CBSE Class 12 Chemistry The p Block Elements Notes and Questions

N₂ has unique ability to pπ‐pπ multiple bonds whereas the heavier of this group do not form pπ–pπ because there atomic orbitals are so large & diffuse that they cannot have effective overlapping.

Nitrogen exists as diatomic molecule with triple bond between the two atoms whereas other elements form single bonds in elemental state. N cannot form dπ‐pπ due to the non availibility of d‐orbitals whereas other elements can.

 

 PROPERTIES:‐

(i)conc. HNO3 is a strong oxidizing agent & attacks most metals gold & Pt.

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(ii)Cr & Al do not dissolve HNO3 because of the formation of a positive film of oxide on the surface.

(iii)it oxidises non metals like I2 to HNO3, C to CO2 , S to H2so4

(iv)brown ring tes is used to detect NO‐.

PHOSPHOROUS:‐

ALLOTROPIC FORMS: White , red α‐black &β‐black . White phosphorous is more reactive red phosphorous because white P exists as discrete P4 molecules . in red P several P4molecules are linked to formed polymeric chain.

 

 

Question. Which of the following has the highest dipole moment?
(a) SbH₃
(b) AsH₃
(c) NH₃
(d) PH₃ 

Question. The basic character of hydrides of the V group elements decreases in the order
(a) NH₃ > PH₃ > AsH₃ > SbH₃
(b) SbH₃ > AsH₃ > PH₃ > NH₃
(c) SbH₃ > PH₃ > AsH₃ > NH₃
(d) NH₃ > SbH₃ > PH₃ > AsH₃ 

Question. Among the following oxides, the lowest acidic is
(a) As4O₆
(b) As4O₁₀
(c) P₄O₆
(d) P₄O₁₀ 

Question. Which of the following fluorides does not exist?
(a) NF₅
(b) PF₅
(c) AsF₅
(d) SbF₅ 

Question. Which one has the lowest boiling point?
(a) NH₃
(b) PH₃
(c) AsH₃
(d) SbH₃

Question. Number of electrons shared in the formation of nitrogen molecule is
(a) 6
(b) 10
(c) 2
(d) 8

Question. Nitrogen is relatively inactive element because
(a) its atom has a stable electronic configuration
(b) it has low atomic radius
(c) its electronegativity is fairly high
(d) dissociation energy of its molecule is fairly high.

Question. Pure nitrogen is prepared in the laboratory by heating a mixture of
(a) NH₄OH + NaCl
(b) NH₄NO₃ + NaCl
(c) NH₄Cl + NaOH
(d) NH₄Cl + NaNO₂. 

Question. Which of the following statement is not correct for nitrogen?
(a) Its electronegativity is very high.
(b) d-orbitals are available for bonding.
(c) It is a typical non-metal.
(d) Its molecular size is small.

Question. Urea reacts with water to form A which will decompose to form B. B when passed through Cu2+ (aq), deep blue colour solution C is formed. What is the formula of C from the following?
(a) CuSO₄
(b) [Cu(NH₃)₄]²⁺
(c) Cu(OH)₂
(d) CuCO₃·Cu(OH)₂

Question. Aqueous solution of ammonia consists of
(a) H⁺
(b) OH^–
(c) NH⁴⁺
(d) NH⁴⁺ and OH^–.

Question. Which of the following oxides of nitrogen is paramagnetic?
(a) NO₂
(b) N₂O₃
(c) N₂O
(d) N₂O₅ 

Question. Which of the following is a nitric acid anhydride?
(a) NO
(b) NO₂
(c) N₂O₅
(d) N₂O₃

Question. When copper is heated with conc. HNO3 it produces
(a) Cu(NO₃)₂, NO and NO₂
(b) Cu(NO₃)₂ and N₂O
(c) Cu(NO₃)₂ and NO₂
(d) Cu(NO₃)₂ and NO 

Question. Zn gives H₂ gas with H₂SO₄ and HCl but not with HNO₃ because
(a) Zn act as oxidising agent when react with HNO₃
(b) HNO3 is weaker acid than H₂SO₄ and HCl
(c) in electrochemical series Zn is above hydrogen
(d) NO₃– is reduced in preference to hydronium ion. 

Question. Sugarcane on reaction with nitric acid gives
(a) CO₂ and SO₂
(b) (COOH)₂
(c) 2HCOOH(two moles)
(d) no reaction. 

Question. Which of the following phosphorus is the most reactive?
(a) Scarlet phosphorus
(b) White phosphorus
(c) Red phosphorus
(d) Violet phosphorus

Question. Each of the following is true for white and red phosphorus except that they
(a) are both soluble in CS₂
(b) can be oxidised by heating in air
(c) consist of the same kind of atoms
(d) can be converted into one another.

Question. A compound ‘X’ upon reaction with H₂O produces a colourless gas ‘Y’ with rotten fish smell. Gas ‘Y’ is absorbed in a solution of CuSO₄ to give Cu₃P₂ as one of the products. Predict the compound ‘X’.
(a) Ca₃P₂
(b) NH₄Cl
(c) As₂O₃
(d) Ca₃(PO₄)₂

Question. PH₄I + NaOH forms
(a) PH₃
(b) NH₃
(c) P₄O₆
(d) P₄O₁₀