Chemistry

Chemical Bonding and Molecular Structure

Question:

Write the Lewis dot symbols of the following elements and predict their valencies.  (i) Cl (ii) P

Answer:

ncert-solutions-for-class-11-chemistry-chapter-4-chemical-bonding-and-molecular-structure-23

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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.

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

Q 4.

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 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.

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

Q 8.

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

Q 9.

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

Q 10.

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 11.

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

Q 12.

Write the state of hybridisation of boron in  BF3.

Q 13.

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

Q 14.

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

Q 15.

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

Q 16.

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

Q 17.

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

Q 18.

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

Q 19.

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 20.

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 21.

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

Q 22.

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

Q 23.

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

Q 24.

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

Q 25.

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 26.

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 27.

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 28.

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

Q 29.

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

Q 30.

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

Q 31.

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

Q 32.

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

Q 33.

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

Q 34.

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

Q 35.

(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 36.

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 37.

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

Q 38.

Which of the following statements are correct about CO32- ?
(a) The hybridization of central atom is sp3.
(b) Its resonance structure has one C – O single bond and two C = O double bonds.
(c) The average formal charge on each oxygen atom is 0.67 units.
(d) All C – O bond lengths are equal.

Q 39.

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

Q 40.

Explain the formation of a chemical bond.

Q 41.

Write the significance/applications of dipole moment.

Q 42.

What is meant by hybridisation of atomic orbitals? Describe the shapes of sp, sp2, sp3 hybrid orbitals.

Q 43.

Is there any change in the hybridisation ofB and N atoms as a result of the following reaction ?  BF3 + NH3 ——-> F3 B.NH3

Q 44.

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

Q 45.

Write the significance of plus and minus sign in representing the orbitals,

Q 46.

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

Q 47.

What is meant by bond pairs of electrons?

Q 48.

Arrange the following, according to increasing covalent nature.
NaCl, MgCl2, AlCl3

Q 49.

Define covalent bond according to orbital concept?

Q 50.

Why  B2  is paramagnetic in nature while C2 is not?