Question 1

What is the proportionality between (I) Bond length and size of atom (II) Bond length and multiplicity of bond respectively?

Accepted Answer

Bond length is the equilibrium distance between the nuclei of two bonded atoms in a molecule. As the size of the bonded atoms increases, the distance between their nuclei increases. Thus, bond length is directly proportional to the size of the atom. Bond multiplicity refers to the number of bonds between two atoms (single, double, triple). As bond multiplicity increases, the bond becomes stronger and the atoms are pulled closer together, decreasing the bond length. Thus, bond length is inversely

Question 2

Identify linear molecule from following.

Accepted Answer

For SO _2, the central sulphur atom has 2 bond pairs and 1 lone pair. The hybridization is sp^2 and the shape is bent. For BCl _3, the central boron atom has 3 bond pairs and 0 lone pairs. The hybridization is sp^2 and the shape is trigonal planar. For CO _2, the central carbon atom has 2 bond pairs (sigma bonds) and 0 lone pairs. The hybridization is sp and the shape is linear. For NH _3, the central nitrogen atom has 3 bond pairs and 1 lone pair. The hybridization is sp^3 and the shape is trig

Question 3

Which from following gases is least soluble in water under same conditions of temperature and pressure ?

Accepted Answer

Water is a polar solvent. Gases that are polar, can form hydrogen bonds, or react with water are highly soluble in it. HCl and NH _3 are highly soluble due to ionization and hydrogen bonding, respectively. CO _2 is moderately soluble as it reacts with water to form carbonic acid. O _2 is a non-polar gas and interacts with water only through weak dipole-induced dipole forces, making it the least soluble among the given gases. Answer: O _2

Question 4

Which is the correct decreasing order of boiling points for different compounds from following ?

Accepted Answer

The boiling point of haloalkanes increases with an increase in the molecular mass and the size of the halogen atom due to the stronger van der Waals forces of attraction. Comparing the given compounds: CH _3 Cl has one chlorine atom. CH _3 Br has one bromine atom, which is heavier and larger than chlorine. CH _2 Br _2 has two bromine atoms. CHBr _3 has three bromine atoms. The molecular mass follows the order: CHBr _3 > CH _2 Br _2 > CH _3 Br > CH _3 Cl . Therefore, the decreasing order of boili

Question 5

Which of the following is favourable condition for the formation of ionic bond ?

Accepted Answer

The formation of an ionic bond involves the transfer of electrons from a metal atom to a non-metal atom. The metal atom loses an electron to form a cation. This process requires energy, which is the ionization enthalpy. A lower ionization enthalpy means the metal can easily lose its valence electrons, favoring cation formation. The non-metal atom gains an electron to form an anion. This process releases energy, which is measured as the electron gain enthalpy. A high negative value of electron ga

Question 6

What is the number of bond pair of electrons and lone pair of electrons present in the valence shell of chalcogens in their hydride ?

Accepted Answer

Chalcogens belong to Group 16 of the periodic table and have 6 valence electrons (ns^2 np^4). The general formula for the hydrides of chalcogens is H_2E (where E = O, S, Se, Te, Po). In the formation of H_2E, the chalcogen atom shares two of its valence electrons with two hydrogen atoms to form two single covalent bonds. This results in 2 bond pairs of electrons. The remaining 4 valence electrons on the chalcogen atom do not participate in bonding and exist as 2 lone pairs of electrons. Thus, th

Question 7

What is the number of sp^3 hybrid carbon atoms in HO ( CH _2)_2 CH ( CH _3)_2?

Accepted Answer

The given molecule is 3-methylbutan-1-ol, with the expanded structural formula HO - CH _2- CH _2- CH ( CH _3)- CH _3. In this structure, every carbon atom is bonded to four other atoms (either carbon, hydrogen, or oxygen) entirely through single ( ) bonds. Since there are no bonds present, all the carbon atoms are sp^3 hybridized. Counting the carbon atoms: Two - CH _2- groups 2 carbon atoms One - CH - group 1 carbon atom Two - CH _3 groups 2 carbon atoms Total number of sp^3 hybridized carbon a

Question 8

Identify correct order for repulsion between electron pair present in valence shell of central atom of molecule?

Accepted Answer

According to VSEPR theory, the electron pairs in the valence shell of the central atom repel each other to minimize electron-electron repulsion. Lone pairs (Lp) are localized on the central atom and are attracted by only one nucleus, so they occupy more space and exert greater repulsion. Bond pairs (Bp) are shared between two atoms and are attracted by two nuclei, so they occupy less space and exert lesser repulsion. Thus, the correct order of repulsion between electron pairs is Lp-Lp > Lp-Bp >

Question 9

Which among the following molecule exhibits paramagnetism?

Accepted Answer

According to Molecular Orbital Theory, the electronic configuration of O _2 (16 electrons) is: _ 1s ^2 ^ * _ 1s ^2 _ 2s ^2 ^ * _ 2s ^2 _ 2p_z ^2 _ 2p_x ^2 _ 2p_y ^2 ^ * _ 2p_x ^1 ^ * _ 2p_y ^1 Due to the presence of two unpaired electrons in the degenerate antibonding ^ * molecular orbitals, O _2 is paramagnetic. N _2 (14 electrons) and F _2 (18 electrons) have all their electrons paired in their molecular orbitals, making them diamagnetic. O _3 (ozone) also has all its electrons paired and is d

Question 10

Which of the following ethers is gaseous at room temperature ?

Accepted Answer

Dimethyl ether and ethyl methyl ether (methoxyethane) are gases at room temperature. Other lower homologues of ethers, such as diethyl ether (ethoxyethane), 1-methoxypropane, and 1-ethoxypropane, are colourless, highly volatile liquids at room temperature. Therefore, methoxyethane is gaseous at room temperature. Answer: Methoxyethane

Question 11

Which from following gases is least soluble in water at same temperature and pressure ?

Accepted Answer

Solubility of a gas in water depends on its ability to interact with water molecules. Water is a polar solvent. NH _3 is highly soluble in water due to its ability to form intermolecular hydrogen bonds with water. HCl is a polar molecule that ionizes completely in water, making it highly soluble. CO _2 is moderately soluble because it reacts with water to form carbonic acid ( H _2 CO _3). N _2 is a non-polar diatomic gas that neither reacts with water nor forms hydrogen bonds. Therefore, it has

Question 12

Select the incorrect statement from the following.

Accepted Answer

Both NH _3 and NF _3 have a central nitrogen atom with sp^3 hybridization and one lone pair, giving them a trigonal pyramidal shape. Both are polar molecules. In NH _3, nitrogen is more electronegative than hydrogen. The bond dipole moments of the three N-H bonds are directed towards the nitrogen atom. Their resultant dipole moment is in the same direction as the orbital dipole due to the lone pair, leading to a higher net dipole moment. In NF _3, fluorine is more electronegative than nitrogen.

Question 13

Which of the following metal halides have more covalent character?

Accepted Answer

According to Fajan's rules, the covalent character of a metal halide increases with an increase in the positive charge on the central metal cation. A higher charge on the cation results in greater polarizing power, which increases the covalent character of the bond. The oxidation states of the central metal cations in the given options are: SnCl _2: +2 PbCl _4: +4 SbCl _3: +3 PbCl _2: +2 Since Pb in PbCl _4 has the highest oxidation state of +4, the Pb ^ 4+ ion has the maximum polarizing power.

Question 14

Which of the following compound has square pyramidal structure?

Accepted Answer

The shape of the molecules can be determined using VSEPR theory by calculating the number of bond pairs (bp) and lone pairs (lp) on the central Xenon (Xe) atom, which has 8 valence electrons. For XeF _4: Xe forms 4 single bonds with F atoms, using 4 electrons. Remaining electrons = 4 (2 lone pairs). With 4 bp and 2 lp, the hybridization is sp^3d^2 and the shape is square planar. For XeF _6: Xe forms 6 single bonds with F atoms, using 6 electrons. Remaining electrons = 2 (1 lone pair). With 6 bp

Question 15

What is formal charge on sulphur in sulphuric acid molecule?

Accepted Answer

The most stable Lewis structure of sulphuric acid (H_2SO_4) minimizes the formal charge by expanding the octet of the central sulphur atom. In this structure, sulphur forms two double bonds with two oxygen atoms and two single bonds with two hydroxyl (-OH) groups. The formula for formal charge is: Formal charge = (Valence electrons) - (Non-bonding electrons) - 1 2 (Bonding electrons) For the sulphur atom in H_2SO_4: Number of valence electrons = 6 Number of non-bonding electrons = 0 Number of bo

Question 16

Identify the number of lone pair and bond pair electrons present in the valence shell of central atom in BrF _3.

Accepted Answer

The central atom in BrF _3 is Bromine ( Br ). Number of valence electrons in Br = 7. Bromine forms 3 single bonds with 3 Fluorine atoms. Therefore, the number of bond pairs is 3. Number of electrons used in bonding = 3. Remaining valence electrons on the central atom = 7 - 3 = 4. Number of lone pairs = 4 2 = 2. Thus, the central atom has 2 lone pairs and 3 bond pairs of electrons. Answer: 2 _ Lone pair and 3 _ Bond pair of electrons

Question 17

Which of the following statements regarding Pi ( ) bond is NOT true ?

Accepted Answer

A pi ( ) bond is formed by the lateral or sideways overlapping of half-filled atomic orbitals (like p or d orbitals) after the formation of a sigma ( ) bond. Because the extent of overlapping in a bond is less than that in a bond, a bond is weaker than a bond. The presence of a bond between two atoms increases the bond order (e.g., from single to double or triple bond). An increase in bond order leads to a stronger attractive force between the atoms, which decreases the bond length. For example,

Question 18

Identify a molecule having highest dipole moment from following.

Accepted Answer

The dipole moment of a molecule depends on its geometry and the electronegativity difference between its constituent atoms. For H _2 O , the oxygen atom is highly electronegative and possesses two lone pairs. The molecule has a bent structure, and the bond dipoles along with the lone pair dipoles reinforce each other, resulting in a high dipole moment of approximately 1.85 D . For NH _3, the nitrogen atom has one lone pair and the molecule is trigonal pyramidal. Its dipole moment is approximatel

Question 19

What is the total number of electrons present in bonding and antibonding orbitals respectively in F _2 molecule according to MO theory ?

Accepted Answer

The atomic number of fluorine ( F ) is 9. Therefore, the total number of electrons in the F _2 molecule is 18. According to Molecular Orbital Theory, the electronic configuration of F _2 is: _ 1s ^2 ^ * _ 1s ^2 _ 2s ^2 ^ * _ 2s ^2 _ 2p_z ^2 _ 2p_x ^2 _ 2p_y ^2 ^ * _ 2p_x ^2 ^ * _ 2p_y ^2 The electrons present in orbitals without an asterisk are bonding electrons (N_b), and those in orbitals with an asterisk are antibonding electrons (N_a). Number of bonding electrons (N_b) = 2 ( _ 1s ) + 2 ( _ 2

Question 20

Which of the following molecules is paramagnetic?

Accepted Answer

According to molecular orbital theory, the electronic configurations of the given molecules are written to determine the presence of unpaired electrons. Li _2 (6 electrons): _ 1s ^ 2 _ 1s ^ *2 _ 2s ^ 2 Since all electrons are paired, it is diamagnetic. N _2 (14 electrons): _ 1s ^ 2 _ 1s ^ *2 _ 2s ^ 2 _ 2s ^ *2 _ 2p_x ^ 2 _ 2p_y ^ 2 _ 2p_z ^ 2 Since all electrons are paired, it is diamagnetic. O _2 (16 electrons): _ 1s ^ 2 _ 1s ^ *2 _ 2s ^ 2 _ 2s ^ *2 _ 2p_z ^ 2 _ 2p_x ^ 2 _ 2p_y ^ 2 _ 2p_x ^ *1

Chemical Bonding and Molecular Structure — Previous Year Questions & Solutions