Chemistry Class 11 NCERT Solutions: Chapter 4 Chemical Bonding and Molecular Structure Part 6

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Q:27. Draw diagrams showing the formation of a double bond and a triple bond between carbon atom in and molecules.

Answer:

The electronic configuration of in the excited state is:

In the formation of an ethane molecule , one hybrid orbital of carbon overlaps a hybridized orbital of another carbon atom, thereby forming a C-C sigma bond. The remaining two orbitals of each carbon atom form a sigma bond with two hydrogen atoms. The unhybridized orbital of one carbon atom undergoes sidewise overlap with the orbital of a similar kind present on another carbon atom to form a weak n-bond.

(A)

Description of C2H4

Sigma Bond Between Two Carbon Atoms

Description of C2H4

(B)

Orbital structure of C2H4 Choice 2

Orbital Structure of C2H4 Choice 2

Orbital structure of C2H4 Choice 2

(C)

Orbital structure of C2H4 Choice 3

Orbital Structure of C2H4 Choice 3

Orbital structure of C2H4 Choice 3

(D) figure:

Orbital structure of C2H4 Choice 4

Orbital Structure of C2H4 Choice 4

Orbital structure of C2H4 Choice 4

In the formation of molecule, each C-atom is sp hybridized with two 2p-orbitals in an unhybridized state. One sp orbital of each carbon atom overlaps with the other along the internuclear axis forming a c- c sigma bond. The second sp orbital of each C-atom overlaps a half- filled 1s-Orbital to form a bond.

The two unhybridized 2p-orbitals of the first carbon undergo sidewise overlap with the 2p orbital of another carbon atom, thereby two carbon atoms is made up of one sigma and two n-bonds.

(A)

Orbital structure of C2H2 Choice 1

Orbital Structure of C2H2 Choice 1

Orbital structure of C2H2 Choice 1

(B)

Orbital structure of C2H2 Choice 2

Orbital Structure of C2H2 Choice 2

Orbital structure of C2H2 Choice 2

(C)

Orbital structure of C2H2 Choice 3

Orbital Structure of C2H2 Choice 3

Orbital structure of C2H2 Choice 3

Q: 28. What is the total number of sigma and pi bonds in the following molecules?

(A)

(B)

Answer:

A single bond is a result of the axial overlap of bonding orbitals. Hence, it contributes a sigma bond. A multiple bond (double or triple bond) is always formed as a result of the sidewise overlap of orbitals. A pi-bond is always present in it. A triple bond is a combination of two pi-bonds and one sigma bond.

Structure of can be represented as:

Hence, there are three sigma and two pi-bonds in

The structure of can be represented as:

Figure:

Image showing sigma bonds and pi bond in structure of C2H4.

Image Showing Sigma Bonds and Pi Bond in Structure of C2H4.

Image showing sigma bonds and pi bond in structure of C2H4.

Hence, there are five sigma bonds and one pi-bond in

Q: 29. Considering x-axis as the internuclear axis which out of the following will not form a sigma bond and why?

(A)

(B)

(c)

(D)

Answer:

orbitals will not a form a sigma bond. Taking X-axis as the internuclear axis,

orbitals will undergo lateral overlapping, thereby forming a pi bond.

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