Chemistry

Chemical Bonding and Molecular Structure

Question:

Which out of NH3 and NF3 has higher dipole moment and why?

Answer:

In NH3 and NF3, the difference in electronegativity is nearly same but the dipole moment of NH3 = (1.46D)  For Example, NH3 = (0.24D)
In NH3, the dipole moments of the three N—H bonds are in the same direction as the lone pair of electron. But in NF3, the dipole moments of the three N—F bonds are in the direction opposite to that of the lone pair. Therefore, the resultant dipole moment in NH3 is more than in NF3.

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Chemical Bonding and Molecular Structure

Q 1.

Why  N2  is more stable than  O2? Explain on the basis of molecular orbital theory.

Q 2.

Explain with the help of suitable example polar covalent bond.

Q 3.

Match the shape of molecules in Column I with the type of hybridization in Column II.

Column I Column II
(i) Tetrahedral (a) sp2
(ii) Trigonal (b) sp
(iii) Linear (c) sp3

Q 4.

Give the shapes of the following molecules:
(i) AB3  (ii) AB4

Q 5.

Which out of NH3 and NF3 has higher dipole moment and why?

Q 6.

Match the species in Column I with the geometry/shape in Column II.

Column I Column II
(i) H30+ (a) Linear
(ii) HC = CH (b) Angular
(iii) Cl02 (c) Tetrahedral
(iv) NH+4 (d) Trigonal bipyramidal
(e) Pyramidal

Q 7.

Describe the change in hybridisation (if any) of the Al atom in the following reaction.  AlCl3 + Cl ——>AlCl4- .

Q 8.

Which hybrid orbitals are used by carbon atoms in the following molecules?
(a) CH3-CH3 (b) CH3-CH = CH2 (c) CH3-CH2-OH (d) CH3-CHO (e) CH3COOH.

Q 9.

Predict the shapes of the following molecules using VSEPR theory?
(i) BeCl2(ii) SiCl4

Q 10.

Write the state of hybridisation of boron in  BF3.

Q 11.

Arrange  O2,O2,O22-, O2+in increasing order of bond energy.

Q 12.

Group the following in linear and non-linear molecules: H20, HOC1, BeCl2 C120

Q 13.

How do you express the bond strength in terms of bond order?

Q 14.

Define electronegativity. How does it differ from electron gain enthalpy?

Q 15.

Define hydrogen bonds. Is it weaker or stronger than the van der Waals forces?

Q 16.

Out of bonding and antibonding molecular orbitals, which one has lower energy and which one has higher stability?

Q 17.

Explain why BeH2   molecule has a zero dipole moment although the Be-H bonds are polar.

Q 18.

In N03 ion, the number of bond pairs and lone pairs of electrons on nitrogen atom are
(a) 2, 2                                       (b) 3, 1                                           (c) 1,3                                           (d) 4, 0

Q 19.

Which of the following attain the linear structure?
(a) BeCl2
(b) NCO+                                    
(c) N02                                          
(d) CS2

Q 20.

Draw the resonating structure of (i) Ozone molecule (ii) Nitrate ion

Q 21.

Write Lewis symbols for the following atoms and ions: S and  S2– ; Al and  Al3+; H and H

Q 22.

3PO3  can be represented by structures 1 and 2 shown below. Can these two structures be taken as the canonical forms of the resonance hybrid representing  H3PO3? If not, give reasons for the same.
ncert-solutions-for-class-11-chemistry-chapter-4-chemical-bonding-and-molecular-structure-7

Q 23.

The skeletal structure of  CH3COOH  as shown below is correct, but some of the bonds are shown incorrectly. Write the correct Lewis structure for acetic acid.
ncert-solutions-for-class-11-chemistry-chapter-4-chemical-bonding-and-molecular-structure-12

Q 24.

Write the important conditions required for the linear combination of atomic orbitals to form molecular orbitals.

Q 25.

Name the two conditions which must be satisfied for hydrogen bonding to take place in a molecule.

Q 26.

What are Lewis structures? Write the Lewis structure of  H2, BeF2  and  H2O.

Q 27.

Define Lattice energy. How is Lattice energy influenced by (i) Charge on the ions (ii) Size of the ions?

Q 28.

What are the main postulates of Valence Shell Electron Pair Repulsion (VSEPR) theory?

Q 29.

Explain the diamagnetic behaviour of  P2  molecule on the basis of molecular orbital theory.

Q 30.

(a) Define dipole moment. What are the units of dipole moment?
(b) Dipole moment values help in predicting the shapes of covalent molecules. Explain.

Q 31.

Polarity in a molecule and hence the dipole moment depends primarily on electronegativity of the constituent atoms and shape of a molecule. Which of the following has the highest dipole moment?
(a) C02
(b) HI                                            
(c) H20                                          
(d) S02

Q 32.

In PO43- ion the formal charge on the oxygen atom of P – O bond is
(a) +1                                           (b) -1                                               (c) -0.75                                       (d) +0.75

Q 33.

Which molecule/ion out of the following does not contain unpaired electrons?
(a) N+2
(b) 02                                                
(c) O22-                                        
(d) B2

Q 34.

In which of the following substances will hydrogen bond be strongest?
(a) HCl
(b) H20                                          
(c) HI                                            
(d) H2S

Q 35.

Using molecular orbital theory, compare the bond energy and magnetic character of 0+2 and O2

Q 36.

Explain the formation of a chemical bond.

Q 37.

Explain the important aspects of resonance with reference to the  C032-ion.

Q 38.

Write the significance/applications of dipole moment.

Q 39.

Considering X-axis as the intemuclear axis which out of the following will not form a sigma bond and why? (a) Is and Is (b) Is and  2px  (c)  2py  and 2py (d) Is and 2s

Q 40.

What do you understand by bond pairs and lone pairs of electrons? Illustrate by giving one example of each type.

Q 41.

How is bond order related to the stability of a molecule?

Q 42.

What is meant by bond pairs of electrons?

Q 43.

Which of the following has larger bond angle in each pair?
(i) CO2, BF3 (ii) NH3, CH4

Q 44.

Define covalent bond according to orbital concept?

Q 45.

Why  B2  is paramagnetic in nature while C2 is not?

Q 46.

Why ethyl alcohol is completely miscible with water?

Q 47.

State the types of hybrid orbitals associated with (i) P in PCl5  and (ii) S in  SF6

Q 48.

Define antibonding molecular orbital.

Q 49.

Define bond order. How is it related to the stability of a molecule?

Q 50.

(a) How many a and n bonds are present in
ncert-solutions-for-class-11-chemistry-chapter-4-chemical-bonding-and-molecular-structure-34
(b) Why Hf is more stable than H2?
(c) Why is B2 molecule paramagnetic?