4

Q1. The electrovalent linkage is present in

• O₂ molecule
• CHCl₃ molecule
• NaBr molecule
• CCl₄ molecule

Solution

The electrovalent linkage is present in NaBr molecule.

Q2. Which of the following has a square pyramidal shape?

• NH₃
• XeF₄
• BrF₅
• ClF₃

Solution

The shape of BrF₅ is square pyramidal.

Q3. Which of the following statements relating bond order and bond enthalpy are correct?

• With increase in bond order bond enthalpy increases
• With decrease in bond length bond order decreases
• With increase in bond order bond enthalpy decreases
• With increase in bond length bond order increases

Solution

With increase in bond order bond enthalpy increases.

Q4. Which of the following statement is not true for resonance?

• Resonance averages the bond characteristics as a whole.
• Resonance stabilizes the molecule.
• Canonical forms have real existence.
• Resonance is represented by a double arrow.

Solution

Canonical forms have no real existence.

Q5. The decreasing order of the repulsive interactions between various electron pairs is:

• lp-lp>lp-bp>bp-bp
• bp-bp>lp-lp>lp-bp
• lp-bp>lp-lp>bp-bp
• lp-bp>bp-bp=lp-lp

Solution

The bond pair of electrons is shared by two atoms whereas the lone pair of electrons is only under the influence of central atom. So the electron cloud of lone pair occupies more space as compared to the bond pair. This causes greater repulsion between the lone pairs as compared to lone pair-bond pair and bond pair-bond pair interactions.

Q6. Who discovered the octet rule?

• Kossel and Lewis
• Langmuir
• Debye
• Boyle

Solution

Kossel and Lewis

Q7. In sp³ hybridization how many atomic orbitals are involved?

• 1
• 2
• 3
• 4

Solution

In sp³ hybridization one s and three p orbitals are involved in hybridization.

Q8. Valence bond theory was introduced by:

• Pauling
• Lewis
• Heitler
• Gillespie

Solution

Heitler and London introduced the Valence bond theory.

Q9. The bond order of Li₂ molecule is:

• 1
• 2
• 3
• 0

Solution

The molecular orbital configuration of Li₂ is : So, its bond order =

Q10. Which type of hybridization leads to three dimensional geometry of bonds around the carbon atom?

• sp
• sp²
• sp³
• sp⁴

Solution

sp³ hybridization leads to three dimensional geometry of bonds around the carbon atom.

Q11. Which of these compounds is most likely to be ionic?

• GaAs
• SrBr₂
• CBr₄
• H₂O

Solution

Ionic compounds will be formed more easily between the elements with comparatively low ionization enthalpy and elements with comparatively high negative value of electron gain enthalpy.

Q12. When an element of very low ionisation potential reacts with an element of very high electron affinity:

• A weak ionic bond is formed
• A strong ionic bond is formed
• A polar covalent bond is formed
• A coordinate bond is formed

Solution

When an element of very low ionisation potential reacts with an element of very high electron affinity a strong ionic bond is formed because the transfer of electrons is very easy from an element of very low ionisation potential to an element of high electron affinity.

Q13. The minimum internuclear distance is present in:

• O₂
• O₂⁺
• O₂^-
• O₂^2-

Solution

Among the given options O₂⁺ has the highest bond order. So it forms the strongest bond, the bond order of O₂^2- is 1, O₂^- is 1.5, O₂ is 2 and O₂⁺ is 2.5 and hence it has the shortest bond length.

Q14. An orbital is the region of space around the _______ where the probability of finding an electron is maximum.

• Electron
• Proton
• Neutron
• Nucleus

Solution

An orbital is the region of space around the nucleus where the probability of finding an electron is maximum.

Q15. Which one of them is an odd-electron molecule?

• NO
• CO₂
• SF₆
• BCl₃

Solution

Octet rule is not satisfied for NO.

Q16. Valence bond theory explains:

• Directional properties of bonds in molecules
• Formal charge on the atoms in molecules
• Resonance
• Polarity of bonds

Solution

VBT explains the formation and directional properties of bonds in polyatomic molecules.

Q17. Element X is strongly electropositive and Y is strongly electronegative. Both are univalent. The compound formed would be

• X⁺Y⁻
• X – Y
• X⁻ Y⁺
• X = Y

Solution

Electropositive elements form positive ions and electronegative elements form anions. Both are held together by electrostatic forces of attraction.

Q18. Among the following molecules octet rule is not obeyed by:

• PCl₃
• CO₂
• OF₂
• ClF₃

Solution

The central atom of ClF₃ has more than eight electrons in its valence shell and forms super octet molecule.

Q19. In which of these pairs of atoms would the bond be the least polar (i.e., lowest percent ionic character)?

• H₂O
• H₂S
• BF₃
• HCl

Solution

The bond dipole of three B - F bonds give a net sum of zero because resultant of any two dipoles's equal & opposite to dipole of third bond.

Q20. Ionic bond is present in which of the following species:

• O₂
• CHCl₃
• NaBr
• CCl₄

Solution

Ionic bond is formed between an electropositive and electronegative element.

Q21. Hybridisation involves:

• Resonance and the calculation of formal charges
• The mixing of atomic orbitals
• Ionically bonded compounds
• Individual atomic orbitals on a lone atom

Solution

Hybridisation is a process of intermixing of atomic orbitals of slightly different energies to redistribute their energies, resulting in the formation of a new set of orbitals of equivalent energies and shapes.

Q22. The compound with the lowest boiling point among the following is:

• HBr
• HI
• HF
• HCl

Solution

Boiling point of covalent compounds(HF,HCl,HBr,HI) increases with increase in their molecular weight due to increase in van der Waal’s forces of attraction among molecules.   HF shows H-bonding possess higher boiling point or less volatile nature. HCl< HBr<HI<HF  

Q23. Though H₂O and CO₂ are triatomic molecules, why is CO₂ a non - polar molecule?

• Because C forms double bonds
• Because CO₂ is gas
• Due to linear structure, bond dipoles of two C = O bonds cancel each other
• Due to linear structure

Solution

In case of polyatomic molecule , C = O bond has dipole of 2.3 D. Due to linear structure, bond dipoles of two C = O bonds cancel each other.

Q24. Which molecule has a bent shape?

• CO₂
• BeH₂
• NF₃
• H₂O

Solution

Water has 2 lone pairs and thus the bond angle is reduced to 104.5 from 109.5

Q25. Among the following bonds, the most ionic bond is formed between:

• Cs and Cl
• Al and Cl
• C and Cl
• H and Cl

Solution

The bond formed between Cs-Cl is most ionic because the difference between electronegativities of Cs and Cl is highest among given choices.

Q26. The percentage of s character in sp³ hybridized orbital is:

• 25%
• 30%
• 50%
• 35%

Solution

The sp³ hybridized orbital has 25% s- character and 75% p- character.

Q27. The number of lone pairs of electrons on SF₄, CF₄ and XeF₄ are:

• 2,0 and 1 lone pairs of electrons respectively
• 1,1 and 1 lone pairs of electrons respectively
• 0,1 and 2 lone pairs of electrons respectively
• 1,0 and 2 lone pairs of electrons respectively

Solution

SF₄ molecule has 1 lone pair of electrons, CF₄ has no lone pair of electrons and XeF₄ has 2 lone pair of electrons respectively.

Q28. Which of the following has  maximum bond angle?

• CH₄
• H₂O
• NH₃
• CO₂

Solution

Maximum bond angle 180^° is possible for sp hybridization.

Q29. The spatial orientation of sp³d³ hybrid orbitals is:

• Square planar
• Octahedral
• Trigonal bi pyramidal
• Pentagonal bi pyramidal

Solution

The spatial arrangement of sp³d³ hybrid orbitals is pentagonal bi pyramidal.

Q30. Among H₂O, H₂S, H₂Se and H₂Te, the one with highest boiling point is:

• H₂O
• H₂Te
• H₂S
• H₂Se

Solution

Water has the highest boiling point because of the presence of hydrogen bonding in it.

Q31. Among the following maximum bond energy is present in:

• O₂
• O₂⁺
• O₂^-
• O₂^2-

Solution

The bond order of O₂⁺ is highest so the bond energy is highest in O₂⁺.

Q32. Which of these pairs of elements would be most likely to form an ionic compound?

• Cl and I
• Cl and Mg
• C and S
• Al and K

Solution

Ionic compounds will be formed more easily between the elements with comparatively low ionization enthalpy and elements with comparatively high negative value of electron gain enthalpy.

Q33. During hydrogen bonding in ammonia molecule, nitrogen atom is bonded to:

• Two hydrogen atoms
• Three hydrogen atoms
• Four hydrogen atoms
• One hydrogen atom

Solution

In ammonia molecule, nitrogen atom is bonded to three hydrogen atoms.

Q34. In PCl₅, the three P- Cl bonds in plane are called as

• Axial bonds
• Equatorial bonds
• Semi - planar bonds
• Sigma bonds

Solution

For molecules adopting trigonal bipyramidal geometry there are 5 bonds. The three bonds in the plane called planar bonds or equatorial bonds. And the remaining two bonds - one lying above the plane and one lying below the plane called axial bond.

Q35. The physical property that is not affected by hydrogen bonding is:

• Surface tension
• Viscosity
• Melting and boiling points
• Electronegativity

Solution

The electronegativity of an atom is not affected by hydrogen bond but it affects the formation of hydrogen bond.

Q36. The formation of a chemical bond is accompanied by:

• Increase in energy
• Decrease in energy
• Neither increase nor decrease in energy
• Sometimes increase and sometimes decrease in energy

Solution

Bond formation between two atoms occurs only when there is overall decrease in the energy of the system.

Q37. Identify an example of covalent solid:

• Sodium chloride
• Silicon carbide
• Methane
• Calcium chloride

Solution

Silicon carbide is an example of covalent solid.

Q38. Among the following species linear shape is found in:

• O₃
• NO₂^-
• SO₂
• NO₂⁺

Solution

NO₂⁺ has linear shape, due to sp hybrid state of N.

Q39. Which of the following statement is correct regarding covalent radius and van der Waals radius?

• van der Waals radius is equal to covalent radii
• van der Waals radius is always smaller than covalent radii
• van der Waals radius is always larger than covalent radii
• van der Waals radius is twice covalent radii

Solution

Covalent radius is half of the distance between two similar atoms joined by single covalent bond in same molecule. van der Waals radius is one half of the distance between two similar adjacent atoms belonging to two nearest neighbouring molecules of the same substance in the solid state. It is always larger than covalent radii.

Q40. Repulsive forces arise between:

• Nucleus of one atom and its own electron
• Nucleus of one atom and electron of other atom
• Electrons of two atoms
• Neutrons of two atoms