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1 . Isostru ctural species are th ose which h ave the s ame s ha pe an d h ybridisation.Amon g the given species identify the isostru ctu ral pa irs.

(i) [NF3

and BF3]

(ii) [BF4

an d NH

4

+]

(iii) [BCl3

an d BrCl3]

(iv) [NH3

an d NO3

]

2 . Polarity in a molecu le an d h ence th e dipole mom ent d epend s pr ima rily on

electronegat ivity of th e con stitu ent a toms an d sh ap e of a molecule. Wh ich of

th e following h as th e highest d ipole mom ent?

(i) CO2

(ii) HI

(iii) H2O

(iv) SO2

3 . Th e types of h ybrid orbitals of n itrogen in NO2

+, NO

3

and NH

4

+resp ectively a re

expected t o be

(i) s p , s p 3 an d s p2

(ii) s p , s p 2 an d s p3

(iii) s p 2 , s p an d s p3

(iv) s p 2 , s p 3 an d s p

4 . Hydr ogen bon ds a re formed in ma ny comp oun ds e .g., H2O, HF, NH

3. Th e

boil in g point of su ch compou n ds d epend s to a large exten t on th e stren gthof hydrogen b ond an d th e nu mb er of hydrogen bon ds. The correct decreasing

order of the b oilin g points of ab ove compou n ds is :

(i) HF > H2O > NH

3

I. Multiple Choice Questions (Type-I)

CHEM ICCHEM ICCHEM ICCHEM ICCHEM ICAL BONDING ANDAL BONDING ANDAL BONDING ANDAL BONDING ANDAL BONDING AND

M OLECULM OLECULM OLECULM OLECULM OLECULA R SA R SA R SA R SA R STRUCTRUCTRUCTRUCTRUCTURETURETURETURETURE

CHEM ICCHEM ICCHEM ICCHEM ICCHEM ICAL BONDING ANDAL BONDING ANDAL BONDING ANDAL BONDING ANDAL BONDING AND

M OLECULM OLECULM OLECULM OLECULM OLECULA R SA R SA R SA R SA R STRUCTRUCTRUCTRUCTRUCTURETURETURETURETURE

U nitU nitU nitU nitU nit

44

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4 0Exemplar Problems, Chemis t ry

(ii) H2O > HF > NH

3

(iii) NH3> HF > H

2O

(iv) NH3> H

2O > HF

5 . In PO4

3 ion th e forma l ch arge on th e oxygen a tom of PO bond is

(i) + 1

(ii) 1

(iii) 0 .7 5

(iv) + 0 .75

6 . In NO3

ion , the n u mb er of bond pairs a nd lone pa irs of electrons on nitrogen

atom are

(i) 2 , 2

(ii) 3 , 1

(iii) 1 , 3

(iv) 4 , 0

7 . Wh ich of th e followin g species ha s tet ra h edra l geometr y?

(i) BH4

(ii) NH2

(iii) CO3

2

(iv) H3O

+

8 . Nu mber of bonds a n d bon ds in t he following str u ctu re is

(i) 6, 19

(ii) 4, 20

(iii) 5, 19

(iv) 5 , 20

9 . Wh ich m olecu le/ ion ou t of th e following does not conta in u npa ired electrons?

(i) N2

+

(ii) O2

(iii) O2

2

(iv) B2

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4 1 Chemical Bonding and Molecular St ructure

1 0 . In which of th e following m olecule/ ion all th e bond s a re n o t equal?

(i) XeF4

(ii) BF4

(iii) C2H

4

(iv) SiF4

1 1 . In which of th e following s u bs tan ces will hydrogen b ond be s trongest?

(i) HCl

(ii) H2O

(iii) HI

(iv) H2S

1 2 . If th e electron ic configur at ion of an elem ent is 1 s 2 2 s2 2p6 3s 2 3p 6 3d2 4s2 , the

fou r electron s involved in ch emical b ond form at ion will be_____.

(i) 3p6

(ii) 3p6 , 4s 2

(iii) 3p6 , 3d2

(iv) 3 d2, 4 s2

1 3 . Which of th e followin g an gle corresp ond s t o s p 2 hybridisation?

(i) 9 0

(ii) 1 2 0

(iii) 1 80

(iv) 1 0 9

The e lect ronic con f igurat ions of three e lem ent s, A, B and C are given below.

Answer the quest ions 1 4 to 1 7 on th e bas is o f these c onf igurat ions .

A 1 s 2 2 s 2 2p6

B 1 s 2 2 s 2 2p6 3 s 2 3p3

C 1 s 2 2 s 2 2p6 3 s 2 3p5

1 4 . Sta ble form ofA ma y be represented b y the formu la :(i) A

(ii) A2

(iii) A3

(iv) A4

1 5 . Sta ble form ofC ma y be represented by th e formu la :

(i) C

(ii) C2

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(iii) C3

(iv) C4

1 6 . The m olecular form u la of th e compou nd formed from B an d C will be

(i) BC

(ii) B2C

(iii) BC2

(iv) BC3

1 7 . Th e bond between B an d C will be

(i) Ion ic

(ii) Cova len t

(iii) Hyd r ogen

(iv) Coor din a t e

1 8 . Which of th e followin g order of energies of m olecula r orb itals of N2

is correct?

(i) (2py

) < (2pz) < (*2p

x) (*2p

y)

(ii) (2py

) > (2pz) > (*2p

x) (*2p

y)

(iii) (2py

) < (2pz) > (*2p

x) (*2p

y)

(iv) (2py

) > (2pz) < (*2p

x) (*2p

y)

1 9 . Wh ich of th e followin g st atem ent is not correct from th e view point of m olecularorbital theory?

(i) Be2 is not a sta ble molecule.

(ii) He2

is n ot s table but He2

+is expected to exist.

(iii) Bon d s t r en gt h o f N2is ma ximu m am ongst the homonu clear dia tomic

molecu les b elongin g to the s econ d p eriod.

(iv) The order of energies of molecular orbita ls in N2

molecu le is

2 s < * 2s < 2pz

< (2px

= 2py

) < (*2px

= * 2py

) O2> O

2

+

(ii) O2

< O2

< O2

+

(iii) O2

> O2

< O2

+

(iv) O2

< O2

> O2

+

2 1 . Th e electron ic configur at ion of th e outer m ost s h ell of th e most electron egative

elem ent is

(i) 2s 22p 5

(ii) 3s 23p 5

(iii) 4s 24p 5

(iv) 5s 25p 5

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2 2 . Amongst the following elements whose electronic configurations are given

below, the one h aving th e highest ionisation enth alpy is

(i) [Ne]3 s 23p 1

(ii) [Ne]3 s2

3p3

(iii) [Ne ]3s 23p 2

(iv) [Ar ]3 d 1 04s 24p 3

II. Multiple Choice Questions (Type-II)

In th e fol lowing quest ions two or more opt ions may be c orrect .

2 3 . Which of th e following ha ve ident ical bond order ?

(i) CN

(ii) NO+

(iii) O2

(iv) O2

2

2 4 . Wh ich of th e followin g atta in th e linear s tru ctu re:

(i) BeCl2

(ii) NCO+

(iii) NO2

(iv) CS2

2 5 . CO is isoelectron ic with

(i) NO+

(ii) N2

(iii) Sn Cl2

(iv) NO2

2 6 . Wh ich of th e following s pecies h ave the s am e sh ape?

(i) CO2

(ii) CCl4

(iii) O3

(iv) NO2

2 7 . Wh ich of th e followin g stat emen ts are correct ab out CO3

2?

(i) The hybr id isa t ion of cent ra l a tom is s p3 .

(ii) Its resonance structure ha s one CO single bond a nd two C=O dou ble

bonds.

(iii) The average formal cha rge on each oxygen a tom is 0.67 un its .

(iv) All CO bond lengths a re equa l.

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2 8 . Dimagnetic species are those which contain no unpaired electrons. Which

am ong th e followin g are dimagn etic?

(i) N2

(ii) N22

(iii) O2

(iv) O2

2

2 9 . Species h aving sa me bon d order are :

(i) N2

(ii) N2

(iii) F2

+

(iv) O2

3 0 . Wh ich of th e followin g stat emen ts a re not correct?

(i) NaCl being an ionic compou nd is a good cond u ctor of e lectr ic ity in th esolid st ate.

(ii) In can onical stru ctures there is a difference in th e arrangement of atoms.

(iii) Hybr id orb ita ls form s t ronger bonds than pure orb ita ls .

(iv) VSEPR Theory can explain the squ are plan ar geometry of XeF4.

III. Short Answer Type3 1 . Explain th e non linear sh ape of H

2S an d n on planar sh ape of PCl

3u sing valence

sh ell electron p air repu lsion t heory.

3 2 . Using molecular orbital theory, compare the bond energy and magnetic

cha racter of O2

+a n d O

2

species.

3 3 . Explain th e sh ape of BrF5.

3 4 . Stru ctu res of molecules of two comp oun ds are given b elow :

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(a) Which of the two compou nd s will ha ve interm olecular hydrogen bond ing

and which compound is expected to show intramolecular hydrogenbonding.

(b) The melt ing point of a compoun d depends on, am ong other th ings, theextent of hydrogen bon ding. On th is bas is explain wh ich of th e above

two comp oun ds will sh ow higher m elting point .

(c) Solu bility of compou nd s in water depend s on power to form h ydrogenbon ds with water. Wh ich of th e above comp oun ds will form h ydrogen

bon d with water eas ily and be m ore solu ble in it .

3 5 . Why does type of overlap given in the following figure not result in bond

formation?

3 6 . Explain wh y PCl5

is tr igona l bipyram idal wh ereas IF5

is s qua re pyramidal.

3 7 . In both water an d dimethyl ether (CH 3

C H3), oxygen atom is centra l

a tom, an d h as the s am e hybridisa t ion, yet th ey ha ve different bond an gles.

Which on e ha s greater bon d an gle? Give reason .

3 8 . Write Lewis s tru ctu re of th e following comp oun ds an d s how forma l char ge

on each a tom.

HNO3, NO

2, H

2SO

4

3 9 . Th e en ergy of2pz

molecular orbital is greater t ha n 2px

an d 2py

molecular

orbitals in n itrogen molecule. Write th e comp lete s equ ence of ener gy levels inth e in creas ing order of ener gy in th e molecule. Compa re th e relat ive sta bility

an d th e ma gnetic beha viou r of the following s pecies :

N2, N

2

+, N

2

, N

2

2+

4 0 . Wha t is t he effect of th e following p rocesses on t he bond order in N2

a n d O2?

(i) N2 N

2

++ e (ii) O

2 O

2

++ e

4 1 . Give rea son s for th e followin g :

(i) Cova lent bon ds a re d i rec t iona l bond s whi le ionic bonds a re non-

directional.

(ii) Water molecule has bent s tru cture whereas carbon dioxide molecule is

linear.

(iii) Ethyne molecu le is l inear .

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4 2 . Wha t is an ion ic bond ? With two su itable examp les explain th e differencebetween a n ionic and a covalent bond?

4 3 . Arrange the following bonds in order of increasing ionic character giving

reason.

NH, FH, CH an d OH

4 4 . Explain why CO3

2 ion ca n n ot be represen ted by a single Lewis s tru ctu re. How

can i t be best represented?

4 5 . Predict th e hybridisation of each carbon in th e molecu le of organic comp oun dgiven b elow. Also in dicate th e total nu mb er of sigma an d pi bon ds in th is

molecule.

4 6 . Group th e followin g as linea r an d n on-lin ear m olecules :

H2O, HOCl, BeCl

2, Cl

2O

4 7 . Elemen ts X, Y an d Z h ave 4, 5 a n d 7 valence electron s r esp ectively. (i) Writeth e molecular formu la of th e comp oun ds form ed by th ese elemen ts ind ividua lly

with hydrogen. (ii) Which of these compounds will have the highest dipolemoment?

4 8 . Draw the resonating structu re of

(i) Ozone m ole cu le

(ii) Nit ra te ion

4 9 . Predict th e sh apes of th e followin g molecu les on t he bas is of h ybridisation.

BCl3, CH

4, CO

2, NH

3

5 0 . All th e CO bon ds in car bon at e ion (CO3

2) are equ al in len gth. Explain.

5 1 . Wha t is m ean t by th e term average bond enth alpy? Why is th ere difference inbon d en th alpy of OH bond in eth an ol (C

2H

5OH) an d water?

IV. Matching Type5 2 . Match th e sp ecies in Colum n I with th e type of h ybrid orbitals in Colum n II.

Co lum n I Co lum n II

(i) S F4

(a) s p 3d2

(ii) IF5

(b) d2s p 3

(iii) NO2

+(c) s p 3d

(iv) NH4

+(d) s p 3

(e) s p

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5 3 . Match the s pecies in Colu mn I with the geometry/ sh ape in Colu mn II.

Colum n I Colum n II

(i) H3O

+(a ) Lin ea r

(ii) HC CH (b) An gu la r

(iii) ClO2

(c) Tet ra h ed r al

(iv) NH4

+(d) Trigona l b ipyramida l

(e) Pyr a m id a l

5 4 . Match th e species in Colu mn I with th e bond ord er in Colum n II.


(i) NO (a) 1 .5

(ii) CO (b) 2 .0

(iii) O2

(c) 2 .5

(iv) O2

(d ) 3 .0

5 5 . Match th e items given in Colu mn I with examp les given in Colu mn II.


(i) Hydrogen bon d (a ) C

(ii) Reson an ce (b ) LiF

(iii) Ion ic solid (c) H2

(iv) Cova len t solid (d ) HF

(e) O3

5 6 . Match th e sh ape of molecu les in Colum n I with th e type of hybridisation in

Colu m n II.


(i) Tetra h edra l (a ) s p 2

(ii) Tr igon a l (b ) s p

(iii) Lin ear (c) s p 3

V. Assert ion and Reas on Type

In th e followin g ques tions a s ta tem en t of Ass ertion (A) followed by a s ta tem ent ofReas on (R) is given. Ch oose th e correct opt ion ou t of th e ch oices given below each

question.

5 7 . As s er t ion (A) : Sodium chloride formed by the action of chlorine gas on

sodiu m m etal is a s table compou nd .

Rea s on (R) : This is because sodium and chloride ions acquire octet insodium chloride forma tion.

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(i) A an d R both are correct , and R is th e correct explan ation of A.

(ii) A an d R both are correct , bu t R is n ot the correct explan ation of A.

(iii) A is t rue but R is fa lse .

(iv) A a nd R both a r e fa lse .

5 8 . As s er t ion (A) : Th ough t he cent ral atom of both NH3

a n d H2O molecules ar e

s p 3 h ybridised, yet HNH bond an gle is greater th an th at of

HOH.

Rea s on (R) : Th is is becau se n itrogen at om h as on e lone pair an d oxygenatom h as two lone pairs .

(i) A an d R both are correct , and R is th e correct explan ation of A.




5 9 . As s er t ion (A): Among the two OH bonds in H2O molecule, the energy

required to break th e first OH bond an d th e other OH bondis th e same.

Rea s on (R) : This is b ecaus e th e electronic environm ent arou nd oxygen is

th e sa me even after breaka ge of one OH bond .

(i) A an d R both a re correct , and R is correct explanation of A.




VI. Long Answe r Type

6 0 . (i) Discus s th e significance/ applicat ions of dipole moment.

(ii) Represent diagramm atical ly the bond m oments an d the resu ltan t dipolemoment in CO

2, NF

3an d CHCl

3.

6 1 . Use the molecular orbital energy level diagram to show that N2

would be

expected to have a tr iple bon d, F2, a s ingle bond an d Ne

2, no bond .

6 2 . Briefly des cribe the valence bon d th eory of covalent bon d form ation b y takin g

an examp le of hydrogen. How can you interpret en ergy cha n ges ta king placein th e forma tion of dihydrogen ?

6 3 . Describe h ybridisation in th e cas e of PCl5

a nd S F6. Th e axial bon ds are longer

as comp ared to equa torial bonds in PCl5

whereas in SF6

both axia l bonds an dequator ia l bonds ha ve the sa me bond length. Explain.

6 4 . (i) Discu ss the concept of hybridisa t ion. Wha t a re its different types in aca rbon a tom.

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(ii) Wha t is the type of hybridisa t ion of carbon a toms ma rked with s tar .

(a)

(b)

(c)

(d)

(e)

Com prehe nsion given below is fol lowed by som e m ult iple cho ice quest ions.

Each quest ion has one correct opt ion. Choose the correct opt ion.

Molecular orb itals a re form ed by th e overlap of at omic orbitals. Two at omic orbitalscombine to form two molecular orbitals called bonding molecular orbital (BMO)

an d an ti bond ing molecular orb ital (ABMO). En ergy of an ti bond ing orbital is ra ised

above the p arent atomic orbitals th at h ave combined an d th e energy of the bon dingorbital is lowered th an th e par ent atom ic orbitals. Energies of various molecu lar

o r b i t a l s f o r e l e m e n t s h y d r o g e n t o n i t r o g e n i n c r e a s e i n t h e o r d e r :

x y z x y zs * s s * s ( p p ) p ( * p * p ) * p < < < < < <

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6 6 . Which of the following molecular orbitals has maximum number of nodal

planes?

(i) *1 s

(ii) *2p z

(iii) 2px

(iv) *2py

6 7 . Which of th e followin g pair is expected to ha ve the sa me b ond order?

(i) O2

, N2

(ii) O2

+, N

2

(iii) O2

, N

2

+

(iv) O2

, N

2

6 8 . In wh ich of th e followin g molecu les, 2pz m olecu lar orb ital is filled a fter 2pxa n d 2p

ymolecu lar orbitals?

(i) O2

(ii) Ne2

(iii) N2

(iv) F2

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ANSWERS

I. Mult ip le Ch oice Qu es t ions (T y p e-I)

1. (ii) 2 . (iii) 3. (ii) 4. (ii) 5. (ii) 6. (iv)

7. (i) 8. (iii) 9. (iii) 10. (iii) 11 . (ii) 12 . (iv)

13 . (ii) 14 . (i) 15 . (ii) 16 . (iv) 17 . (ii) 18 . (i)

19 . (iv) 20 . (ii) 21 . (i) 22 . (ii)

II. Mul t ip le Ch oice Qu es t ion s (Ty p e-II)

23. (i), (ii ) 24 . (i), (iv) 25 . (i), (ii)

26 . (iii), (iv) 27 . (iii), (iv) 28 . (i), (iv)

29 . (iii), (iv) 30 . (i), (ii)

III. S h or t An s w er Ty p e

32. (i) According to molecula r orb ita l theory e lect ronic configura t ions of

O2

+a nd O

2

sp ecies a re as follows :

O2

+: (1s )

2(* 1 s

2)

(2s )

2(* 2 s

2)(2p

z)2 (2p2

x, 2p 2

y) (* 2p

x

1 )

O2

: (1s )

2(* 1 s

2)(2s )

2(* 2 s

2)(2p

z)

2 (2p2

x, 2p2

y) (* 2p

x

2 , *2py

1)

Bond order of O2

+=

1 0 5

2

=5

2= 2.5

Bond order of O2

=

1 0 7

2

=3

2= 1.5

High er bon d order of O2

+sh ows th at i t is m ore stab le than O

2

. Both th e

species h ave unp aired e lectrons . So both a re param agnetic in na tu re .

3 4 . (a ) C om p o u n d (I) will fo rm in t r a m o le cu l a r h y d r oge n b on d b e ca u s e

NO2

and OH group a re c lose toge ther in compar ison to tha t incomp ou n d (II).

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(b) Comp oun d (II) will have higher melt ing point becau se i t forms

interm olecular hydrogen b onds. Thu s, m ore and more molecules

are joined together th rou gh hydrogen bond forma tion.

(c) Due to intra molecular h ydrogen bonding compou nd (I) will not beab le to form h ydrogen b onds with water th u s will be less soluble init while compound (II) can form hydrogen bond with water more

eas ily and will be solu ble in wa ter.

3 7 . [Hint : Dimethyl ether will have larger bond angle. There will be morerepulsion between bond pairs of CH

3groups a t tached in e the r than

between bon d pa irs of h ydrogen a toms att ach ed to oxygen in wat er. Thecarbon of CH

3in e th er is a t tached to th ree hydrogen a toms th rough

bond s an d electron pairs of th ese bond s ad d to the electronic cha rge dens ity

on carb on a tom. Hence, repu lsion between two CH3

group s will be m oretha n th at between two hydrogen a toms.]

IV. Ma t ch ing T y p e

52 . (i) (c) (ii) (a ) (iii) (e) (iv) (d)

5 3 . (i) (e) (ii) (a ) (iii) (b) (iv) (c)

5 4 . (i) (c) (ii) (d) (iii) (a ) (iv) (b)

5 5 . (i) (d) (ii) (e) (iii) (b) (iv) (a)

5 6 . (i) (c) (ii) (a ) (iii) (b)

V. Ass er t ion an d Reas on Typ e

57 . (i) 58 . (i) 59 . (iv)

65 . (i) 66 . (ii) 67 . (ii) 68 . (iii)

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