NCERT Class 11 Chemistry Chapter 11 Some P Block Elements Very Short Answer Questions

NCERT Solutions For Class 11 Chemistry Chapter 11 Some P Block Elements Very Short Question And Answers

Question 1. Name one ore of boron and give its formula.
Answer: Colemanite (Ca₂B₆O₁₁-5H₂O).

Question 2. What are the two isotopes present in natural boron?
Answer: (19.6%) and 1gB‘(80.4%).

Question 3. Which element of group 13 has the most stable +1 oxidation state?
Answer: Thallium (Tl) has the most stable +1 oxidation state because of its prominent inert pair effect.

Question 4. Which elements of Gr-13 form amphoteric hydroxide?
Answer: Al and Ga form amphoteric hydroxide

Read and Learn More NCERT Class 11 Chemistry Very Short Answer Questions

Question 5. Which element of group-13 forms only covalent compounds and why?
Answer:

Because of its small atomic size and high value of the sum of the first three ionisation enthalpies (Δ_iH₁ + Δ_iH₂ + Δ_iH₃), boron forms only covalent compounds.

Question 6. Give the general valence shell electronic configuration of group-13 elements. What is their common oxidation state?
Answer: ns²np¹; + 3 (where n = 2 to 6).

Question 7. Which one among group-13 elements has the highest value of ionisation enthalpy?
Answer: Boron.

Question 8. Which element of Gr-13 is the most abundant one?
Answer: Aluminium.

Question 9. Write one physical characteristic of boron in which it differs from the other members of group 13.
Answer: Boron is a non-metal, while other elements of group 13 are metals.

Question 10. Why boron compounds such as BF₃ are called electron-deficient compounds?
Answer: Because the valence shell of B in BF₃ has only six elections. Two more electrons are required to complete the octet.

Question 11. Which of the Gr-13 elements forms acidic oxide?
Answer: Boron forms acidic oxide.

Question 12. Arrange the following compounds in order of decreasing strength as Lewis acid: BCl₃, BBr₃, BF₃
Answer:

BBr₃ > BCl₃ > BF₃ .

Question 13. Which compound is responsible for the green-edged Oame in a test for borate ion?
Answer: Triethyl borate [B(OC₂H₅)₃].

Question 14. Name the compound which on warming produces pure BF3
Answer: Benzenediazonium fluoroborate \(\left(\mathrm{C}_6 \mathrm{H}_5 \stackrel{+}{\mathrm{N}}_2 \mathrm{BF}_4^{-}\right)\)

Question 15. Explain why BF| has no existence.
Answer: This is because boron cannot extend its valency to six due to the absence of vacant d -d-orbitals

Question 16. What type of cations are identified by the borax bead test
Answer: Cations that show colour are identified by the borax bead test

Example: CO^-2+, Ni²⁺, etc

Question 17. What happens when the borax solution is acidified? sp³ -hybridised.
Answer: Boric acid is obtained when the borax solution is acidified (Na₂B₄O₇ + 2HCl + 5H₂O→2NaCl + 4H₃BO₃).

Question 18. How are the BO^3-₃ units in boric acid linked to give 12 icosahedral units, it is an extremely hard solid. Layered structure?
Answer:

BO^3-₃ units are linked through hydrogen bonding

Question 19. What is the shape of BO^3-₃ion?
Answer: Trigonal planar because the central B -atom is sp² – hybridised

Question 20. Which compounds are formed on heating boric acid?
Answer:  HBO₂, H₂B₄O₇ and B₂O₃ Using a balanced chemical equation show how B(OH)₃ behaves as a monobasic acid in water.

Question 21. Using a balanced chemical equation show how B(OH)₃ behaves as a monobasic acid in water.
Answer: B(OH)₃ + H₂O->[B(OH)₄] +H⁺. As it produces one free H+ ion in solution, it behaves as a monobasic acid

Question 22. What are the forces involved between the layers of two-dimensional sheets of H₃BO₃?
Answer: Weak van der Waals forces

Question 23. What is the composition of the transparent glassy bead obtained on heating borax
Answer: (NaBO₂+ B₂O₃)

Question 24. What is the structural unit present in all allotropic forms of boron?
Answer: B₁₂ icosahedral units

Question 25. What type of bonds are
Answer: Purely covalent B — H bonds and three-centred two-electron (3c-2e) B…H…..B bridge bonds. present in B2Hg molecule?

Question 26. Explain why boron cannot form B3+ ions
Answer:

This is because of its very small atomic size and large sum ofthe first three ionisation enthalpies.

Question 27. Mention the states of hybridisation of boron in B₂H₆ and BF₃
Answer:

In B₂H₆ , boron is sp³ -hybridised while in BF₃ , boron is sp² -hybridised

Question 28. Crystalline boron is an extremely hard solid why?
Answer:

Because the dimensional network structure involves B₁₂ icosahedral units, it is an extremely hard solid

Question 29. What are boranes?
Answer:

Stable covalent boron hydrides such as B₂H₆, B₄H₁₀, B₅H₉ etc. in analogy with alkanes are called boranes

Question 30. Two out of five members of the carbon family are distinctly metals
Answer: Sn and Pb are distinctly metals.

Question 31. Wlilch one out of catechol, resorcinol and quinol can be used to titrate boric acid against sodium hydroxide using methyl orange as the indicator.
Answer: Two  OH groups are present at adjacent ring carbons due to which it can form a stable complex with B(OH)^–₄.

Question 32. Carbon forms covalent compounds but lead forms ionic compounds—Why?
Answer:

The ionisation enthalpy of carbon is much higher (1086 kJ-mol-1)whereas that of lead is much lower (715 kJ-mol^-1). Because of this, carbon forms covalent compounds but lead forms ionic compounds.

Question 33. Which element of the carbon family has no d-orbital in Its valence shell?
Answer:

Carbon has no d -d-orbital in its valence shell.

Question 34. Among the group-14 elements which is the most electronegative one?
Answer: Carbon is the most electronegative one.

Question 35. Which member of the carbon family has the lowest melting point?
Answer: Tin has the lowest melting point.

Question 36. Out of diamond & graphite which is a good conductors of electricity and which is a good conductor of heat
Answer:

Graphite is a good conductor of electricity, while diamond is a good conductor of heat.

Question 37. Which member of the carbon family has the highest value of first ionisation enthalpy?
Answer: The first ionisation enthalpy value of carbon is the highest.

Question 38. Which member of the carbon family has the maximum tendency to exhibit catenation property?
Answer: Carbon has a maximum tendency to exhibit catenation.

Question 39. What are the structural units of ice and dry ice?
Answer: H₂O and CO₂ respectively

Question 40. Among the group-14 elements which one exhibits pπ-pπ multiple bond
Answer:  Carbon exhibits pπ-pπ multiple bonds.

Question 41. What is the basic building unit of all silicates?
Answer:  SiO₄^4- is the basic building unit of all silicates.

Question 42. What happens when cone. H₂SO₄ is dropped on sugar?
Answer: Sugar charcoal is formed.’

Question 43. What is buckminsterfullerene?
Answer: The C₆O fullerene is known as buckminsterfullerene.

Question 44. What is the state of hybridisation of carbon in
Answer:

1. sp²
2. sp²
3. sp.

Question 45. Which allotrope of C is used as a moderator in atomic reactors and as a solid lubricant for heavy machinery?
Answer: Graphite

Question 46. Mention the oxides of C which are the anhydrides of carbonic acid and formic acid respectively.’
Answer: CO₂ is the anhydride of carbonic acid, while CO is the anhydride of formic acid.

Question 47. Name the gases which are present in producer gas
Answer: Carbon monoxide and nitrogen

Question 48. Out of CO and CO₂ which acts as a ligand and can form a coordinate bond with certain metals why?
Answer:

Due to the presence of a lone pair of electrons on carbon, CO acts as a ligand and forms a coordinate bond with certain metals

Question 49. What is the state of hybridisation of carbon in each of the following:

1. Diamond
2. Graphite
3. Fullerene

Answer:

1. sp³
2. sp²
3. sp

Question 50. What is carborundum?
Answer: Silicon carbide (SiC) is called carborundum.

Question 51. Give an example of a reaction where CO₂  acts as an oxidising agent
Answer:

Question 52. What are zeolites?
Answer: Zeolites are microporous 3D aluminosilicates

Question 53. Write the name of the compound used as a fire extinguisher under the name pyrene.
Answer: Carbon tetrachloride (CCl₄)

Question 54. Name the hardest compound of boron
Answer: Boron carbide or morbid.

Question 55. What is alone?
Answer: Alane is a polymeric hydride form of aluminium with the formula (AlH₃)_n

Question 56. Which two elements of group 13 form amphoteric hydroxides?
Answer: Al and Ga

Question 57.  What are the two stable natural isotopes of boron?
Answer: ¹¹B and ¹⁰B

Question 58. Which of the group-13 elements has the most stable +1 oxidation state?
Answer: TI

Question  59. Which of the Gr-13 elements forms only covalent compounds?
Answer:  Boron

Question 60.  The melting point of boron is very high, even though it is a non-metal—why
Answer: Because B exists as a giant covalent molecule,

Question 61. Which acid is obtained when an aqueous solution of borax is acidified?
Answer: Boric acid (H₃BO₃)

Question 62. Which are called boranes?
Answer:  Covalent boron hydrides,

Question 63. What is the correct structural formula of borax?
Answer: Na₂[B₄O₅(OH)₄].8H₂O

Question 64. What happens when orthoboric acid is heated till red hot?
Answer: At first HBO₂ then , H₂B₄O₇ and finally B₂O₃ forms,

Question 65. What is inorganic benzene? Why is it called so?
Answer: Borazine (B₃N₃H₆), because of structural similarity with benzene

Question 66. What is the common oxidation state of group-13 elements?
Answer: +3

Question 67. Write down the chemical composition of the coloured compound obtained finally in the borax bead test.
Answer: Metal metaborate, MBO₂ or M'(BO₂)₂ or M”(BO₂)₃ [M = monovalent, M’ = divalent, M”= trivalent ),

Question 68. Arrange boron halides in decreasing strength as Lewis acid.
Answer: BI₃ > BBr₃ > BCl₃ > BF₃ ,

Question 69. How can boric acid form polymer?
Answer: By formation of hydrogen bonding

Question 70. Explain why BF^-6₃ does not exist.
Answer: Because boron has no vacant d -d-orbital,

Question 71. What is duralumin? Mention its uses.
Answer: It is an alloy of aluminium; it is used for making aeroplanes, automobile parts, pressure cookers etc.

Question 72. Borazine is more reactive than benzene—why?
Answer:  The C =C bonds in benzene are non-polar but the B — N bonds in borazine are polar

Question 73. Some metals are extracted from their oxides by reducing with aluminium instead of carbon—why?
Answer: Because they form metal carbides,

Question 74. Which out of CCl₄ and SiCl₄ reacts with water and why?
Answer: SiCl₄, because there are vacant d orbitals in the valence shell of silicon

Question 75. What is water gas?
Answer: Equimolar mixture of CO and H

Question 76. Carbon compounds are relatively less reactive—why?
Answer: Because of the much higher bond dissociation enthalpy of the C— C bond

Question 77. What is the value of the dipole moment of carbon suboxide and why?
Answer:

Question 78. Mention the hybridisation state of carbon in CO^-2₃ and CO₂.
Answer: sp² and sp respectively

Question 79. Write the name of a neutral oxide of carbon.
Answer: Carbon Monoxide (CO)

Question 80. What is dry ice?
Answer: Solid carbon dioxide,

Question 81. What is the basic structural unit of silicates?
Answer: SiO

Question 82. Write the general formula of silicones.
Answer:

Question 83. Explain why the compounds of boron are called electron-deficient compounds.
Answer: Boron contains six valence electrons, i.e., its octet is incomplete

Question 84. Explain why BF₃ forms an addition compound with NH₃.
Answer:

For completing its octet the boron atom in BF3 accepts a pair of electrons from the nitrogen atom of ammonia and as a result, an addition compound is obtained.

Question 85. Out of InCl₃ and In Cl, which one is more stable and why?
Answer:

Due to the weak inert pair effect, the +3 oxidation state of In is relatively more stable

Question 86. Explain why boron does not form BF₆^3- ion
Answer:

The boron atom does not have a vacant d -d-orbital. Hence, it cannot expand its coordination up to six.

Question 87. Metallic aluminium is frequently used as a reducing agent in the extraction of Cr, Mn, Fe etc —why?
Answer:

Because of the much higher affinity of Al for oxygen, Al eliminates oxygen from the oxides of moderately electropositive metals,

Question 88. What is called the mixture containing 95% O₂ and 5% CO₂
Answer: Carbogen,

Question 89. What is the purest allotropic form of amorphous carbon?
Answer: Lamp black,

Question 90. What is the molecular mass of the most available natural fullerene?
Answer: 2HO, (C₆₀fullerene) ,

Question 91. Write the names of two greenhouse gases.
Answer: Carbon dioxide and methane,

Question 92. What is ivory black?
Answer: The black substance obtained on dissolution of Ca-salts present in bone charcoal with HCl,

Question 93. Which out of carbon and silicon forms multiple bonds and why?
Answer: Carbon having a small atomic size and high electronegativity can form multiple bonds by pπ-pπ overlapping,

Question 94. What is the anion present in phyllosilicates
Answer: Si₂O^6-₇

Question 95. Why is orthoboric acid used in talcum powders?
Answer:  Orthoboric acid is a fine white powder that easily mixes with talcum powders and imparts antiseptic properties.

Question 96. Why molten AlBr₃ is a poor conductor of electricity?
Answer:  AlBr₃ is a covalent molecule. As it ionises to a very small extent even in a molten state, it is a poor conductor of electricity.

Question 97. Which glass has the highest percentage of lead? Mention its use.
Answer: Flint glass contains the highest percentage of lead as lead silicate. It is used for optical purposes.

Question 98. Carbon exhibits catenation property but lead does not— why?
Answer: The C— C bond dissociation enthalpy is much higher than the Pb —Pb bond dissociation enthalpy

Question 99. Which are called methanides?
Answer: The carbides containing C₄– ions are called methanides;

Question 100. (CH₃)₃SiOH is more acidic than (CH₃)₃COH, even though carbon is more electronegative than silicon— explain
Answer: Because of d-orbital resonance, the conjugate base of (CH₃)₃SiOH is relatively more stable

Question 101. Silicon is unable to form structures like graphite—why?
Answer: Due to the larger size and lower electronegativity of Si as compared to C, silicon can’t form double bonds through sp² -hybridisation

Question 102. Mention one property of fullerene which differs from that of diamond and graphite.
Answer: Fullerenes dissolve in organic solvents while diamond or graphite does not

Question 103. Write the formula of the following ore: bauxite
Answer: Al₂O₃-2H₂O

Question 104. A white precipitate is formed when a small amount of a gas is passed through lime water. The precipitate dissolves when excess ofthe gas is passed. What can be the possible gases? How would you identify the gases?
Answer:  The possible gases may be either carbon dioxide or sulphur dioxide

Question 105. Which one is the hardest allotrope of carbon? Answer with reason
Answer: Diamond

Question 106. Write balanced equations for Al + NaOH →
Answer:

2Al + 2NaOH + 6H₂O → 2Na+[Al(OH)₄]^–+ 3H₂

Question 107. What are aquadag and oildag? Mention their uses.
Answer:

A colloidal solution of graphite in water is known as aquadag and a colloidal solution of graphite in oil is known as oildag. These are used as lubricants.

NCERT Solutions For Class 11 Chemistry Chapter 11 Some P Block Elements Fill In The Blanks

Question 1. Boric acid is a ________________ acid and not an acid
Answer: Lewis, protonic

Question 2. Due to _____________ Tl⁺ ion is more stable than Tl³⁺ ion.
Answer: Inert pair effect,

Question 3. Two types of bonds in diborane are covalent and ___________ bond
Answer: 3c-2e bridge bond,

Question 4. Tl³⁺ ion acts as __________________ agent.
Answer: Oxidising,

Question 5. AlCl₃ is a __________________ Lweis acid than BCl
Answer: Stronger

Question 6. BCl₃ is a__________________ Lweis acid than BF
Answer: Stronger

Question 7. AlF₃ is an __________________compound, but AlCl is a __________________compound
Answer: Ionic, covalent

Question 8. The hydrides of boron are called__________________
Answer: Boranes,

Question 9. Inorganic benzene is chemically known as __________________
Answer: Borazine

Question 10. Anhydrous aluminium chloride exists as a __________________
Answer: Dimer

Question 11. The B—F bond present in BF₃ is __________________ compared to the B — F bond present in BF₄.
Answer: Shorter

Question 12. When H3B03 is strongly heated __________________ obtained
Answer: BO (Boron Trioxide)

Question 13. BN is a crystalline solid having a structure similar to __________________
Answer: Graphite

Question 14. On moving down the group, the stability of the +1 oxidation state of the members of the boron family +3 oxidation state
Answer: Increases And Decreases

Question 15. Except boron all members of boron family are_______________
Answer: Metals

Question 16. Except ______________ all members of the carbon family exhibit allotropy.
Answer: Lead

Question 17. Potassium ferrocyanide reacts with concentrated does not. Is used as a fuel. Sulphuric acid to form _____________ gas
Answer: CO

Question 18. SnCl₂ acts as a __________________
Answer: Reducing

Question 19. Out of CO and CO₂ __________________ combines with haemoglobin
Answer: CO

Question 20. Due to agent ________________ the +2 oxidation state of group 1 elements gradually becomes stable down the group.
Answer: Inert pair effect

Question 21. Only ________________ of the carbon family does not react with water.
Answer: Lead

Question 22. Carbides which on hydrolysis product CH₄ are called ________________
Answer: Methanides

Question 23. The hydrides of silicon are called ______________ is called ‘sugar of lead
Answer: Silanes(Si_nH_2n+2+ 2

Question 24. ________________ is called ‘sugar of lead
Answer: Pb(CH₃COO)₂

Question 25. Formic acid in dehydration produces
Answer: CO

Question 26. Due to the absence of a complex.
Answer: D orbital

Question 27. Mica is an example of
Answer: Sheet Silicate

Question 28. PbCl₄ exists bu ____________
Answer: PbI₄

Question 29. Out of CO and CO₂ ____________ is used as a fuel
Answer: CO

Question 30. Zircon (ZrSiO₄) is an example of _____________
Answer: Orthosilicate

Question 31. In silicones _________________ units are held by Si —O —Si
Answer: R₂SiO

Question 32. Asbestos ______________ is a silicate mineral existing in
Answer: Mg₃(Si₂O₅)(OH)₄