Why do boron halides form addition compounds with NH3?
Boron halides are lewis acids and can accept a pair of electrons from amines to form addition product.
A certain salt X, gives the following results.
(i) Its aqueous solution is alkaline to litmus.
(ii) It swells up to a glassy material Y on strong heating.
(iii) When cone.H2SO4is added to a hot solution of X, white crystal of an acid Z separates out.
Boric acid is an acid because its molecule
(a) contains replaceable H+ ion
(b) gives up a proton.
(c)accepts OH–from water releasing proton.
(d) combines with proton from water molecule.
Ionisation enthalpy (∆ tH1 kJ mol-1) for the elements of Group 13 follows the order.
(a) B > A1 > Ga > In > T1
(b) B < A1 < Ga< In
(d) B > A1 < Ga > In < T1
The reason for small radius of Ga compared to Al is_________ .
(a) poor screening effect of d and f orbitals
(b) increase in nuclear charge
(c) presence of higher orbitals
(d) higher atomic number
Which of the following statements are correct?
(a) Fullerenes have dangling bonds.
(b) Fullerenes are cage-like molecules.
(c) Graphite is thermodynamically most stable allotrope of carbon.
(d) Graphite is slippery and hard and therefore used as a dry lubricant in
Elements of group 14
(a) exhibit oxidation state of +4 only (b) exhibit oxidation state of +2 and +4
(c) form M2-and M4+ ion (d) form M2+ and M4+ ions.
Give the chemical reactions as an evidence for each of the following observations.
(i) Tin (II) is a reducing agent whereas lead (II) is not.
(ii) Gallium (I) undergoes disproportionation reaction.
In the structure of diborane
(a) all hydrogen atoms lie in one plane and boron atoms lie in a plane perpendicular to this plane.
(b) 2 boron atoms and 4 terminal hydrogen atoms lie in the same plane and 2 bridging hydrogen atoms lie in the perpendicular plane.
(c) 4 bridging hydrogen atoms and boron atoms lie in one plane and two terminal hydrogen atoms lie in a plane perpendicular to this plane.
(d) all the atoms are in the same plane.
Boric acid is polymeric due to
(a) its acidic nature (b) the presence of hydrogen bonds
(c) its monobasic nature (d) its geometry
Explain the following:
(i) C02 is a gas whereas Si02 is a solid.
(b) Silicon forms SiF62- ion whereas corresponding fluoro compound of carbon is not known.
Assertion (A): If aluminium atoms replace a few silicon atoms in three dimensional network of silicon dioxide, the overall structure acquires a negative charge.
Reason (R): Aluminium is trivalent while silicon is tetravalent.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) Both A and R are not correct.
(d) A is not correct but R is correct.
What is meant by catenation? Why does ‘C show the property of catenation to maximum extent?
Aluminium dissolves in mineral acids and aqueous alkalies and thus shows amphoteric character, A piece of aluminium foil is treated with dilute hydrochloric acid or dilute sodium hydroxide solution in a test tube and on bringing a burning matchstick near the mouth of the test tube, a pop sound indicates the evolution of hydrogen gas. The same activity when performed with concentrated nitric acid, reaction doesn't proceed. Explain the reason.
Match the species given in Column I with the hybridisation given in Column II.
| Column I | Column II |
| (i) Boron in [B(OH)4]" | (a) sp2 |
| (ii) Aluminium in [A1(H20)6]3+ | (b) sp3 |
| (iii) Boron in B2H6 | (c) sp3d2 |
| (iv) Carbon in Buckminsterfullerene | |
| (v) Silicon in SiO44- | |
| (vi) Germanium in [GeCl6]2- |
In some of the reactions thallium resembles aluminium, whereas in others it resembles with group 1 metals. Support this statement by giving some evidences.
Give the chemical reaction as an evidence for each of the following observations.
(i) Tin (II) is a reducing agent whereas lead (II) is not.
(ii) Gallium (I) undergoes disproportionation reaction.
Silicon has a strong tendency to form polymers like silicones. The chain length of silicone polymer can be controlled by adding f (a) MeSiCl3 (b) Me2SiCl2 (c) Me3SiCl (d) Me4Si
Which of the following statements are correct? Answer on the basis of figure.
(a) The two bridged hydrogen atoms and the two boron atoms lie in one plane.
(b) Out of six B – H, bonds two bonds can be described in terms of 3 centre 2-electron bonds.
(c) Out of six B – H bonds four B – H bonds can be described in terms of 3 centre 2 electron bonds.
(d) The four terminal B – H bonds are two centre-two electron regular bonds.
Give reasons for the following:
(a) CCl4 is immiscible in water, whereas SiCl4 is easily hydrolysed.
(b) Carbon has a strong tendency for catenation compared to silicon.
Describe the shapes of BF3 and BH4–. Assign the hybridisation of boron in these species.
What are electron deficient compounds? Are BCl3 and SiCl4 electron deficient species? Explain.
Give one method for industrial preparation and one for laboratory preparation of CO and C02 each.
Thermodynamically the most stable form of carbon is
(a)diamond (b) graphite (c) fullerenes (d) coal
What happens when
(i) Quick lime is heated with coke?
(ii) Carbon monoxide reacts with Cl2?
Give reasons:
(a) Why do Boron halides form addition compound with NH3?
(b) The tendency for catenation decreases down the group in Group 14.
(c) PbO2 is a stronger oxidising agent than SnO2.
(a) Why do Boron halides form addition compound with NH3?
(b) Assign appropriate reason for each of the following observations:-
(i) Anhydrous AlCl3 is used as a catalyst in many organic reactions.
(ii) No form of elemental silicon is comparable to graphite.