Chemistry

Chemical Bonding and Molecular Structure

Question:

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

Answer:

No, these cannot be taken as canonical forms because the positions of atoms have been changed.

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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.

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 3.

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 4.

Explain with the help of suitable example polar covalent bond.

Q 5.

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

Q 6.

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 7.

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

Q 8.

Write the type of hybridisation involved in  CH4,C2H4  and C2H2.

Q 9.

Account for the following:
(i) Water is a liquid while H2S is a gas
(ii) NH3 has higher boiling point than PH3.

Q 10.

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

Q 11.

Which of the following have identical bond order?
(a) CN (b) NO+                                           (c) 02                                               (d) 022-

Q 12.

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 13.

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 14.

Why  B2  is paramagnetic in nature while C2 is not?

Q 15.

Which is more polar CO2  or  N2O? Give reason.

Q 16.

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

Q 17.

(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?

Q 18.

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

Q 19.

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

Q 20.

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 21.

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

Q 22.

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

Q 23.

Arrange the following bonds ‘in order of increasing ionic character giving reason.
N-H, F-H, C-H and O-H

Q 24.

Define the bond-length.

Q 25.

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

Q 26.

Explain the non linear shape of H2S and non planar shape of PCl3 using valence shell electron pair repulsion theory.

Q 27.

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

Q 28.

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 29.

Use Lewis symbols to show electron transfer between the following atoms to form cations and anions (a) K and S (b) Ca and O (c) Al and N.

Q 30.

Draw diagrams showing the formation of a double bond and a triple bond between carbon atoms in  C2 H4 and  C2 H2  molecules.

Q 31.

Define antibonding molecular orbital.

Q 32.

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

Q 33.

What do you mean by Dipole moment? Draw the dipole diagram of H2O.

Q 34.

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

Q 35.

Predict the shapes of the following molecules on the basis of hybridization. BC13, ch4, co2, nh3

Q 36.

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

Q 37.

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

Q 38.

What is an ionic bond? With two suitable examples explain the difference between an ionic and covalent bond?

Q 39.

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

Q 40.

Explain the formation of a chemical bond.

Q 41.

Discuss the shape of the following molecules using the VSEPR model:
BeCl2, BCl3 , SiCl4, AsF5, H2S, PH3

Q 42.

Write the resonance structures for SO3,NO2 and NO3

Q 43.

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

Q 44.

Use molecular orbital theory to explain why the Be2 molecule does not exist.

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.

Write the state of hybridisation of boron in  BF3.

Q 48.

Explain why PC15 is trigonal bipyramidal whereas IF5 is square pyramidal.

Q 49.

Although geometries of NH3  and H20 molecules are distorted tetrahedral, bond angle in water is less than that of ammonia. Discuss.

Q 50.

Compare the relative stability of the following species and indicate their magnetic properties: O2, O2, O2 (Superoxide),O22- (peroxide)