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Chemical Bonding and Molecular Structure

Multiple Choice Questions

121.

The number of sigma (σ) and pi ( $π$ ) bonds present in 1, 3, 5, 7-octatetraene respectively are

14 and 3
17 and 4
16 and 5
15 and 4

122.

The molecule that contains only sp² hybrid carbon atoms is

isoprene
acrylonitrile
but-1-ene
1,3-butadiene

123.

Among the following, the molecule of highest dipole moment is

CCl₄
NH₃
H₂O
CHCl₃

124.

The incorrectly matched pair, among the following is-

BrF₅ - Trigonal bipyramidal
SF₄ - See-saw
ClF₃ - T-shape
NH₃ - Trigonal pyramidal

125.

Which one of the following has the shortest bond length?

C - H
C - N
C - F
C - C

126.

Pick out the wrong statement.

Nitrogen has the ability to form p $π$ -p $π$ bonds with itself
Bismuth forms metallic bonds in elemental state
Catenation tendency is higher in nitrogen when compared with other elements of the same group
Nitrogen has higher first ionization enthalpy when compared with other elements of the same group

127.

The wrong statement about the interstitial compounds is

their melting points are lower than those of pure metals
they retain metallic conductivity
they are chemically inert
their bonds are neither ionic non covalent

128.
Which of the following is not correct with respect to bond length of the species?

C₂ > $C_{2}^{2 -}$

$B_{2}^{+}$ > B₂

${Li}_{2}^{+}$ > Li₂

O₂ > O $_{2}^{-}$

O₂ > O $_{2}^{-}$

Greater the bond order, shorter is the bond length.

$∴ Bond order \propto \frac{1}{bond length}$

(i) Electronic configuration and bond order of C₂ and C $_{2}^{2 -}$ ions-

C₂ : KK σ2s², σ*2s², $π 2 p_{x}^{2}, π 2 p_{y}^{2}$

Bond order = $\frac{1}{2}$ (6 - 2) = 2

C $_{2}^{2 -}$ : KK σ2s², σ*2s², $π 2 p_{x}^{2}, π 2 p_{y}^{2}, σ 2 p_{z}^{2}$

Bond order = $\frac{1}{2}$ (8 - 2) = 3

$∴$ The order of bond length : C₂ > C $_{2}^{2 -}$

(ii) Electronic configuration and bond orders of B $_{2}^{+}$ and B₂-

B₂ : KK σ2s², σ*2s², $π 2 p_{x}^{1}, π 2 p_{y}^{1}$

Bond order = $\frac{1}{2}$ (4 - 2) = 1

B $_{2}^{+}$ : KK σ2s², σ*2s², $π 2 p_{x}^{1}$

Bond order = $\frac{1}{2}$ (3 - 2) = $\frac{1}{2}$

$∴$ The order of bond length : B $_{2}^{+}$ > B₂

(iii) Electronic configuration and bond order of Li₂ and Li $_{2}^{+}$

Li₂ : KK σ2s²

Bond order = $\frac{1}{2}$ ( 2 - 0) = 1

Li $_{2}^{+}$ : KK σ2s¹

Bond order = $\frac{1}{2}$ ( 1 - 0) = $\frac{1}{2}$

$∴$ The order of bond length : Li $_{2}^{+}$ > Li₂

(iv) Electronic configuration and bond order of O₂ and O $_{2}^{-}$

O₂ : KK σ2s², σ*2s², $σ 2 p_{z}^{2}, π 2 p_{x}^{2}, π 2 p_{y}^{2}, π * 2 p_{x}^{1}, π * 2 p_{y}^{1}$

Bond Order = $\frac{1}{2}$ ( 8 - 4) = 2

O $_{2}^{-}$ : KK σ2s², σ*2s², σ2p $_{z}^{2}$ , $π 2 p_{x}^{2}, π 2 p_{y}^{2}, π * 2 p_{x}^{2}, π * 2 p_{y}^{1}$

Bond order = $\frac{1}{2}$ ( 8 - 5) = 1.5

$∴$ The correct order of bond length = O $_{2}^{-}$ > O₂

129.

Substance which is weakly repelled by a magnetic field is

O₂
H₂O
CrO₂
Fe₃O₄

130.

The bonds present in the structure of dichromate ion are

four equivalent Cr-O bonds only
six equivalent Cr-O bonds and one Cr - O - O bond
six equivalent Cr-O bonds and one O-O bond
eight equivalent Cr-O bonds

Previous Year Papers

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Multiple Choice Questions

128. Which of the following is not correct with respect to bond length of the species? C2 > C22- B2+ > B2 Li2+ > Li2 O2 > O2-

128.
Which of the following is not correct with respect to bond length of the species?

C₂ > $C_{2}^{2 -}$

$B_{2}^{+}$ > B₂

${Li}_{2}^{+}$ > Li₂

O₂ > O $_{2}^{-}$