CBSE Class 11 Chemistry HOTs The P Block Elements

Question. H₃BO₃ on heating up to 373 K yields
(a) boric anhydride
(b) orthoboric acid
(c) metaboric acid
(d) tetraboric acid
Answer : C

Question. In reaction BF₃ + 3LiBH₄ → 3LiF + X ; X is
(a) B₄H₁₀
(b) B₂H₆
(c) BH₃
(d) B₃H₈
Answer : B

Question. Soldiers of Napolean army while at alps during freezing winter suffered a serious problem as regards to the tin buttons of their uniforms. White metallic tin buttons got converted to grey powder. This transformation is related to
(a) a change in the partial pressure of oxygen in the air
(b) a change in the crystalline structure of tin 
(c) an interaction with nitrogen of the air at very low temperatures
(d) an interaction with water vapours contained in the humid air
Answer : B

Question. The dissolution of Al(OH)₃ by a solution of NaOH results in the formation of
(a) [Al(H₂O)₄ (OH)^]2+
(b) [Al(H₂O)₂ (OH)₄]^-
(c) [Al(H₂O)₃(OH)₃]
(d) [Al(H₂O)₆ (OH)₃]
Answer : B

Question. When aluminium is heated in atomoshere of nitrogen it forms :
(a) AlN
(b) Al₂N
(c) Al₃N
(d) Al₂N₃
Answer : A

Question. The tendency of X in BX₃ (X = F, Cl, OMe, NMe) to form a p - bond with boron follows the order
(a) BCl₃ < BF₃ < B(OMe)₃ < B(NMe₂)₃
(b) BF₃ < BCl₃ < B(OMe)₃ < B(NMe2)3
(c) BCl₃ < B(NMe₂)₃ < B(OMe)₃ < BF₃
(d) BCl₃ < BF₃ < B(NMe₂)₃ < B(OMe)₃
Answer : A

Question. PbO₂ is obtained from
(a) the reaction of PbO with HCl
(b) thermal decomposition of Pb(NO₃)₂ at 200 °C
(c) the reaction of Pb₃O₄ with HNO₃
(d) the reaction of Pb with air at room temperature
Answer : C

Question. The role of fluorspar (CaF₂) which is added in small quantities in the electrolytic reduction of alumina dissolved in fused cryolite (Na₃AlF₆) is
(a) as a catalyst
(b) to make the fused mixture very conducting
(c) to increase the temperature of the melt.
(d) to decrease the rate of oxidation of carbon at the anode.
Answer : B

Question. Aluminium chloride exists as dimer, (Al₂Cl₆) in solid state as well as in solution of non-polar solvents such as benzene. When dissolved in water, it gives
(a) [Al(OH)₆]^3- +3HCl
(b) [Al(H₂O)₆]³⁺ + 3Cl^-
(c) Al³⁺ + 3Cl^-
(d) Al₂O₃+6HCl
Answer : B

Question. Diborane is prepared on large scale by

Answer : A

Question. Silicon dioxide is formed by the reaction of
(a) SiCl₄ + H₂O
(b) SiO₂ + HF
(c) SiO₂ + NaOH
(d) SiCl₄ + NaOH
Answer : A

Question. What is not correct about carbon monoxide ?
(a) Carbon in CO is sp hybridised and is linear molecule
(b) CO is a ligand because it has a lone pair of electrons on the carbon atom
(c) CO is the reducing agent in metallurgy of iron
(d) CO has the structure C = O
Answer : D

Question. The gas evolved on heating CaF₂ and SiO₂ with concentrated H₂SO₄, on hydrolysis gives a white gelatinous precipitate. The precipitate is
(a) hydrofluorosilicic acid
(b) silica gel
(c) silicic acid
(d) calciumfluorosilicate
Answer : D

Question. On heating Pb(NO₃)₂, the products formed are:
(a) PbO, N₂, O₂
(b) Pb (NO₂)2, O₂
(c) PbO, NO₂, O₂
(d) Pb, N₂, O₂
Answer : C

Question. An allotrope of carbon which exhibits only two types of C - C bond distance of 143.5 pm and 138.3 pm, is
(a) charcoal
(b) graphite
(c) diamond
(d) fullerene
Answer : D

Question. A solid element (symbol Y) conducts electricity and forms two chlorides YCl_n (colourless volatile liquid) and YCl_n-2 (a colourless solid).
To which one of the following groups of the periodic table does Y belong?
(a) 13
(b) 14
(c) 15
(d) 16
Answer : B

Question. The reducing power of divalent species decreases in the order
(a) Ge > Sn > Pb
(b) Sn > Ge > Pb
(c) Pb > Sn > Ge
(d) None of these
Answer : A

Question. SiF4 gets hydrolysed giving........
(a) SiO₂
(b) Si(OH)₂F₂
(c) H₂SiF₆
(d) Si(OH)₄
Answer : D

Question. The product of the following reaction are: 

(a) SiC and CO₂
(b) SiO and CO
(c) SiC and CO
(d) Si and CO
Answer : C

Numeric Value Answer

Question. In aluminates, the coordination number of Al is
Answer : 6

Question. In a molecule of C₆₀ Buckminsterfullerene, what is the sum of six-membered and five membered rings?
Answer : 32

Question. How many orbitals of boron are involved in hybridisation in B₂H₆?
Answer : 4

Question. What is the sum for the molecular masses of constituents of producer gas?
Answer : 56

Question. How many oxides of the following are nonamphoteric in nature? CO₂, SiO₂, SnO₂ and CaO
Answer : 3