Q.1. Among the 15th group elements, as we move from nitrogen to bismuth, the pentavalency becomes less pronounced and trivalency becomes more pronounced due to
(a) Non metallic character
(b) Inert pair effect
(c) High electronegativity
(d) Large ionization energy

Answer Ans. (b)

Q.2. Which of the following statements 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

Answer Ans. (b) In case of nitrogen, d-orbitals are not available.

Q.3. Collectively the elements of group 15 are called –
(a) pnicogens
(b) pnicopens
(c) nicopen
(d) None of these

Answer Ans. (a) Collectively these elements are called pnicogens and their compound pniconides.

Q.4. Ionic radii (in Å) of As³⁺, Sb³⁺ and Bi³⁺ follow the order
(a) As³⁺ > Sb³⁺ > Bi³⁺
(b) Sb³⁺ > Bi³⁺ >As³⁺
(c) Bi³⁺ > As³⁺ > Sb³⁺
(d) Bi³⁺ > Sb³⁺ > As³⁺

Answer

Q.5. Which one of the following elements is most metallic ?
(a) P
(b) As
(c) Sb
(d) Bi

Answer Ans. (d) Metallic character increases down the group, Bi is most metallic

Q.6. Which of the follow group 15 element forms metallic bonds in elemental state ?
(a) As
(b) P
(c) Sb
(d) Bi

Answer Ans. (d) Bismuth forms metallic bonds in elemental state.

Q.7. The three important oxidation states of phosphorus are
(a) –3, +3 and +5
(b) –3, +3 and –5
(c) –3, +3 and +2
(d) –3, +3 and +4

Answer Ans. (a) –3, +3, +5

Q.8. Which of the following statement is incorrect for group 15 elements ?
(a) Order of ionization enthalpies is Δ_iH₁ < Δ_iH₂ < Δ_iH₃
(b) The boiling point and melting point increases from top to bottom in the group
(c) Dinitrogen is a gas while all others are solids
(d) All statements are correct

Answer Ans. (b) The melting point in group 15 increases upto arsenic and then decreases upto bismuth.

Q.9. 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

Answer Ans. (d) N₂ molecule contains triple bond between N atoms having very high dissociation energy (946 kJ mol–1) due to which it is relatively inactive.

Q.10. Which of the following has the highest pπ – pπ bonding tendency ?
(a) N
(b) P
(c) As
(d) Sb

Answer Ans. (a) Nitrogen due to small size is able to show pπ-pπ lateral overlap forming N≡N, rest elements due to bigger size are not able to show pπ-pπ lateral overlap.

Q.11. Pick out the wrong statement.
(a) Nitrogen has the ability to form pπ-pπ bonds with itself.
(b) Bismuth forms metallic bonds in elemental state.
(c) Catenation tendency is higher in nitrogen when compared with other elements of the same group.
(d) Nitrogen has higher first ionisation enthalpy when compared with other elements of the same group.

Answer Ans. (c) Catenation tendency is higher in phosphorus when compared with other elements of same group.

Q.12. Nitrogen forms N₂, but phosphorus is converted into P₄ from P, the reason is
(a) Triple bond is present between phosphorus atom
(b) p_π – p_π bonding is strong
(c) p_π – p_π bonding is weak
(d) Multiple bond is formed easily

Answer Ans. (c)

Q.13. What causes nitrogen to be chemically inert ?
(a) Multiple bond formation in the molecule
(b) Absence of bond polarity
(c) Short internuclear distance
(d) High bond energy

Answer Ans. (d)

Q.14. Pentavalence in phosphorus is more stable when compared to that of nitrogen even though they belong to same group. This is due to
(a) dissimilar electronic configuration
(b) due to presence of vacant d-orbitals
(c) reactivity of phosphorus
(d) inert nature of nitrogen

Answer Ans. (b) Phosphorous can achieve coordination number 5 due to vacant d atomic orbitals in valence shell which is not possible in nitrogen

Q.15. Which one has the lowest boiling point ?
(a) NH₃
(b) PH₃
(c) AsH₃
(d) SbH₃

Answer Ans. (b)