LEVEL-1
1. Arrange the following in order of increasing bond angles around central atom SF6,CF4,BF3
Ans: SF6,CF4,BF3
2. A single bond between two atoms is a sigma bond. Comment?
Ans: Bonding taking place along the nuclear axis.
3. Name an inorganic molecule showing sp3 and sp2 hybridization.
Ans: NH3 , BCl3
4. The two 0-0 bond distances in ozone molecule are equal justify.
Ans: Due to resonance
5. Define bond enthalpy and bond order?
Ans: Bond Enthalpy: the amount of energy required to break one mole bonds of a particular type between the atom in the gaseous state of a substance. Bond Order: According to Lewis concept, in a covalent bond, the bond order may be given as the number of bonds between two atoms in a molecule.
6. What is the shape of NH4+?
Ans: Tetrahedral
7. Which has larger dipole moment NH3 orNF3?
Ans: NH3
8. How many sigma and pi bond are present in C2H4 molecule?
Ans: 5 sigma and one pi bond
LEVEL-2
1. Explain the formation of chemical bond?
Ans: Due to the transfer or sharing of electrons.
2. Write octet rule and its significance and limitation.
Ans: The atoms of different elements take part in chemical combination in order to complete their octet or duplet in some cases such as H, Li, Be etc. This is known as octet rule. Limitations of Octet rule:
i) Odd number of electrons.
ii) Incomplete octet.
iii) Expanded octet
3. What is dipole moment? What is its significance?
Ans: Dipole moment is the product of Charge and distance between both the nucleus. It significance:
(i) Polarity between the charge
(ii) Ionic nature.
4. What is hybridization of atomic orbital?
Ans: The phenomenon of mixing of orbitals of the same atom with slight difference in energies so as to redistribute their energies and give new orbitals of equivalent energy and shape. The new orbitals which get formed are known as hybrid orbitals.
5. Discuss the shape of sp and sp2 hybrid orbital.
Ans: sp – linear and sp2 – trigonal planar
6. What are two different types of hydrogen bonding?
Ans: Inter and Intramolecular hydrogen bonding
LEVEL-3
1. Why the bond angle H-N-H is 107° and H-O-H is 105°, instead of 109°28’ characteristic of tetrahedral structure?
Ans: lone pair lone pair repulsion in H2O has more magnitude than that of lone pair bond pair repulsion in NH3.
2. What type of bonding would you expect between
a. A metal and a non metal?
b. A metal and another metal?
c. A non metal and a non metal?
Ans: a. Ionic bonding
b. metallic bonding
c. covalent bonding
3. Which one of the sigma or pie bond is stronger and why?
Ans: Sigma bond is more stronger than pi bond because of more extent of overlapping.
4. Differentiate between a polar and a non polar covalent bond?
Ans: Polar covalent bond is formed between two non-metals of different electro negativities. Non-polar covalent bond is formed between two non-metals of same or nearly same electro negativities.
5. Explain the VSEPR theory.
Ans:
i. The shape of the molecule depends upon the number of electron pairs (bonded or non-bonded) around the central atom.
ii. The electron pairs around the central atom tend to repel one another since the electron clouds are negatively charged.
iii. The electron pairs in space tend to occupy such positions that they are at maximum distance apart and the repulsive interactions are minimum.
iv. A multiple bond is treated as if it is a single bond and the electron pairs which constitute the bond may be regarded as single pairs.
v. Where two or more resonance structures can represent a molecule, the VSEPRmodel is applicable to any such structure.
vi. Gillespie and Nyholmn stated that the electron pairs existing as lone pairs cause greater repulsive interactions as compared to bonded electron pairs. In the light of this, the repulsive interactions follow the order:
Lone pair – Lone pair > Lone pair – Bond pair > Bond pair – Bond pair
