MUNISH KAKAR’s INSTITUTE OF CHEMISTRY
MOLECULAR ORBITAL THEORY ( WS #9 )
Q1.
Which of the following pairs of molecule can exist?
(a) He2 and Be2
Q2.
(b) O22 and Na2
(c) O22 and H 22
(d) Be2 and Mg2
Which of the following statements is not correct regarding bonding molecular orbitals?
(a) Bonding molecular orbitals possess less energy than the atomic orbitals from which
they are formed.
(b) Bonding molecular orbitals have low electron density between the two nuclei
(c) Electron in bonding molecular contributes to the attraction between atoms
(d) They are formed when the lobes of the combining atomic orbitals have the same sign
Q3.
Which among the following is/are true regarding molecular orbital ?
(VI) For given subshell energy of BMO is larger than energy of ABO
(VII) In BMO, electron density between two nuclei is maximum
(VIII) In ABO , electron density between two nuclei is minimum
(IX) BMO is a result of positive overlap
(X)
ABO is a result of positive overlap
(a) I , II , IV
Q4.
(d) p-p > s-s > p-s
(b) 2
(c) 3
(d) 4
(b) O 22 
(c) F 22 
(d) H 2
(b) O 2
(c) O 22 
(d) H 2
The bond order in O 2 is the same as in :
(a) N 2
Q9.
(c) p-p > p-s > s-s
The species which does not show paramagnetism is :
(a) O2
Q8.
(b) s-s > p-s > p-p
Which of the following has fractional bond order ?
(a) O 22 
Q7.
(d) III , V
How many unpaired electrons are present in N 2 ?
(a) 1
Q6.
(c) II , III , IV
The strength of bonds formed by 2s-2s, 2p-2p and 2p – 2s overlap has the order:
(a) s-s > p-p > p-s
Q5.
(b) I , III , V
(b) CN-
(c) CO
(d) NO+
In the formation of N 2 the electron is lost from :
(a) a σ-orbital
(b) a π-orbital
(c) a σ*-orbital
(d) a π* -orbital
(c) C2, N2, F2
(d) B2, O 22  , N2
Q10. The diamagnetic molecule are :
(a) B2, C2, N2
(b) O2, N2, F2
Q11. In which of the following processes, the value of magnetic moment does not change ?
(a) N2 
 N2
(b) N2 
 N2
(c) O2 
 O2
(d) O2 
 O2
Q12. When N2 is formed form N2, bond order __ and when O2 is formed from O2, bond order __
(a) increases
(b)decreases
(c)increases, decreases (d) decreases, increases
S.C.O. No. 203, SECOND FLOOR, SECTOR 14, PANCHKULA. Phone : 9417655033, 9888019721
MUNISH KAKAR’s INSTITUTE OF CHEMISTRY
Q13. Which of the following has identical bond order ? (I) CN
(a) I, III
(b) II, IV
(II) O2
(c) I, II, III
(III) NO+
(IV) CN+
(d) I, IV
Q14. The common features among the species CN–, CO and NO+ is/are
(a) are isoelectronic
(b) bond order three
(c) both a and b
(d) neither a nor b
Q15. N2 and O2 are converted to monocations N

2
and O

2
respectively, which is wrong
statement:
(a) In N 2 , the N-N bond weakens
(b) In O 2 , the O-O bond order increases
(c) In O 2 , the paramagnetism decreases (d) N 2 becomes diamagnetic
Q16. According to molecular orbital theory, which of the following statements about the

magnetic character and bond order is correct for O 2 ?
(a) Paramagnetic, B.O. < O2
(b) Paramagnetic, B.O. > O2
(c) diamagnetic, B.O. < O2
(d) diamagnetic, B.O. > O2
Q17. On changing N2 to N2+, the dissociation energy of N-N bond ….. and on changing O2 to O2+
the dissociation energy of O-O bond ……
(a) increases, decreases
(b) decreases, increases
(c) decreases in both cases
(d) increases in both cases
Q18. Which of the following species have the same bond order ?
(I) CO
(II) CN-
(III) O2+
(IV) NO+
(a) I, II, III
(b) I, II, IV
(c) I, III, IV
(d) II, III, IV
Q19. Which of the following is paramagnetic ?
(a) CO
(b) O 2
(c) CN 
(d) NO+
Q20. Which of the following species contain unpaired electron(s) ?
(a) CN-
(b) CN+
(c) NO+
(d) NO-
Q21. Which of the following statements is false?
(a) N2 has greater dissociation energy than N2+
(c) O22- is paramagnetic
(b) O2 has lower dissociation energy than O2+
(d) O22- is diamagnetic
Q22. O2 molecule is
(a) paramagnetic
(b) diamagnetic
(c) ferromagnetic
(d) none of these
(c) 2.33
(d) 2.5
Q23. The bond order of O 2 is
(a) 0.5
(d) 1.5
Q24. Antibonding MO is formed by
(b) Addition of atomic orbitals
(c) Constructive overlap of atomic orbitals
(b) Destructive overlap of atomic orbitals
(d) Division of atomic orbitals
S.C.O. No. 203, SECOND FLOOR, SECTOR 14, PANCHKULA. Phone : 9417655033, 9888019721
MUNISH KAKAR’s INSTITUTE OF CHEMISTRY
Q25. Peroxide ion will have bond order ;
(a) lower than O2
(b) higher than O2
(c) equal to O2
(d) equal to NO 
Q26. Which among the following species is paramagnetic ?
(a) F2
(b) O2
(c) N2
(d) super oxide ion
Q27. Which among the following will have highest bond order ?
(a) O2
(b) O2
(c) O22
(d) O22
Q28. Which among the following is true ?
(a) When N 2 is converted to N 2 , bond dissociation energy increases
(b) When O2 is converted to O2 , bond dissociation energy decreases
(c) When N 2 is converted to N 2 , bond bond length increases
(d) When O2 is converted to O2 , bond bond length increases
Q29. Which is more stable in between N 2 and O2 ?
(a) former
(b) latter
(c) both have same stability
(d) can not be compared
Q30. Which among the following specie is paramagnetic in nature ?
(a) O2
(b) O2
(c) O22
(d) O22
Q31. Which among the following has largest Cl – O bond order ?
(a) ClO21
(b) ClO41
(c) ClO31
(d) ClO 1
Q32. The bond order of N 2 is equal to that of :
(a) O2
(b) O22
(c) O2
(d) none
Q33. Which among the following pairs contain both paramagnetic species.
(a) O22 and N 2
(b) O2 and N2
(c) O2 and N2
(d) O2 and N 2
Q34. Which of the following statements is true according to M.O.T. :
(a) Higher the bond order lesser the bond length
(b) Higher the bond order greater the bond length
(c) Higher the bond order lesser the bond energy
(d) Higher the bond order lesser the number of bonds
Q35. Which among the following species is diamagnetic in nature ?
a) He2
b) H 2
c) H 2
d) H 2
Q36. If X – axis is considered to be inter nuclear axis , which among the following overlap will
give rise to  molecular orbital ?
(a) s  px
(b) p y  p y
(c) px  px
d) all of these
S.C.O. No. 203, SECOND FLOOR, SECTOR 14, PANCHKULA. Phone : 9417655033, 9888019721
MUNISH KAKAR’s INSTITUTE OF CHEMISTRY
Q37. The correct order of increasing C-O bond strength of CO, CO32-, CO2 is:
(a) CO 32  < CO2 < CO
(b) CO2 < CO 32  < CO
(c) CO < CO 32  < CO2
(d) CO < CO2 < CO 32 
Q38. In PO 34 , the normal charge on each oxygen atom and the PO bond order respectively
are:
(a) – 0.75e, 0.6
(b) – 0.75e, 1.0
(c) – 0.75e, 1.25
(d) – 3e, 1.25
Q39. Among the molecules/species O2 , O2[AsF4] and KO2, the correct order of increasing bond
length of oxygen -oxygen bond is :
(a) O2 < KO2 < O2[AsF4]
(b) O2[AsF4] < O2 < KO2
(c) KO2 < O2 < O2[AsF4]
(d) O2[AsF4] < KO2 < O2

Q40. Which among the following specie has 2C  3 e bond ?
(a) O2
(b) O2
(c) O22
(d) O22
SUBJECTIVE SECTION
Q41. Draw molecular orbital diagram of given species O2 , O2 ( super oxide) & O22 (peroxide )
Electronic configuration of O2 = 12s , 1s2 ,  22s ,  2s2 ,  22pz ,  22px   22py ,  21px   2 p0y
Electronic configuration of O2 = 12s , 1s2 ,  22s ,  2s2 ,  22pz ,  22px   22py ,  21px   2 p2y
Electronic configuration of O22  = 12s , 1s2 ,  22s ,  2s2 ,  22pz ,  22px   22py ,  2 p2x   2 p2y

Q42. Draw shapes of given molecular orbitals ;  2 pz ,  2 pz ,  2 px ,  2 p y ,  2s and  2s
Q43. Why Li2 is known while Be2 is not known ?
Li2 has bond order =1 , while Be2 has bond order = 0
Q44. Why Ne2 molecule or He2 does not exist ?
Both Ne2 and He2 have bond order = 0
Q45. Why bond strength of nitrogen -nitrogen bond in N 2 is larger than oxygen - oxygen bond
in O2 ?
Both N 2 and O2 have same bond order, yet in N 2 less number of electrons occupy
anit-bonding molecular orbitals in comparison to O2
S.C.O. No. 203, SECOND FLOOR, SECTOR 14, PANCHKULA. Phone : 9417655033, 9888019721