Discuss the pattern of variation in the oxidation states of (i) B to Tl and (ii) C to Pb.

How can you explain higher stability of BCl3 as compared to TlCl3?

Why does boron trifluoride behave as a Lewis acid?

Consider the compounds, BCl3 and CCl4. How will they behave with water? Justify.

Is boric acid a protic acid? Explain.

Explain what happens when boric acid is heated.

4Describe the shapes of BF₃ and BH ^–. Assign the hybridisation of boron in these species. 4

Write reactions to justify amphoteric nature of aluminium.

What are electron deficient compounds? Are BCl₃ and SiCl₄ electron deficient species? Explain.

Write the resonancestructuresofand.

What is the state of hybridisation of carbon in (a) (b) diamond (c) graphite?

Explain the difference in properties of diamond and graphite on the basis of their structures.

Rationalise the given statements and give chemical reactions: (I) Lead(II) chloride reacts with Cl₂ to givePbCl₄. (II) Lead(IV) chloride is highly unstable towardsheat. (III) Lead is known not to form an iodide, PbI₄.

Suggest reasons why the B–F bond lengths in BF3 (130 pm) and (143 pm) differ.

If B–Cl bond has a dipole moment, explain why BCl3 molecule has zero dipole moment.

Aluminium trifluoride is insoluble in anhydrous HF but dissolves on addition of NaF. Aluminium trifluoride precipitates out of the resulting solution when gaseous BF₃ is bubbled through. Give reasons.

Suggest a reason as to why CO is poisonous.

How is excessive content of CO2 responsible for global warming?

Explain structures of diborane and boric acid.

What happens when (I) Borax is heatedstrongly, (II) Boric acid is added towater, (III) Aluminium is treated with diluteNaOH, (IV) BF₃ is reacted withammonia?

Explain the following reactions (I) Silicon is heated with methyl chloride at high temperature in the presence ofcopper; (II) Silicon dioxide is treated with hydrogenfluoride; (III) CO is heated withZnO; (IV) Hydrated alumina is treated with aqueous NaOHsolution.

Give reasons: (I) Conc. HNO₃ can be transported in aluminiumcontainer. (II) A mixture of dilute NaOH and aluminium pieces is used to opendrain. (III) Graphite is used aslubricant. (IV) Diamond is used as anabrasive. (V) Aluminium alloys are used to make aircraftbody. (VI) Aluminium utensils should not be kept in waterovernight. (VII) Aluminium wire is used to make transmissioncables.

Explain why is there a phenomenal decrease in ionisation enthalpy from carbon to silicon?

How would you explain the lower atomic radius of Ga as compared to Al?

What are allotropes? Sketch the structure of two allotropes of carbon namely diamond and graphite. What is the impact of structure on physical properties of two allotropes?

(I) Classify following oxides as neutral, acidic, basic oramphoteric: CO, B₂O₃, SiO₂, CO₂, Al₂O₃, PbO₂, Tl₂O₃ (II) Write suitable chemical equations to show theirnature.

In some of the reactions thallium resembles aluminium, whereas in others it resembles with group I metals. Support this statement by giving some evidences.

When metal X is treated with sodium hydroxide, a white precipitate (A) is obtained, which is soluble in excess of NaOH to give soluble complex (B). Compound (A) is soluble in dilute HCl to form compound (C). The compound (A) when heated strongly gives (D), which is used to extract metal. Identify (X), (A), (B), (C) and (D). Write suitable equations to support theiridentities.

What do you understand by (a) inert pair effect (b) allotropy and (c) catenation?

A certain salt X, gives the following results. (I) Its aqueous solution is alkaline tolitmus. (II) It swells up to a glassy material Y on strongheating. (III) Whenconc.H₂SO₄isaddedtoahotsolutionofX,whitecrystalofanacidZ separates out.Write equations for all the above reactions and identify X, Y and Z.

Write balanced equations for: (I) BF₃ + LiH? (II) B₂H₆ + H₂O? (III) NaH + B₂H₆? (IV) H₃BO₃ (V) Al + NaOH? (VI) B₂H₆ + NH₃?

Give one method for industrial preparation and one for laboratory preparation of CO and CO₂ each.

An aqueous solution of borax is (a) neutral (b) amphoteric(c) basic (d) acidic

Boric acid is polymeric due to (a) its acidic nature (b) the presence of hydrogen bonds(c) its monobasic nature (d) its geometry

The type of hybridisation of boron in diborane is (a) sp (b) sp² (c) sp³ (d) dsp²

Thermodynamically the most stable form of carbon is (a) diamond (b) graphite(c) fullerenes (d) coal

Elements of group 14 (I) exhibit oxidation state of +4only (II) exhibit oxidation state of +2 and+4 (III) form M^2– and M⁴⁺ion (IV) form M2+ and M4+ ions

If the starting material for the manufacture of silicones is RSiCl₃, write the structure of the product formed.