CBSE QUESTION PAPER

CHEMISTRY (Theory)
�tt,�"1 Pc.�1"1 (�oiilki&i)
CLASS-XII

. 1
Generql ·Instructions .:.
(i) All questions are compulsory.
(ii) Marks for each question are indicated against it.·
(iii) . ,Questions number 1 to 8 are very short-answer questions and
carry 1 . mark each.
(iv) Questions· number 9 to 18 are short-answer questions and carry
2 mark.s eath.
(v). Questions number 19 to 27 are also short-'answer .questions a11:d
carry 3 mark� each.
(vi) Questions number 28 to 30 are long-answer questions and carry
5 marks each.
: -(vii) Use Log Tables, if necessary. Use of calculators is not a�lowed.

fl/JIJ.q �:

fiJ . - t1fft m w¥il4 f _1

.(ii) �-JITT' if;� 3fci-� W: f I

(iiiJ · JIN-ti&:rr 1 # 8 acr; 31frr FIJ"3fflfl! m t , � · m i ffrTI: 1 _.3fi6 · t ,
--{iv) "« 18 "ffcfi ffg-3fflfl! ffl f I JffW-m iii fc;rTJ: 2 3Tc1i f I
J/N-tR§lff ·9

(v) .ffl-m§W 19·-«:27 ncfi efr "ffg-3uftir >TR f I JffW JfR it; fffil: 3-Jicn _t I .

. (vi) · m-m§lff 28 tr 30.cfW-� mi t � JIN it_fc;rr( 5 Jicf; ! 1

1.. Write a_ distinguishing feature of met�nic· ·solids. 1

� _olm � q�ilH � �-� �_f('iMQ_ I ..

2. .-Fluorine do_es not exhibit any positive oxidation state. Why.? 1

. �� q;yf �41<"�eb 3ilcHtlcfi{OI � Sl�flld � cfi«IT· I cf<IT ?
. - '

3. . Differentiate between molarity· and molality of a solution. 1

ftj('f�.-i � 'ilcl{dl am '11('k\dl -� 3TTR �- � I

2
4. Write the structure of the molecule of a compound whose IUPAC name
1S

1-phenylpropan:-2-ol 1
� • cfil �- e'{iHI fctf@Q_ f\J1�chl �-<t'TI.�.m. (IUPAC) � -� 1m
� >fc6R t
l :-rliPR1� �--i.:.2.a:i@

5. What is Tollen's reagent?' Write one usefulne�s of this -reagent. 1

� (Tollen) � · tFIT mo[_ � ? � � cf>T � 3441rlm fctf@tJ. ·1

6. ' Give the IUPAC name of the following co1!1pound : 1

H3C - / C�3
"'-- -·
H
H/-."/
/"'--Br ··
CH 3

Rkf � cfiT �.7i_1lT."Q_.#f. (IUPAC) � �- 1P1 � : .

H3C /CH3
"'-.
H
H / - "-,_ /
· /"'--Br
CH3

7'* What does the designation '6, 6' mean in the naine nylon�6; 6 ? _ 1 _
ril�t-11+6, 6 "ij '6, 6' tFIT � -cn«IT � - ?

8. What are the produ�ts of hydrolysis of sucrose ? . 1

� � �-�4�2rf -% � <FIT � ?

9. Given that the standard electrode potentials (E 0) of metals are : ·

K+ / K =· :_ 2·93 V, Ag+ / Ag = ·o-so. V, Cu2+ / Cu _ = 0·34 V,
"

Mg 2+ / Mg = - 2.'37 V, Cr 3+ / Cr = - 0·74 V, F_e2+ / Fe =· - 0�44 V.

Arrange _these metals in an increasing order of their reducing power. 2
OR

·3
 'I\vo half-reactions of an ele.ctJ:'.'ochemical cell are given below
2
Mn?� (aq) + 8 H (aq) +·5 e- � Mn + (aq) + 4 H2 O (l), E _= + 1·51 V
+

2+ 4
S.n . ·Sn
(aq) � + 2 e�,. E 0 = + 0· 15 V�
+ (aq)
. .

Construct the redox reaction equation from the two half-reactions and
·calculate the cell potential from the standard potenti�ls and _predict if
the reaction is reactant or produc� favoured. 2
� �ail it; llm �cl¾ls fcrqq_ (E0 ) �- -� � :

. K+ / K . = - 2·93 V, Ag+ J Ag - �- 0·80 V, Cu2+ / c¥ = 0·34 V, .

Mg 2+ / Mg =- 2.-37 V, - Cr 3+ / Cr = - 0·74 V, Fe2+ /'Fe = - 0·44 V.

� �ail cliT � � �qtj14{ � � � it � � <bl�((

�

�- �-{IBl�f�cfi m, �·-ey 3N-� � �-�-�:

MnO� (aq) + 8-l�� (aq) + 5 e- � Mn2+ (aq). + 4.-H 20 (l), E0 = + 1·51 V .

Sn2+ (aq) � Sn + (aq) + 2 e-, E0 = + 0·15 V.

4

B � 31lf-�3TI -� 3W:lR "CR. ©cffi (3i9i{ll19iPl) � 'cnf �'ilcfi{UI f("Jf�l(

3iR T{Rcfi fcN9T "ij m;r fcMcf qf<cfiR·m __ 3i1{ • __ fcJi � �
6ij<i!�i 3T� �. 3iffctl m1ft . I

10. Express the relation among the _ ·cell constant, the resistance of the
•
' "
•
• • • • '

solution in 'the cell and _the conductivity of the solution. How is the
co11:d�ctivity of·a solu�ion related to its molar conductivity ? 2
m, �<icti, - _m,
Mct4� c6T · "5l@U� � ftjct<H c61' illctcfidl � � � � mm
-ij_
�' � - � �. I � WfiR fckl4'1 th1 tjlz;!cfictl � lllm tjlz;!chdl "ij � _
� �?
11. · Define the t�rms, 'osmosis' and 'osmotic pressure'. What is the
advantage of using osmotic pressure as compared to other colligative
properties for the· det�rmination of molar. masses of solutes in
�olutions ? 2
'q{[*1{ot' ajtt 1RJ if � � f 3R �u]*i&1 �. cfil �
'q{ltt{oft �'·
�. 9<m{on war � a941J1 q;r r¾t-1441 �-fc@"q· ffl � � s::��H m �- � �
�WTmoJ·t?
4
12. Complete the following chemical reaction eq1,1ations : 2
{i) ·12· + HN0 3 .._;,
· (cone.)
(ii) HgC1 2 + PH3 ->

Rkffc-tfolct (IBl4Rcfi -� W-!lcff(UTI_ c6I 1l(T � : _ -

(i) · 12 + HN0 3 ->
(�)

(ii) HgC12 + PH3 �

13. What is. meant by coagulation of a colloidal solution ? Name ·any·

method by which coagillati?,n of lyophobic .sols _can be caJ'.ried out. ·2
ch1<1T�:s1 fcl<-14�· �- �--� cp;Jf � -� � ? � � fcffel. q;t .;mt�--�­
��fcrom- "ij@ c.fif-� � �-� m I
14. Describe the fo_llowing : 2
(i) Tyndall effect
(ii) Shape-selective catalysis
RJ...tfc1Rga cfiT � ch)�q_ -:
(i) �� .
(ii) •-tj(Oll(·Ji� 3�{01

15. Identify A and B in .eacli of the following processes : 2

NaCN . reduction ·
(i) CH 3 CH2 Cl --� A . . B
Ni/H2

. (ii)

ijaC� A 3i4iP-H
(i) CH3 CH·Cl
_ 2 B
Ni/H2

(ii)

5
16. Draw the structural formulae of the follo�ing compounds : · 2
"(i) H4P205
· (ii) XeF4 ·

RkifclR9a _zj)r1<lil � tj(=cH1 � a111�q: :

(i) H4P205

(ii) XeF4 ·

17. Give the chemical tests _ to distinguish between the following pairs of
.
compounds : 2
(i) Ethylamin_e and Aniline
(ii) Aniline·. and· Benzylamine ·
R9rclr@a· � � #- � � � � <1t11�8c£ � rctr@�
(i) T;MclQ!ll1 am ��k111 #
(ii) �<?11--1 � �f�(1Q�1-i �

.18. Draw the molecular structure� of the in.6rioniers of·

(i)· PVC

(ii) Teflon
. .

ch1 3iRforn· · chlM({ :

.

�-- �cbcl<lil 61lfotjcb B<iHI�

. . .

· (i) PVC
(ii) l4cll--1 .

19. Silver crystallises· in fee lattice. It the edge lerigth .of the ·unit ·cell is
4·.07 x 10-8 cm and the· density of the crystal is 10·5 g cm-3, calculate
. the atomic mass of silver. _(NA =· 6·02 x 1023 atoms inoC1 ). . . 3
ll f�R.fcld . mof �
.m. � m,
� -��� � (fee) -� I � � � �-
. �. � cbl � 4·07 X 10-S Cm miR.(1 q;f � 10·5 .g Cm-3 (11
( 23
� cfiT 9(1-tltJJ s!.c4GH 9ftcfifc;?tct cfilNll I (NA 7 .6·02 x 10 9VlltJJ "5l'fu "JTTB)

6
20. 15· g of an unknowl). molecular subst�nce was dis�olved i� 450 g _of
water. The. resulting solution freeze� at - _0·34° C. What .is the molar
mass of the substanc·e ? (Kf for water·= 1·86 _K kg mor1 ) 3
-�. � 450 g -q � -� 3ilfocfcfi � cfil. 15 g lfffi cfil � lFJT � · I � fckt4� .
·
-0·34° C � � .m<TI' � r� �
1
qiT � S:.ol!'lH "cp.fT mTTT ?.

_ .. (K� � � � = 1:s� K leg mo1- )·

21. Des.cribe the role of the ·following : .3
(i) NaCN 'in ·the extraction .of silver fr.om a silver ore-
. (ii) ·Iodine in the reµning of titan1'"?
(iii) Cryolite· in the metallurgy of aluininium
OR
. _·Describe the principle involved in each of the· following processes of
· metallurgy : ·3
(i) Frot4 floatation :qiethod ·
(ii) Electrolytic refining .of metals
(iii) Zon� refining of metals
f�CifclfuJa cb1 � q;r qUH ��Q.
(i) · �- � � �- � f�'4if.fo1 � NaC.N ch1'
(ii) 21�ZRllii � 9R'4i{Ot
. .
# 3i14lsl1 cb1 .

(iii) · Q(jMR�� � • � �14lctl��- cb1

.
31?.lcll'
• �- H�fclf@a � � -q Br¾ffia .-fo.;,s:1� q;r cfUR · � ·:
Ci) � � M�r
cu) �an. q;r �-3i9l:12�1 - qfltq:;{01
(iii) �an qi{.�- 4Rfih{OI
22. How would rou account -for the following : 3
(i) �he elec_tron gain enthalpy with nega�ive sign is. le_s� for. oxygen
than that. for sulphur.
(ii) P�osphorus shows greater tendency for. caten�ti�il than ni_trogen:
.. . .

(iii)· Fluorine never·. acts as. the · cen.tral . atom in · polyatomic

int�rhalogen compounds.

7
 Rl-.ifctforn �. q)RUT � BG$!�- :
(i) �cl�l-i mfta° cfil ;f!Ull_�qi � ��1 dilcfl-11\lH � � � cit·. cflll .
tI
(ii) ·11�?1-il-i cfil � ll11�(B •. chl 'Wffer. 31m ��-I
(iii) ai�q(q(Uj<b -�d{l�ctl13!1 if mr,� �anwr- � 'lft � 1WilUJ ch1 � if
�mmt ,-
23. How would you convert the following-· : 3
(i) Phenol to benzoquinone
(ii) Propanorie to 2�methylp,ropan-2-ol
. . . .

(iii) · _ Propene to propan-2-ol

· ·f.iklfctf@a·qif � � �:
(i) � q;f. al�f¼ct-{l-1 -ij
(ii) . S{)tf-111 q;J 2-����+2-� if
(iii) mtiR cfiT >lm"-2-afRi -ij .
24. · How· would. you -differen_tiate between SNl and SN2 mechamsms. of
substitution reactions ? Give one example of each. 3.
�- �an. ch1 sN1 am sN2·� t� 3Titf � at=n: � ? ·
� 3fcfiR cfiT �-� 3<!,l�{OI -� I

25. Write the name, the-state of hybridizatio�, the s�ape and the magnetic
behaviour of the follovying complexes
[CoC1 ]2-, [Ni(CN) ]2-, - [Cr(H 0)iC 0 )
4 4 2 2 42 r
(At. No. : Co = 27, Ni -·=. 28, Cr = 24) _ 3
.
f.tl-.ifctf@a cfi'fl-i{qcRfi � -;w:r, � ffl, _. 3th: -ijRiichlll c44�R fctf@Q_ :
[C0Cl4]2 , [Ni(CN)4]2.:., [Cr(H20)2<C204)2r .
-

(� � :·Co= 27, Ni= 28, Cr= 24)

26. Differentiate between fibrous proteins and globular proteins. What is
meant by the denaturation of a protein ? ·3 ·
� -miR � · nct1ctiR miR if·� � � -, _
2 miR � fci�ct1cJi{o1
(denaturation) � antr cFlT - � ?

8
 27. _ Explain the following terms with an _ example for each : 3
(i). · Antibiotics
(ii) Antiseptics
(iii) Analgesics
R'-if�ftia � cfil" �-� dGl�{01 � � "&JR§ql �

(i) �,fct�ftjcf> � (Q}?.�l<ilR.iR-1)

(ii) � ffl (qf-=c.ijfQ.iR-1)
(iii) cfl-$m1-0 � (�cl�fflcRt)

· 28. (a). Complete the following chemical equations :

(i) C.r2of- (aq) � H S (g)-; H - (aq) � -
2
+

(ii) Cu2+ (aq) + 1- (aq) �-

(b) - How would_ you account-for the following :

<·
(i) TI?-e oxidising power of oxoa:q.ions are 1n the order
vo; Cr2o�- < MnO�.
(ii) The third ionization enthalpy 'of manganese (Z = 25) is
exceptionally high.
(iii) Cr2+·1s a stranger re·auc1ng
.- agent than Fe2+. 5
OR
(a) Complete the following chemical equations :
(i) MnO� (aq) + s20;- (aq) ·+ Ii20 (l) -4 .

(ii) Cr2O�- (aq) + Fe2+ (aq). + H+. (aqJ �

(b) Expl�in the following observations :

(i) La3+ (Z = 57) and Lu3+ (Z = 71) do not show ariy colour in
- solutions.
(ii) Among the. divalent cations in the first series of transi!ion
elements, manganese exhibits the maximum
paramagnetism.
(iii) Cu+ ion is not known in aqueous solutions. 5

-9
 (a) Rklfctftia (IBllJRcfi ijl-flcfi(OTI � � -� :
(i) �r2o;- (aq) + H2S (g) + H (aq). -4
+

(ii) Cu2+ (aq) + r· (aq} -)

Ch) RklfclroJ.a cfiT cnRUT fct@qi( � � :
(i) �lfflSfiOllllrTI ·cfil ¢ilcf«lqi(UI � vo; < Cr2o;-·< MnO� ��
if mfil t I
. (ii) �·11;il� (Z = 25) � � m � 3H. � "ITTill � I
. (iii) . Cr2+ � Fe 2+ � � � -:SlqiJlllcfi. � I
mrsrr
(a) Rklfctftia (lflP-IRcfi·. e'ilcfi(ofi � � i:blNiQ. :
(i) MnO�. (aq) + Sl)i-. (aq) + -H20 (l) .-)
Cr2o;- (aq) + _Fe (aq) + H (aq) -�
2+ +
(ii)

(b) Rklfctftia -6lctct\i:ii-TI cbl <:i?H&u -� :

(i) La3+ (Z = 57) ·am Lu3+ (Z = 71) fclctll-TI � � "t1T � fG@cild I
(ii) � wrft � tj��UI . mcTT � fati�¾ �Hl4.fl -q �·11.fl)l\ � .
6lfl'4ch� Q��,a·· cfi«n � I
(iii) � fcfftll�l # Cu+ � q;r 3-!R-<1¢:t · ;r� �.. � I

29. (a) Explain the following terms :

(i) · 'Rate of a reaction
(ii) Activation energy of a reaction
(b) The decomposition of phosphine, PH 3, · proceeds accor�ing_ to the
following equatio'n :
4 PH3 (g)-) P4 (g) + 6 H2 (g)
It is found that the reaction follows the following rate equation
Rate = k [PH3].
The half-life of PH3 is 37·9 s at 120 ° C.
(i) How much time is required for 3/lh of PH3 to decompose ?
.
(ii) What. f�action of the original sample of PH3 remains behind
after 1 minute ? 5
OR
10
 (a) Explain the following terms :
. (i) Order of a reaction
(ii) · . Molecularity of a reaction
(b) The rate of a reaction increases four times when the temperature
changes from 300 K to 320 K. Calculate the energy of actiyation
of · the reaction·, assuming that · it does. not change. · with
1
temperature: (R = 8·314 J K� . inor� )
1
5
(a) Rctfclfokl 1:re) �. � � ·:
� cfil � .
.

(i) .
(ii) � cfil €rai4UI � .
( b) 'h,l,fl-hl-i' PH3, cfiT 319€12� 8i.-ifclf(9n €lilcfi(Oi � -� mm' � . :
4 PH3 (g) � P4 (g) + 6,-H2 .(g)
� wn \l{@T � fen -� Rk-i@furn � B'i1cfi(OI � � mm � :
� ::;: k [PH3].
· 120° C 1R PH3 cfil. 3l'tr-� 37·9·s I t
(i). PH3 � 3/4 'llf1T � 3i9�R:a m���� ffl ?
(ii) 1 n:RZ - � 4�-clk( PH3 � � Slfoe.�f cfiT � � ffl" W � ?
-31�
(a) . ��� m <l,}f¼Q_ :
en �--��w
(ii) �� tt �lfoclcfi<ll
(b) i:114.4H 300 K � -� 320 Km � 1R_- "Q_cll � ch1 -� � :fIT "ITT �
� I � cfil. Hf��o1 -� q,"T qitbf!H �' � ff'. � fcfi dl9iiH
1 1
� � Wf � llFf qfo:1ffia � � �- I (R = 8�314 J K- mor )
. .
30. (a) · Illustrate the foliowing natlle 're�ctions giving a chemical ·equation
. in each case :
(i) Clemmensen reaction
(ii) Cann.1zzaro's reaction
(b) Describe how the following conversions can be brought abo:ut :
. .

(i) Cyclohexanol to cyclohexan-1-one

(ii) Ethylbenzene to benzoic
' �
acid .

(iii) Bromobertzene to benzoic acid 5

OR

11
(a). Ilh,1.strate the following ria�e reactions :
(i) · Hell - Volhard --- Zelinsky
.
_reaction
(ii) . . Wolff� Kishrier redµction reaction
(b) How _are the fol19wing. conversiop.s carried out :
(i) . Ethylcyanide to ethanoic acid
. (ii) Butan-1-ol to butanoic acid · ·
(iii) Methylbenzene to benzoic acid
Write chemical equations for the involved reactions; 5
(a} . Hi.:tfctforn � cfTffi'- �3lf ·q;) � · � · � <lfll�Rcfi H�tcfi(OI tli<
fctfut.Q. :
(i) #llGrlFl. �
(ii) . %R�iil <€t- � ·
(h) q1JFf' � � R9fctfurn �qia<o, �. �- � � : .
(i)- BW-@1�&4..ffct cnT fll�ck11�cf8+ l-3Wl rt
(ii) 1lf¼cl��'1 q)f ��$qi � :q .
(iii) �1Jfi4.:/4l11 � ��l�&i � rt
31�-

(a) RYfctf�a � cfil �an

cfil_ 3�1Q(OI � m f�f{9Q_ :
Ci) -%B- cn�1J --. �fa{4) �
(ii) � - � dl4iP-H �
(b) �- �Yict(OI � � � -� � :
(i) �fl4Z.HWFil�:S tlif ��-�-if
(ii) . �-1-3lffi � �l-il�cfi � ir
. · (iii) -qf�cl��1'1 cnT ��l�cfi � ir -

12