NCERT Exemplar solutions for Chemistry [English] Class 11 chapter 11 - The p-block Elements [Latest edition]

The element which exists in liquid state for a wide range of temperature and can be used for measuring high temperature is ______.

Which of the following is a Lewis acid?

The geometry of a complex species can be understood from the knowledge of type of hybridisation of orbitals of central atom. The hybridisation of orbitals of central atom in [Be(OH)₄]^– and the geometry of the complex are respectively.

Which of the following oxides is acidic in nature?

The exhibition of highest co-ordination number depends on the availability of vacant orbitals in the central atom. Which of the following elements is not likely to act as central atom in \[\ce{MF^{3-}6}\]?

Boric acid is an acid because its molecule ______.

Catenation i.e., linking of similar atoms depends on size and electronic configuration of atoms. The tendency of catenation in Group 14 elements follows the order:

Silicon has a strong tendency to form polymers like silicones. The chain length of silicone polymer can be controlled by adding ______.

Ionisation enthalpy (∆_iH₁kJ mol^–1) for the elements of Group 13 follows the order.

In the structure of diborane ______.

A compound X, of boron reacts with NH₃ on heating to give another compound Y which is called inorganic benzene. The compound X can be prepared by treating BF₃ with Lithium aluminium hydride. The compounds X and Y are represented by the formulas.

Quartz is extensively used as a piezoelectric material, it contains ______.

The most commonly used reducing agent is ______.

Dry ice is ______.

Cement, the important building material is a mixture of oxides of several elements. Besides calcium, iron and sulphur, oxides of elements of which of the group (s) are present in the mixture?

The reason for small radius of Ga compared to Al is:

(i) poor screening effect of d and f orbitals.

(ii) increase in nuclear charge.

(iii) presence of higher orbitals.

(iv) higher atomic number.

The linear shape of CO₂ is due to:

(i) sp³ hybridisation of carbon.

(ii) sp hybridisation of carbon.

(iii) pπ – pπ bonding between carbon and oxygen.

(iv) sp² hybridisation of carbon.

Me₃SiCl is used during polymerisation of organo silicones because:

(i) the chain length of organo silicone polymers can be controlled by adding Me₃SiCl.

(ii) Me₃SiCl blocks the end terminal of silicone polymer.

(iii) Me₃SiCl improves the quality and yield of the polymer.

(iv) Me₃SiCl acts as a catalyst during polymerisation.

Which of the following statements are correct?

(i) Fullerenes have dangling bonds.

(ii) Fullerenes are cage-like molecules.

(iii) Graphite is thermodynamically most stable allotrope of carbon.

(iv) Graphite is slippery and hard and therefore used as a dry lubricant in machines.

Which of the following statements are correct. Answer on the basis of Figure.

(i) The two birdged hydrogen atoms and the two boron atoms lie in one plane;

(ii) Out of six B – H bonds two bonds can be described in terms of 3 centre 2-electron bonds.

(iii) Out of six B – H bonds four B – H bonds can be described in terms of 3 centre 2 electron bonds;

(iv) The four-terminal B – H bonds are two centre-two electron regular bonds.

Identify the correct resonance structures of carbon dioxide from the ones given below:

(i) O – C ≡ O

(ii) O = C = O

(iii) ^–O ≡ C – O⁺

(iv) ^–O – C ≡ O⁺

Draw the structures of BCl₃.NH₃ and AlCl₃ (dimer).

Explain the nature of boric acid as a Lewis acid in water.

Draw the structure of boric acid showing hydrogen bonding. Which species is present in water? What is the hybridisation of boron in this species?

Explain why the following compounds behave as Lewis acids?

BCl₃

Explain why the following compounds behave as Lewis acids?

AlCl₃

Give reasons for the following:

CCl₄ is immiscible in water, whereas SiCl₄ is easily hydrolysed.

Explain the following:

Silicon forms \[\ce{SiF^{2-}6}\] ion whereas corresponding fluoro compound of carbon is not known.

Explain the following:

CO₂ is a gas whereas SiO₂ is a solid.

Explain the following:

Silicon forms \[\ce{SiF^{2-}6}\] ion whereas corresponding fluoro compound of carbon is not known.

The +1 oxidation state in group 13 and +2 oxidation state in group 14 becomes more and more stable with increasing atomic number. Explain.

Carbon and silicon both belong to the group 14, but inspite of the stoichiometric similarity, the dioxides, (i.e., carbon dioxide and silicon dioxide), differ in their structures. Comment.

If a trivalent atom replaces a few silicon atoms in three-dimensional network of silicon dioxide, what would be the type of charge on overall structure?

When BCl₃ is treated with water, it hydrolyses and forms [B[OH]₄]^– only whereas AlCl₃ in acidified aqueous solution forms [Al(H₂O)₆]³⁺ ion. Explain what is the hybridisation of boron and aluminium in these species?

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.

Explain the following:

Gallium has higher ionisation enthalpy than aluminium.

Explain the following:

Boron does not exist as B³⁺ ion.

Explain the following:

Aluminium forms [AlF₆]^3– ion but boron does not form [BF₆]^3– ion.

Explain the following:

PbX₂ is more stable than PbX₄.

Explain the following:

Pb⁴⁺ acts as an oxidising agent but Sn²⁺ acts as a reducing agent.

Explain the following:

Electron gain enthalpy of chlorine is more negative as compared to fluorine.

Explain the following:

Tl (NO₃)₃ acts as an oxidising agent.

Explain the following:

Carbon shows catenation property but lead does not.

Explain the following:

BF₃ does not hydrolyse.

Explain the following:

Why does the element silicon, not form a graphite like structure whereas carbon does.

Identify the compounds A, X and Z in the following reactions:

\[\ce{A + 2HCl + 5H2O -> 2NaCl + X}\]

Identify the compounds A, X and Z in the following reactions:

\[\ce{X ->[Δ][370 K] HBO2 ->[Δ][> 370 K] Z}\]

Complete the following chemical equations:

\[\ce{Z + 3 LiAlH4 -> X + 3LiF + 3AlF_3}\]

\[\ce{X + 6H2 -> Y + 6H2}\]

\[\ce{3X + 3O2 ->[Δ] B2O3 + 3H2O}\]

Match the species given in Column I with the properties mentioned in Column II.

Match the species given in Column I with properties given in Column II.

Match the species given in Column I with the hybridisation given in Column II.

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.

Assertion (A): Silicons are water repelling in nature.

Reason (R): Silicons are organosilicon polymers, which have (–R₂SiO–) as repeating unit.

Describe the general trends in the following properties of the elements in Groups 13 and 14.

Atomic size

Describe the general trends in the following properties of the elements in Groups 13 and 14.

Ionisation enthalpy

Describe the general trends in the following properties of the elements in Groups 13 and 14.

Metallic character

Describe the general trends in the following properties of the elements in Groups 13 and 14.

Oxidation states

Describe the general trends in the following properties of the elements in Groups 13 and 14.

Nature of halides

Account for the following observations:

AlCl₃ is a Lewis acid

Account for the following observations:

Though fluorine is more electronegative than chlorine yet BF₃ is a weaker Lewis acid than BCl₃ 

Account for the following observations:

PbO₂ is a stronger oxidising agent than SnO₂ 

Account for the following observations:

The +1 oxidation state of thallium is more stable than its +3 state.

When aqueous solution of borax is acidified with hydrochloric acid, a white crystalline solid is formed which is soapy to touch. Is this solid acidic or basic in nature? Explain.

Three pairs of compounds are given below. Identify that compound in each of the pairs which has group 13 element in more stable oxidation state. Give reason for your choice. State the nature of bonding also.

TlCl₃, TlCl

Three pairs of compounds are given below. Identify that compound in each of the pairs which has group 13 element in more stable oxidation state. Give reason for your choice. State the nature of bonding also.

AlCl₃ , AlCl

Three pairs of compounds are given below. Identify that compound in each of the pairs which has group 13 element in more stable oxidation state. Give reason for your choice. State the nature of bonding also.

InCl₃, InCl

BCl₃ exists as monomer whereas AlCl₃ is dimerised through halogen bridging. Give reason. Explain the structure of the dimer of AlCl₃ also.

Boron fluoride exists as BF₃ but boron hydride doesn’t exist as BH₃. Give reason. In which form does it exist? Explain its structure.

What are silicones? State the uses of silicones.

What are boranes? Give chemical equation for the preparation of diborane.

A compound (A) of boron reacts with NMe₃ to give an adduct (B) which on hydrolysis gives a compound (C) and hydrogen gas. Compound (C) is an acid. Identify the compounds A, B and C. Give the reactions involved.

A nonmetallic element of group 13, used in making bullet proof vests is extremely hard solid of black colour. It can exist in many allotropic forms and has unusually high melting point. Its trifluoride acts as Lewis acid towards ammonia. The element exihibits maximum covalency of four. Identify the element and write the reaction of its trifluoride with ammonia. Explain why does the trifluoride act as a Lewis acid.

A tetravalent element forms monoxide and dioxide with oxygen. When air is passed over heated element (1273 K), producer gas is obtained. Monoxide of the element is a powerful reducing agent and reduces ferric oxide to iron. Identify the element and write formulas of its monoxide and dioxide. Write chemical equations for the formation of producer gas and reduction of ferric oxide with the monoxide.