Iodine oxidises sodium borohydride to give

• B₂H₆

• sodium hydride

• HI

• I₃^-

The wrong statement about fullerene is

• it has 5-membered carbon ring

• it has 6-membered carbon ring

• it has sp² hybridization

• it has 5-membered rings more than 6-membered rings