1. The formation of chemical bond is accomplished by:
(a) Decrease in energy
(b) Increase in energy
(c) Neither decrease nor increase in energy
(d) The repulsive forces overcoming the attractive forces
Explanation; (Answer; a)
A chemical bond is formed by an atom to get more stability. Every atom tries to get more stability by lowering its potential energy. This can be achieved by making a bond. The potential energy decreases when two atoms attract each other. Hence energy is liberated during the formation of a chemical bond i.e., it is an exothermic process.
2. Chemical bond formation takes place when:
(a) Forces of attractions overcome forces of repulsions
(b) Forces of attractions are equal to forces of repulsions
(c) Energy is absorbed
(d) Forces of repulsions overcome forces of attractions
Explanation; (Answer; a)
Chemical bond formation takes place when Forces of attractions overcome forces of repulsions.
The potential energy of the atoms is arbitrarily fixed as zero when there is no attraction between them. As the two atoms start overlapping with each other, the potential energy also decreases and reaches a minima (move your eye from right to left). The distance between the nuclei of two atoms at this point is called bond length. The forces of attraction between two atoms are maximum at this point.
However the potential energy starts increasing again if the atoms are bring more closer than this distance, since repulsion forces start dominating the forces of attractions.
3. Which one is correct reading ionic bond?
(a) It is formed by complete transference of electrons from one atom to another.
(b) It is an electrostatic force of attraction b/w two oppositely charged ions.
(c) It is formed b/w atoms of low IP and atoms of high EA.
(d) All of the above
Explanation; (Answer; d)
All options are correct.
4. Generally an ionic bond is formed b/w:
(a) Elements of group IA and IIA and elements of group VIA and VIIA.
(b) Elements of group VA and VIIA.
(c) Elements of group IA and VIIA.
(d) None of the above.
Explanation; (Answer; a)
Generally, an ionic bond is formed b/w atoms of low IP and atoms of high EA. These conditions are satisfied by elements of group IA and IIA and elements of group VIA and VIIA.
5. In which one of the following does ionic bonding occur between named atoms?
(a) Aluminium and chlorine in the tetrachloroaluminate ion.
(b) Boron and fluorine in boron trifluoride.
(c) Hydrogen and chlorine in hydrogen chloride.
(d) Hydrogen and sodium in sodium hydride.
Explanation; (Answer; d)
Generally, an ionic bond is formed b/w atoms of electropositive elements of low IP and atoms of electronegative element of high EA. The difference in electronegativity more than 1.7 is the deciding factor for ionic bond formation. Sodium and hydrogen with of 1.7 will form ionic bond in sodium hydride.
6. Which one is incorrect regarding ionic bond and Ionic compounds?
(a) Ionic bond is non-directional
(b) Ionic compounds are non-electrolytes and volatile
(c) Ionic compounds are hard and rigid solid
(d) Ionic compounds are soluble in polar solvent
Explanation; (Answer; b)
Due to strong electrostatic forces, ionic compounds are non-volatile. They are also electrolyte in molten or solution form.
7. Which one is incorrect regarding covalent bond and covalent compounds?
(a) covalent bond is non-directional.
(b) Covalent compounds are non-electrolytes and volatile.
(c) covalent compounds are soft and brittle.
(d) Covalent compounds are usually soluble in non-polar solvent.
Explanation; (Answer; a)
The meaning of covalent bonds being directional is that atoms bonded covalently prefer specific orientations in space relative to one another. As a result, molecules in which atoms are bonded covalently have definite shapes.
Ionic bond is non-directional, because charge is uniform in all direction. An ion is surrounded by other ion from all the direction. But covalent and coordinate bond are directional.as attraction is in a specific direction and at an angle relative to the bonding atoms.
8. Which one is correct about the effect of ionic character of covalent bond on the properties of compounds?
(a) Its elevates melting and boiling points.
(b) It increases the solubility of compounds in polar solvent (H2O)
(c) It shortens the bond distance thereby enhancing bond energies
(d) All of the above.
Explanation; (Answer; d)
All options are correct. The presence of ionic character of covalent bond increases the melting and boiling points, increases the solubility of compounds in polar solvents, increases the bond energy, shortens the bond length.
9. Which one is incorrect regarding bond energy?
(a) It is the amount of energy required to break one mole of bond to form isolated natural atom.
(b) It measures the strength of covalent bond.
(c) It increases with the increase in polarity.
(d) Bond energy of non-polar molecule is greater than that of polar molecule.
Explanation; (Answer; d)
Bond energy increases with increasing polarity. Hence, the bond energy of polar molecules are always greater than that of non-polar molecules.
10. Which statement is always true when two atoms join together by a covalent bond?
(a) One atom is a metal, the other atom is a non-metal
(b) One atom loses one electron, the other atom gains one electron
(c) The two atoms share one electron
(d) The two atoms share two electrons.
Explanation; (Answer; d)
A covalent bond is formed by the sharing of at least two electrons by bonded atoms.
11. A covalent bond is formed by
(a) Electron sharing between metals and non-metals
(b) Electron sharing between non-metals
(c) Electron transfer between non-metals
(d) Electron transfer from metals to non-metals
Explanation; (Answer; b)
A covalent bond is formed by mutual sharing of electrons between non-metals.
12. The shell of an atom with highest ‘n’ is known as:
(a) Valance shell
(b) Inner shell
(c) Empty shell
(d) Filled shell.
Explanation; (Answer; a)
Valance shell is the outermost shell of an atom with highest principal quantum number or ‘n’.
13. All inert gases except Helium are characterized by a completion of the outer ………
(a) s-orbital
(b) p-orbital
(c) d-orbital
(d) f-orbital
Explanation; (Answer; b)
All noble or inert gases have completely filled p-orbital except He.
14. Neutral atoms of Neon have the same number of electrons as each of the following EXCEPT:
(a) O–
(b) F1–
(c) Na1+
(d) Mg2+
Explanation; (Answer; a)
Neon has 10 electrons. All the ions given have 10 electrons except O– which has 9 electrons.
15. The attractive forces that holds an atom together in a molecule is termed as:
(a) Covalent bond
(b) Dative bond
(c) Chemical bond.
(d) Ionic bond
Explanation; (Answer; c)
The attractive forces that holds an atom together in a molecule is termed as chemical bond.
16. Chemical bond formation takes place due to interaction of …………electrons.
(a) Valance
(b) Inner
(c) Free
(d) Paired
Explanation; (Answer; a)
The interaction of valence electrons or unpaired electrons in the valance shell leads to bond formation between atoms.
17. Lower the energy…………. will be stability of molecules.
(a) Lesser
(b) Greater
(c) Both a and b
(d) None of the above
Explanation; (Answer; b)
Every system becomes stable when acquire less energy. The stability of molecules increases with the decreasing energy.
18. Inert gases have ……………….valance electrons.
(a) 5
(b) 4
(c) 7
(d) 8
Explanation; (Answer; d)
All noble gases or inert gases have 8 electrons in their valence shell expect He which has only two.
19. Which of the compounds have the ionic bond?
(a) NaCl
(b) KCl
(c) MgO
(d) All of the above
Explanation; (Answer; d)
Ionic compounds are formed between highly electropositive metallic elements of group IA and IIA with highly electronegative non-metallic elements of group VA, VI and VIIA. Moreover, the high electronegativity difference of more than 7 decides the ionic nature of compounds.
∆EN between Na and Cl in NaCl = 3 – 0.9 = 2.1
∆EN between K and Cl in KCl = 3 – 0.8 = 2.2
∆EN between Mg and O in MgO = 3.5 – 1.2 = 2.3
20. The mutual sharing of electrons pairs in atoms gives rise to:
(a) Hydrogen bond
(b) Ionic bond
(c) Covalent bond
(d) Dative bond
Explanation; (Answer; c)
Covalent bond is formed by the mutual sharing of one or more electron pairs between two bonded atoms of non-metallic elements.
21. Which molecule has covalent bond?
(a) NaCl
(b) CaCO3
(c) MgO
(d) HCl
Explanation; (Answer; d)
Non-metallic elements with electronegativity difference less than 1.7 form covalent bond. Both H and Cl are non-metals with ∆EN between them is 0.9.
22. Which type of bond is formed by mutual sharing of one electron pair b/w two bonded atoms?
(a) Single covalent
(b) Double covalent
(c) Triple covalent
(d) Ionic bond
Explanation; (Answer; a)
Single covalent involves mutual sharing of one electron pair or two electrons between bonded atoms. The monovalent atoms like H, F, Cl, Br and I can only form one single bond with other atoms.
23. Which molecule has single covalent bond?
(a) O2
(b) N2
(c) CO2
(d) CH4
Explanation; (Answer; d)
In CH4, carbon forms four single bond with 4 H atoms.
24. Which molecule does not have single covalent bond?
(a) NH3
(b) N2
(c) CCl4
(d) HF
Explanation; (Answer; b)
In N2, nitrogen atoms are triply bonded with each other.
25. Which molecule has double covalent bond?
(a) O2
(b) N2
(c) CCl4
(d) HF
Explanation; (Answer; a)
In O2, oxygen atoms are doubly bonded with each other.
26. Which molecule has triple covalent bond?
(a) C2H2
(b) N2
(c) CN−
(d) All of them
Explanation; (Answer; d)
Polyvalent atoms like C and N form triple bond.
27. Bond making is always:
(a) Endothermic
(b) Exothermic
(c) Both a and b
(d) None of the above
Explanation; (Answer; b)
Bond making is always exothermic releasing energy either in the form of lattice energy (ionic bond) or bond energy (covalent bond).
28. Bond breaking is always:
(a) Endothermic
(b) Exothermic
(c) Both a and b
(d) None of the above
Explanation; (Answer; a)
Bond breaking is always endothermic.
29. A covalent bond in which the shared electron pair is attracted equally by the two atoms is called:
(a) Polar bond
(b) Non- Polar bond
(c) dative bond
(d) hydrogen bond
Explanation; (Answer; b)
In Non- Polar bond, the shared electron pair is attracted equally by the two bonded atoms due to little or no difference in electronegativities.
30. Which one is incorrect regarding the examples of Non-Polar bond?
(a) S=C=S
(b) PH3
(c) CH4
(d) CH3Cl
Explanation; (Answer; d)
The difference in electronegativities in non-polar molecules is either zero or less than 0.5. In the ∆EN between C and Cl is 0.5, so C – Cl bond is polar.
31. A covalent bond in which the shared electron pair is attracted not equally by the two atoms is called:
(a) Polar bond
(b) Non- Polar bond
(c) dative bond
(d) hydrogen bond
Explanation; (Answer; a)
In Polar bond, the shared electron pair is attracted unequally by the two bonded atoms due to large difference in electronegativities.
32. Which molecule has greater bond energy?
(a) Polar molecule
(b) Non- Polar molecule
(c) None of the above
(d) All of the above.
Explanation; (Answer; a)
Polar molecules have greater bond energy due to the presence of polarity and partial ionic character.
33. Greater the difference in E N between bonded atoms …………..will be polarity.
(a) Lesser
(b) Greater
(c) None of the above
(d) All of the above.
Explanation; (Answer; b)
Polarity increases with the difference in E N between bonded atoms.
34. A bond is said to be 100% covalent, if it exists between atoms of:
(a) Same elements
(b) Different elements
(c) Same group
(d) Different group
Explanation; (Answer; a)
The non-polar bond is known as true covalent bond or 100% covalent bond lacking any ionic character and it exists between identical atoms of same elements.
35. The one sided sharing of electrons between two atoms produces, which type of bond?
(a) covalent bond
(b) hydrogen bond
(c) dative bond
(d) Ionic bond
Explanation; (Answer; c)
dative bond involves one-sided sharing of electrons between donor and acceptor atoms.
36. Which of the following has co-ordinate covalent bond?
(a) NH4+
(b) H2O
(c) H3O+
(d) Both a and c
Explanation; (Answer; d)
Coordinate covalent bond is usually found in compounds of N, O, Cl, S, P etc.
Examples of co-ordinate bond
O3, CO, N2O, H2O2, N2O3, N2O4, N2O5, SO2, SO3, HNO3, H3PO4, H3PO3, H2SO4, H4P2O7, HIO3, HClO4, HClO3, SO2Cl2, SOCl2, POCl3, Al2Cl6 (anhydrous), [AlCl4]−, CH3NO2, CH3NC, H3O+, NH4+, N2H5+, NO3−, SO42−, SO32−, CO32−, [Cu(NH3)4]2+ etc.
37. Which of the following has the shortest C−C bond length?
(a) C2H2
(b) C2H4
(c) C2H6
(d) C2H5OH
37. Explanation; (Answer; a)
Bond length varies inversely with bond order.
Since bond order of C2H2 is 3 (showing C≡C), the C – C bond length is shortest in C2H2.
38. Which of the following has the highest bond energy?
(a) C2H2
(b) C2H4
(c) C2H6
(d) C2H5OH
38. Explanation; (Answer; a)
Bond energy varies directly with bond order.
Since bond order of C2H2 is highest i.e. 3 (showing C≡C), the C – C bond energy is highest in C2H2.
39. Which one of the following bond has the most polar character?
(a) C–O
(b) C–Br
(c) C–F
(d) C–S
39. Explanation; (Answer; c)
The polarity of bond varies directly with difference in electronegativity of bonded atoms. Since C–F has the greatest ∆EN (1.5), it has the most polar character.
40. Which one of the following bond has the least polar character?
(a) C–H
(b) C–Cl
(c) C–O
(d) C–N
40. Explanation; (Answer; a)
The polarity of bond varies directly with difference in electronegativity of bonded atoms. Since C–H has the least ∆EN (0.4), it has the least polar character.
41. the degree or extent of polarity of a molecule is called:
(a) Bond energy
(b) Moment arm
(c) Dipole moment
(d) Ionic character
41. Explanation; (Answer; c)
Dipole moment is a measure of the degree or extent of polarity of a molecule. Greater the dipole moment, greater is the polarity and vice versa.
42. the product of magnitude of charge at each pole and the internuclear distance b/w the two opposite charges called:
(a) debye
(b) Moment arm
(c) Dipole moment
(d) Bond length
42. Explanation; (Answer; c)
Dipole moment is mathematically equal to the product of magnitude of charge at each pole and the internuclear distance b/w the two opposite charges.
43. Dipole moment is a:
(a) Scalar quantity
(b) Vector quantity
(c) Basic quantity
(d) None of the above
43. Explanation; (Answer; b)
Since dipole moment shows orientation of dipole in a particular direction, it is a vector quantity.
44. Dipole moment is denoted by:
(a) Double head arrow
(b) Double arrow
(c) Crossed tail arrow
(d) None of the above
44. Explanation; (Answer; c)
Since dipole moment is a vector quantity, it is denoted by crossed tail arrow (⇸) pointing towards negative pole.
45. dipole moment is defined as
(a) Charge x Internuclear distance
(b) Charge x Charge
(c) Charge x Debye
(d) Charge x Bond energy
45. Explanation; (Answer; a)
dipole moment is defined as the product of charge and internuclear distance.
46. S.I unit of dipole moment (µ) is
(a) N-sec
(b) N.m2
(c) C.m (coulomb x meter)
(d) None of the above
46. Explanation; (Answer; c)
Since dipole moment is equal to the product of charge (C) and internuclear distance (m), its SI unit is C.m (coulomb x meter). The cgs unit of dipole moment is e.s.u-cm which is called debye (D).
47. 1 coulomb is equal to:
(a) 2.99 x 109 e.s.u
(b)2.99 x 1019 e.s.u
(c)2.99 x 10‒19 e.s.u
(d)None of the above
47. Explanation; (Answer; a)
1 coulomb =2.99 x 109 e.s.u
48. 1 debye (1D) is equal to:
(a) 10‒30 coulomb-meter
(b)10‒18 e.s.u-cm
(c)10‒10 e.s.u-m
(d)All of the above
48. Explanation; (Answer; d)
Mathematically, dipole moment is the product of magnitude of charge at each pole and the inter-nuclear distance (bond distance) between two opposite charges.
Dipole moment (µ) = Charge x distance between two opposite charge
or
µ = e x d
where:
e = Charge at each pole (is of the order of 10–10 e.s.u. or 10–19 coulomb)
d = Distance between two opposite charges (is of the order of 10–8 cm or 10–10 m or 1 Å)
Therefore, dipole moment is of the order of 10–18 e.s.u-cm or 10–20 e.s.u-m (≈10–30 C-m) which is known as debye.
Thus if the product of charge and distance has a value of 3.34 x 10–30 C-m, the dipole moment has a value of 1 debye.
The unit debye is related to S.I. unit C-m as follows:
1 D = 3.34 x 10–30 C.m (1C = 2.99 x 109 e.s.u.)
49. the diatomic polar molecules have dipole moment:
(a) Equal to 0
(b)Greater than 0
(c)Equal to 1
(d)None of the above
49. Explanation; (Answer; b)
The diatomic polar molecules always have some dipole moment i.e. they have dipole moment greater than 0.
50. Which one has zero dipole moment?
(a) CO2
(b) CS2
(c) HCl
(d) Both a and b
50. Explanation; (Answer; d)
Dipole moment of linear molecules is zero. Both CO2 and CS2 have linear geometry. HCl being diatomic molecule has some dipole moment.
51. CO2 and CS2 has no dipole moment due to:
(a) Linear structure
(b) Angular structure
(c) Pyramidal structure
(d) Both a and b
51. Explanation; (Answer; a)
Dipole moment CO2 and CS2 has zero dipole moment due to their linear structure in which individual bond moments cancel out each other giving net zero dipole moment.
52. H2O and SO2 have dipole moment:
(a) Equal to 0
(b) Greater than 0
(c) Equal to 1
(d)None of them
52. Explanation; (Answer; b)
H2O and SO2 have dipole moment greater than 0 because both are angular molecules which always have some dipole moment.
53. H2O and SO2 have same dipole moment due to its:
(a) Bent structure
(b) Angular structure
(c) Both a and b
(d) None of the above
53. Explanation; (Answer; c)
Unsymmetrical polyatomic molecules like angular (bent), pyramidal, tetrahedral always have net value of dipole moment, thus such molecules are polar in nature. H2O, SO2, CH3Cl, NH3, etc. are polar molecules as they have some positive values of dipole moments.
54. the structure of triatomic molecule whose dipole moment is zero will be:
(a) Linear structure
(b) Angular structure
(c) Pyramidal structure
(d) Tetrahedral
54. Explanation; (Answer; a)
Symmetrical polyatomic molecules like linear, trigonal, symmetrical tetrahedral are not polar so they do not have any value of dipole moment.
55. tetrahedral molecules with symmetric structure have
(a) Zero dipole moment
(b) Some dipole moment
(c) Both a and b
(d) None of the above
55. Explanation; (Answer; a)
Symmetrical polyatomic molecules like linear, trigonal, symmetrical tetrahedral are not polar so they do not have any value of dipole moment.
56. CH4 and CCl4 have zero dipole moment due to:
(a) Symmetrical structure
(b) Unsymmetrical structure
(c) Both a and b
(d) None of the above
56. Explanation; (Answer; c)
Symmetrical polyatomic molecules like linear, trigonal, symmetrical tetrahedral are not polar so they do not have any value of dipole moment. CH4 and CCl4 have zero dipole moment due to symmetrical tetrahedral structure.
57. tetrahedral molecules with unsymmetrical structures have
(a) Zero dipole moment
(b) Some dipole moment
(c) Both a and b
(d) None of them
57. Explanation; (Answer; b)
Unsymmetrical polyatomic molecules like angular (bent), pyramidal, tetrahedral always have net value of dipole moment, thus such molecules are polar in nature. H2O, SO2, CH3Cl, CH2Cl2 and CHCl3, NH3, etc. are polar molecules as they have some positive values of dipole moments.
58. CH3Cl, CH2Cl2 and CHCl3 have some dipole moment due to
(a) Symmetrical structure
(b) Asymmetrical structure
(c) Both a and b
(d) None of the above
58. Explanation; (Answer; b)
CH3Cl, CH2Cl2 and CHCl3 have some dipole moment due to unsymmetrical tetrahedral structure.
59. the bond energy of hydrogen bond ranges
(a) 3 – 10 kcal
(b) 10 – 17 kcal
(c) 17 – 25 kcal
(d) 25 – 35 kcal
59. Explanation; (Answer; a)
Hydrogen bond is a secondary bond. Its bond energy ranges 3-10 kcal. the bond energy of hydrogen bonds is only 20-40 or 4-50 kJ/mol as compared to bond energy of 150–500 kJ/mol for normal covalent bond.
60. water boils at higher temperature than H2S due to
(a) Ionic bonding
(b) Covalent bonding
(c) London forces
(d) Hydrogen bonding
60. Explanation; (Answer; d)
Water being second most polar bond show extensive hydrogen bonding which leads to its high boiling point, high melting point, high specific heat etc. H2S does not hydrogen bonding due to its non-polar nature.
61. hydrogen bond greatly ……………… the solubility of compound
(a) Increases
(b) Decrease
(c) Has no effect
(d) Both a and b
61. Explanation; (Answer; a)
The solubility of compound increases in the presence of hydrogen bonding tendency of solvent with solute.
62. Ethyl alcohol is liquid while its isomer dimethyl ether is gas. This is b/c ethyl alcohol has
(a) Ionic bonding
(b) Covalent bonding
(c) Protonic Bridges
(d) London forces
62. Explanation; (Answer; c)
Ethyl alcohol is a polar molecule with terminal polarized hydrogen enable it to form hydrogen bonds with its own molecules. This leads to greater attractive forces in ethyl alcohol and hence ethyl alcohol is liquid. The dimethyl ether is an isomer of ethyl alcohol but it is gas at room temperature. This is due to the fact that dimethyl ether lacks polarized hydrogen and hence it cannot form hydrogen bond.
63. Hydrogen bond ……………. the m.p and b.p of compounds.
(a) Elevates
(b) Reduces
(c) Has no effect of
(d) Both a and b
63. Explanation; (Answer; a)
Water being second most polar bond show extensive hydrogen bonding which leads to its high boiling point, high melting point, high specific heat etc.
64. The bonding in sulphuric acid can be represented by the structure shown
How many electrons are involved in forming all the covalent bonds in one molecule?
(a) 6
(b) 8
(c) 12
(d) 16
64. Explanation; (Answer; d)
One single bond (shown by a line) represents 2 electrons. There are total 8 lines in the structure of sulphuric acid, so total 16 electrons (twice of lines) are involved in the formation of all the covalent bonds in its one molecule.
65. Outermost shells of two elements X and Y have two and six electrons respectively. If they combine, the expected formula of the compound will be
(a) XY
(b) X2Y
(c) XY2
(d) X2Y3
65. Explanation; (Answer; a)
Since X has only two valence electrons, it must be metallic element of group IIA which are divalent and lose two electrons to form divalent cation(X2+) and Y has six valence electrons, it must be a non-metallic element of group VIA which is bivalent and needs two electrons to complete its octet forming bivalent anion (Y2−). Hence the compound formed between X and Y must have formula of the type AB i.e. XY.
66. Intermolecular forces in solid hydrogen are
(a) Hydrogen bonds
(b) Covalent forces
(c) van der Waal’s forces
(d) All of these
66. Explanation; (Answer; c)
Solid hydrogen being non-polar can only have van der forces.
67. Which one of these is weakest?
(a) Ionic bond
(b)Covalent bond
(c) Metallic bond
(d) van der Waal’s forces
67. Explanation; (Answer; d)
van der Waal’s forces being secondary bonds or intermolecular forces has the weakest nature.
68. The nature of inter-particle forces in benzene is
(a) Dipole-dipole force
(b)Ion-dipole interaction
(c)Hydrogen bonding
(d) Dispersion forces
68. Explanation; (Answer; d)
Non-polar molecules have dispersion forces. Benzene being non-polar has only dispersion forces among its molecule.
69.Hydrogen bonding is not present in
(a) Water
(b)Glycerin
(c)Hydrogen fluoride
(d)Hydrogen sulphide
69. Explanation; (Answer; d)
Hydrogen bond is present in polar compounds containing polarized H. Hydrogen sulphide is non-polar due to small difference in electronegativities between S and H.
70. When two ice cubes are pressed over each other, they unite to form one cube. Which of the following forces is responsible to hold them together?
(a) Hydrogen bond
(b) van der Waal’s forces
(c) Dipole interaction
(d) Electrostatic forces
70. Explanation; (Answer; a)
The sticking of two ice cubes together is due to hydrogen bonding between different molecules of water.
71. Maximum hydrogen bonds in water are
(a) 4
(b) 3
(c) 2
(d) 1
71. Explanation; (Answer; a)
The maximum number of molecules that one water molecule can hold through hydrogen bonding is 4 because the two hydrogen atoms of water can form two hydrogen bonds and the two lone pairs on oxygen can also form two hydrogen bonds.
72. Ionic compounds have high melting points because of the strong attraction between oppositely charged ions. Which compound has the lowest melting point?
72. Explanation; (Answer; c)
Greater charge on cation and anion leads to greater polarization giving rise to high melting points. NaCl has the lowest melting point due to the least charges of their ions.
73. Which element exists as a macromolecule?
(a) Carbon
(b) Hydrogen
(c) Oxygen
(d)Sodium
73. Explanation; (Answer; a)
Carbon exists as macromolecule in the form of diamond and graphite.
74. In which solid can layers of atoms slide over each other?
(a) Diamond
(b) Graphite
(c)Haematite
(d)Silica
74. Explanation; (Answer; b)
Graphite has layered structure having weak van der Waal’s forces between layers allowing layers to slide over each other.
75. How many electrons are used in covalent bonding in the N2 molecule?
(a)2
(b)4
(c)6
(d)10
75. Explanation; (Answer; c)
The N atoms in N2 molecules is linked through triple bond involving sharing of 3 pairs of electrons or total 6 electrons.
76. Hydrogen chloride gas has
(a)Hydrogen bond
(b)Ionic bond
(c)Covalent bond
(d)Double bond
76. Explanation; (Answer; c)
Gases have only covalent bonds. In addition, HCl contains both non-metallic atoms, which can only form covalent bonds.
77. Which of the following has maximum ionic character?
(a)LiCl
(b)KCl
(c)CsCl
(d)NaCl
77. Explanation; (Answer; c)
According to the Fajan's rule, smaller the cation, bigger the anion, more is the covalent character. On the other hand, bigger cation, in the given case, will favor ionic character, as the anion is same for all.
Here, Cs+ is the biggest cation. Hence, CsClwill have maximum ionic character.
78. Which of the following have same number of electrons in the outermost orbit?
(a) Pb, Sb
(b) As, Bi
(c) N, O
(d) P, Ca
78. Explanation; (Answer; b)
Elements of same group have same number of electrons in their outermost shell. As and Bi are the members of group VA and both have 5 valence electrons.
79. Which of the following is most electronegative?
(a) Lead
(b) Silicon
(c) Carbon
(d) Tin
79. Explanation; (Answer; c)
Down the group in the parodic table, electronegativity decreases. C, Si, Ge, Sn and Pb are present in group IVA. Carbon being the first member has the highest electronegativity while Pb being the last congener of this group is least electronegative.
80. Higher the bond order greater is
(a)Paramagnetism
(b)Bond angle
(c)Bond energy
(d)Bond length
80. Explanation; (Answer; c)
Bond order is inversely related with bond energy.
81. Oxygen-oxygen bond length in ozone is same because of
(a)Hyper conjugation
(b)Covalent & ionic bond
(c)Resonance
(d)Refraction
81. Explanation; (Answer; c)
The presence of same bond lengths between two different bonds of two atoms indicates resonance.
82. The number of electron pairs that are shared between two atoms having a triple bond are
(a)2
(b)6
(c)5
(d)3
82. Explanation; (Answer; d)
triple bond involving sharing of 3 pairs of electrons or total 6 electrons.
83. Resonance is not shown by
(a)Carbon dioxide
(b)Benzene
(c)Carbonate ion
(d)Silicon dioxide
83. Explanation; (Answer; d)
Resonance is shown by those compounds containing double bonds. Silicon dioxide contains only single bonds.
84. Amongst HX, the maximum dipole moment is of
(a)HBr
(b)HF
(c)HI
(d)HCl
84. Explanation; (Answer; a)
Dipole moment is directly proportional to the polarity of molecule, which in turn is proportional to the ∆EN. The HF has most polar covalent bond due to greatest ∆EN (1.9).
85. The bond angle in the ammonium ion is equal to
(a)90o
(b)104o
(c)120o
(d)109o.28
85. Explanation; (Answer; d)
ammonium ion (NH4+) is AB4 type specie whose shape must be tetrahedral with bond angel of 109o.28.
86. What is the total number of electrons in the correct Lewis dot formula of the sulfite ion?
(a)8
(b)24
(c)30
(d)26
86. Explanation; (Answer; d)
The total number of valence electrons in the correct Lewis dot formula of the sulfite ion is 6 + 3(6) + 2 = 26. S atom has 6 valence electrons. Also each O atom has 6 valence electrons. Two additional electrons are present due to two negative charges.
87. Which of the following pairs of elements and valence electrons is incorrect?
(a)Al = 3
(b)Br = 7
(c)S = 4
(d)Sr = 2
87. Explanation; (Answer; c)
Group number of an element represent its valence electrons. Sulphur being a member of group VIA should contain 6 valence electrons not 4.
88. Which of the following does not have a noble gas electron configuration? (or Which of the following is not isoelectronic with a noble gas?)
(a)S2‒
(b)Ba+
(c)Sb3‒
(d)Sc3+
88. Explanation; (Answer; b)
Ba+contains only 55 electrons (not 54) and it does not have a noble gas electronic configuration.
89. The electronic structure of the SO2 molecule is best represented as a resonance hybrid of ……….. equivalent structures.
(a)2
(b)3
(c)4
(d)5
89. Explanation; (Answer; a)
The electronic structure of the SO2 molecule is best represented as a resonance hybrid of two equivalent structures. SO2 molecule has two different types of pi bonds (pπ− pπ) and (pπ− dπ). But even then both of S−O bonds are identical. Hence, SO2 molecule is resonance hybrid of two structures.
90. Which one of the compounds below is most likely to be ionic?
(a)Gas
(b) ScCl3
(c)ClO2
(d) NO2
90. Explanation; (Answer; b)
Ionic bond is formed between metals and non-metals. Sc is a transition metal.
91. In the Lewis structure for the OF2 molecule, the number of lone pairs of electrons around the central oxygen atom is
(a)0
(b) 1
(c)2
(d) 3
91. Explanation; (Answer; c)
The number of lone pairs of electrons around the central atom of group VA (N, P, etc.) = 1
The number of lone pairs of electrons around the central atom of group VIA (O, S, etc.) = 2
The number of lone pairs of electrons around the central atom of group VIIA (F, Cl, etc.) = 3
92. Which one of the following violates the octet rule?
(a)PCl3
(b) NF3
(c)AsF5
(d) OF2
92. Explanation; (Answer; c)
Elements of group VA like N, P, As etc. violate the octet rule when they show their highest oxidation state of +5 forming AB5 type like compounds. AsF5 violates the octet rule having 10 electrons around central As atom.
93. The molecular formula of the compound formed from ‘B’ and ‘C’ will be
(a)BC
(b) B4C3
(c)BC2
(d) BC3
93. Explanation; (Answer; b)
B is trivalent and C is tetravalent. The compound formed between B and C should be B4C3 (their valencies are cross multiplied).
94. The bond between ‘B’ and ‘C’ will be
(a)Covalent
(b)Hydrogen
(c)Coordinate
(d)Ionic
94. Explanation; (Answer; a)
B is a metalloid and C is a non-metal. The compound formed between two non-metals or metalloid and non-metal is covalent.
95. Which one of the following species contains a polar covalent bond?
(a)Carbon dioxide
(b)Magnesium fluoride
(c)Sodium chloride
(d)Oxygen
95. Explanation; (Answer; a)
C=O bond in carbon dioxide is polar. But the overall molecule of CO2 is non-polar due to zero dipole moment owing to linear structure.
96. What is the formula of the ion formed when potassium achieves noble-gas electron configuration?
(a)K2+
(b)K1−
(c)K+
(d)K2−
96. Explanation; (Answer; c)
Potassium (K) is an alkali metal of group IA with electronic configuration [Ar], 4s1 showing that it has only one valence electrons. K loses its single valence electron to form monovalent cation K+ to achieve noble gas stable electronic configuration.
97. Which of the following ions has a pseudo-noble-gas electron configuration?
(a)Fe2+
(b)Cu+
(c)Mn2+
(d)Ni+
97. Explanation; (Answer; b)
An element with pseudo noble gas configuration has 18 electrons in the outermost shell instead of 8.
EC of Cu+ = [Ar], 3d10 (pseudo inert gas configuration).
98. How many valence electrons are transferred from the nitrogen atom to potassium in the formation of the compound potassium nitride?
(a)3
(b)2
(c)2
(d)0
98. Explanation; (Answer; a)
Nitrogen is trivalent having 5 valence electrons and needs 3 electrons to complete its octet. Hence one N atom gives 3 electrons to three potassium atoms in the formation of the ionic compound potassium nitride.
99. Which of the following elements, if placed as the central atom in a molecule, is capable of having more than eight valence electrons?
(a)N
(b) Te
(c)F
(d)O
99. Explanation; (Answer; b)
N, F and O are elements of period 2 which cannot expand their octet due to lack of d-orbitals. Te being a transition metal, can expand its octet.
100. The valence shell of element ‘A’ contains 3 electrons while the valence shell of element ‘B’ contains 6 electrons. If ‘A’ combines with ‘B’, the probable formula of the compound formed will be
(a) AB2
(b) A2B
(c)A2B3
(d)A3B2
100. Explanation; (Answer; c)
The element A is trivalent with EC ns2 np1 and the element B is bivalent with EC ns2 np4. They can form compound of the type A2B3
101. Which compound has the greatest total number of lone pairs of electrons in the valence shell of all of its atoms?
(a) CH3Cl
(b) CO2
(c) N2H4
(d) NH4CN
101. Explanation; (Answer; b)
The number of lone pairs of electrons around the central atom of group VA (N, P, etc.) = 1
The number of lone pairs of electrons around the central atom of group VIA (O, S, etc.) = 2
The number of lone pairs of electrons around the central atom of group VIIA (F, Cl, etc.) = 3
(a) The number of lone pairs of electrons in CH3Cl = 3
(b) The number of lone pairs of electrons in CO2 = 4 (one O has 2 lone pairs)
(c) The number of lone pairs of electrons in N2H4 = 2 (One N has one lone pair)
(d) The number of lone pairs of electrons in NH4CN = 2 (One N has one lone pair)
102. Which one of the following pairs of atoms would form a non-polar covalent bond?
(a) C and O
(b) N and O
(c) Cl and Cl
(d) Na and Cl
102. Explanation; (Answer; c)
The bond between identical atoms is always polar. So Cl–Cl bond must be non-polar.
103. Which one of the following elements has valence electrons in the n = 3 shell?
(a) Beryllium
(b) Silicon
(c) Oxygen
(d) Neon
103. Explanation; (Answer; b)
EC of 14Si is [Ne], 3s2 3p2 shows that its valence electrons lies in 3rd orbit (n=3).
104. Which one of the following species contains an unpaired electron?
(a) N2
(b) NO31‒
(c) N2O4
(d) NO2
104. Explanation; (Answer; d)
NO2 is an odd electron molecules has only 7 valence electrons around it.
105.Which of the following pairs do not form a coordinate covalent bond with each other?
(a) NH3 and H+
(b) H2O and H+
(c) NH3 and BF3
(d)CH4 and AlCl3
105. Explanation; (Answer; d)
Carbon cannot form coordinate covalent bond due to lack of lone pair and empty orbital.
106.Majority of the compounds in nature are:
(a) Electrovalent
(b) Ordinary covalent
(c) Dative covalent
(d) Hydrogen bond
106. Explanation; (Answer; b)
Majority of the compounds in nature are Ordinary covalent
107.Which one of the following is the most polar molecule?
(a) C2H5OH
(b) CH3Br
(c) H2O2
(d) SO2
107. Explanation; (Answer; c)
Most polar molecule must have highest EN difference. In H2O2, EN difference is highest so it has the most polar bond.
108. The percentage of ionic character in NaCl is
(a) 92%
(b) 82%
(c) 72%
(d) 78%
108. Explanation; (Answer; c)
The percentage of ionic character in NaCl is 72%
109. Dipole moment is zero if geometry is
(a) Triangular planar
(b) Linear
(c) Trigonal bipyramidal
(d) All of these
109. Explanation; (Answer; d)
Dipole moment is zero if geometry is linear, trigonal, tetrahedral and bipyramidal.
110. Number of shared electron pairs in ethane are
(a) 5
(b) 6
(c) 7
(d) 8
110. Explanation; (Answer; c)
There are 7 sigma bonds in ethane, C2H6. Hence the number of shared electrons pairs is 7.
111. Hydrogen bonding involves in
(a) Biological molecules
(b) Paints
(c) Solubility
(d) All of these
111. Explanation; (Answer; d)
Hydrogen bonding is involved in all given options.
112. Coordinate covalent bond is present in
(a) N2H5+
(b) [AlCl4]−
(c) O3
(d) All of these
112. Explanation; (Answer; d)
Examples of co-ordinate bond
O3, CO, N2O, H2O2, N2O3, N2O4, N2O5, SO2, SO3, HNO3, H3PO4, H3PO3, H2SO4, H4P2O7, HIO3, HClO4, HClO3, SO2Cl2, SOCl2, POCl3, Al2Cl6 (anhydrous), [AlCl4]−, CH3NO2, CH3NC, H3O+, NH4+, N2H5+, NO3−, SO42−, SO32−, CO32−, [Cu(NH3)4]2+ etc.
113. Which of the following is an element as well as covalent compound?
(a) Iodine
(b) Table salt
(c) Diamond
(d) Silica
113. Explanation; (Answer; c)
Diamond is a macromolecular substance. It is an element as well as covalent compound.
114. Coordinate covalent bond is present in
(a) SO2
(b) [Cu(NH3)4]2+
(c) POCl3
(d) All of these
114. Explanation; (Answer; d)
Examples of co-ordinate bond
O3, CO, N2O, H2O2, N2O3, N2O4, N2O5, SO2, SO3, HNO3, H3PO4, H3PO3, H2SO4, H4P2O7, HIO3, HClO4, HClO3, SO2Cl2, SOCl2, POCl3, Al2Cl6 (anhydrous), [AlCl4]−, CH3NO2, CH3NC, H3O+, NH4+, N2H5+, NO3−, SO42−, SO32−, CO32−, [Cu(NH3)4]2+ etc.
115. The maximum number of electron with clock-wise spin that can be accommodated in “N” shell is
(a) 32
(b) 18
(c) 16
(d) 8
115. Explanation; (Answer; c)
The maximum number of electrons in ‘N’ shell is 32 (2n2). Since electrons are always in pair in orbitals with opposite spins. Hence half electron have clock-wise spin and other half have anti-clock wise spin i.e. 16 electrons out of 32 have clock-wise spins and other 16 have anti clock-wise spins.
116. The most paramagnetic element is
(a) Manganese
(b) Cobalt
(c) Iron
(d) Chromium
116. Explanation; (Answer; c)
When placed in a magnetic field, paramagnetic materials tend to become weakly magnetized in the direction of the magnetizing field. Most atoms or ions with incompletely filled atomic orbitals are paramagnetic due to the presence of unpaired electrons in the substance. Unpaired electrons have a magnetic dipole moment and act like small magnets because of their spin.
The atom with greater number of unpaired electron will be most paramagnetic.
Electronic Configuration of Manganese... [Ar] 3d5 4s2 (5 unpaired electrons)
Electronic Configuration of Cobalt …… [Ar] 3d7 4s2 (3 unpaired electrons)
Electronic Configuration of Iron ……… [Ar] 3d6 4s2 (4 unpaired electrons)
Electronic Configuration of Chromium …… [Ar] 3d5 4s1 (6 unpaired electrons)
Chromium has 6 unpaired electrons in its d orbital. So, it will show maximum Paramagnetism.
117. Which among the following have triple bonds?
(I) NO3− (II) HCN (III) CO (IV) CH3CN
(a) I, II and III only
(b) I, II and IV only
(c) II, III and IV only
(d) I, III and IV only
117. Explanation; (Answer; c)
HCN………… H – C ≡N
CO ………….. C ≡O
CH3CN……. CH3 –C ≡N
118. Among the following the lowest degree of Paramagnetism per mole of the compound at 298 K will be shown by
(a) MnSO4.4H2O
(b) CuSO4.5H2O
(c) FeSO4.6H2O
(d) NiSO4.6H2O
118. Explanation; (Answer; b)
Valence Shell EC of Mn2+ of ion = 3d5 (5 unpaired electron)
Valence Shell EC of Cu2+ of ion = 3d9 (1 unpaired electron)
Valence Shell EC of Fe2+ of ion = 3d6 (4 unpaired electron)
Valence Shell EC of Ni2+ of ion = 3d8 (2 unpaired electron)
Least Paramagnetism is shown by that specie which contains least number of unpaired electrons. Hence CuSO4.5H2O with least number of unpaired electron exhibit lowest degree of Paramagnetism.
119.The most suitable method of the separation of a mixture of ortho and para-nitrophenol mixed in the ratio of 1:1 is
(a) Crystallization
(b) Colour spectrum
(c) Vaporization
(d)Distillation
119. Explanation; (Answer; d)
Ortho and para-nitrophenols are separated by steam distillation because ortho-nitrophenol is steam volatile while para-nitrophenol is not.
In ortho and para-nitrophenol, ortho-nitrophenol has intramolecular H-bonding. So, it has lower boiling point and is more volatile and hence is steam distillable. Intermolecular H-bonding is more stronger then intramolecular H-bonding.
Whereas para-nitrophenol exist as assoicated molecuels due to intermolecular H-bonding and has higher boiling point. Due to difference in boiling points ortho and para-nitrophenol can be separated from each other by distillation.
120. Which of the following hydrides has the lowest boiling point?
(a) H2O
(b) H2S
(c) H2Se
(d)H2Te
120. Explanation; (Answer; b)
H2O > H2S < H2Se > H2Te
H2S has lowest boiling point and H2O has highest boiling point due to hydrogen bonding.
From H2S to H2Te, the boiling points increase with increase in molecular weights, due to the increase in van der Waal's forces with molecular mass.
However, boiling point of H2O>H2S even though H2O has lower molecular mass than H2S, due to the intermolecular hydrogen bonding in water that is not present in H2S and other hydrides in Group VIA.
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