~OLUTION~J - askIITians

406 AffMS EXPLORER

~OLUTION~J

I PHYSICS .1. (c) : The motion of the water boat disturbs thesurface of water. Bow waves are generated on the surface.These are transverse waves at the surface. Inside thewater, the vibrations of the rudder produces longitudinalwaves.2. (d): In orbital motion, the angular momentumvector is perpendicu lar to the plane in which the rotationalmotion take place and its sense is given by the righthand fist rule. When the fingers of right hand fist pointin the direction of motion, the thumb is in the directionof [ (angular momentum).3. (c): AX -7 A-·Y+a·

(parent nucleus) (daughter nucleus)As the parent nucleus is at rest, then according toconservation of momentum.=> 0 = lII)'l'r + lIIaVa

=> O;=(A-4)v)'+4v

=> I')' ;= ~ , the recoil speed of daughter nucleus.

4. (b) : Antiparticles of stable particles (such as theposition and the antiproton) are themselves stable.However, when a particle and its antiparticle meet, theannihilntiori reaction can occur, the particle andantiparticle both vanish and instead two or more photonscan be produced. Conservation of energy and momentumrequire that, neglecting the kinetic energies of the particles,when two photons are emitted each must have an energyequal to the rest mass energy of the particles.Thus when electron-positron pair annihilate each other,the energy released is equal to rest mass of electronand positron.

e: + e+ -7 Yl + Y~[/~1 == E'(2 "" 0.511 MeV ==0.8 x 10-1.1 J]

~~~~t.~_~.!.~::.Preleased ;= 1.6 x 10-13 J.

5. (:1) : Stoke's law: 6;rrllv==i1tr'(p-cr)g

As Ai is given, p=-.M....~TCrJ3

But as r) increases, AI also increases and p is a constant.a also is a constant.•• V, the terminal velocity ex r2.

6. (b) : The spring constant of spring connected inseries is equal to

k = klk2 kkl + k2 2

Thus frequency of oscillation of given system isIrk

/== 2it~2m' .

7. (a) : When stopping potential is applied no electronwill reach the cathode and the current will becomes zero.

1 ,. . eVa ==2I1n"I~lnx

Al I 2 J k J' .so, '2I11Vma.x = IU - worx unction;= 4 cV - 2eV = 2 eV.

=> eVo = 2 eV => stopping potential ==2 V.8. (a) : While describing circular path, the centripetaland centrifugal forces are balancing each other.

1IIIV-=> --=q~'B

r(as the uniform magnetic field is acting normal to theplane)

I'==~ ...... I'p flIpV 2eB 2mp_qB --- -=-x-=-- [asm=4111]'a eB Ina V 4mp a "

I' , : "« ;= I : 2.

9. (c):. Two parallel beams of positrons travellingin the same direction is the same as two parallel currentstravelling in the same direction.They attract each other.10. (b) : The magnitude of theelectric field at a point exterior

to the sphere is -4 I ~.1tEor:

The magnitude of electric fieldinside the sphere is given by

I Qr4itEo;;r .Th..':_~eld is directly proportional to r.

r

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Solutions - 2004

.....

407

II. (a): Any surface which has same electrostaticpotential at every point is called an equipotential surface.Electric field is always perpendicular to an equipotentialsurface. Therefore x-direction is perpendicular only toy= plane.

12. (b): According to Stefan's law, the radiation energyemitted per second per unit area ofa black body = (JT~,

where (J is called Stefan's constant.Energy emitted oc;/'['I ~ E cc 4ru.l1'4where A = area of the body, T = temperature in Kelvin.When sun expands such that its radius becomes 100times its present radius and its surface temperaturebecomes half. Then energy emitted by it is

E cc 411:(100)2,.2 (~fa::C~ot E

Total energy emitted will be increased by

£' (100/4)2 EIi. . E = 625.

13. (b): The variation of specific resistance withtemperature is given by

P = Po [I + a( T - 1'o)Jwhere a '" temperature coefficient of resistance whichis negative for semiconductor.

p = Po - poa (1' - 7'0)Comaring with straight line equation, y :::fIIX + C

.~ 111, slope is negative.

14. (c): Accordingto

a,l 1[1,~------,---~----

~narrow arteries

continuity theorem as(IV = constant

as area increases velocitydecreases. So whenblood flows from narrow arteries to wider one, velocitydecreases. According to Bernoulli's principle,

I ?P+-pv- '" constant2As velocity decreases, pressure increases. Thus whenarteries become narrow, blood pressure increases.

15. (d): According to thefight hand rule wrap the righthand around the axis of rotationso that the fingers are pointingin the direction of rotation. Thethumb points in the directionof angular velocity.

twangularvelocity_-t-t"__._

axis of'rotation

16. (d): Magnetic field at a point on the axis of aloop is given by

B = .!:!L 27(1R241t (R2 +,,2 )3/2

When r> > R,

B",~IO 21tR2j ",1.10 Ai41t 1'3 21t ,,3' Thus, B oc (1/1'3).

17. (a) : Sodium lamp light emits monochromatic lighti.e. it is comprised of only one wavelength (deep yellow).This colour is scattered less in the foggy condition whileother light sources produce light at many different discretewavelengths and all provide some degree of colourrendering. Also sodium lamps emit light very near tothe peak sensitivity of the human eye under normalviewing conditions.

18. (a): Magnetic field at apo int outside the straight Btconductor is

B=~21t1"

i.e. B oc (III') (" > a).Magnetic field at a point lying inside the conductor is

B cc r (r < a).

19. (b) : In the other graphs, at a particular time morethan one velocity is shown which is not possible in realisticsituation .

20. (d): Velocity of second piece can be find out usingconservation of momentum.

0= mil'l + m2v2 ::;; 2 x "1 + I x 80~ VI = --40 m/s.Negative sign showing that particle is moving in oppositedirection of other particle direction.Energy imparted to the fragments are converted intotheir kinetic energy.

I ~ I 1. . Total energy = 2mlvl~+ 211121'2-

I 1= Zx2xI600+ZxlxMOO

= 4800 J = 4.8 kJ.------------------21. (c): The presence of thin mica in the path of oneof the interfering beams changes only the path differencebetween the beams due to which the pattern shiftsupwards. But the fringe width remains the same. Asmochromatic light is used, one cannot make out whichis the central shift as all the fringes are having the samecolour and intensity.


408

22. (d) : If the refractive index of two media are same,the surface of separation does not produce refractionor reflection which helps in visibility.__:_----

23. (c): Human ear can hear frequencies upto20,000 Hz. So for closed pipe,

I1Vovertone, U "" 4L "" n x fundamental frequency20,000= n x 1500 =. n= 13.

Maximum possible harmonics obtained= 1,3,5,7,9, 11,13 ;.

Therefore one can hear maximum upto 13,h harmonics.Overtone = 7 -. I = 6.

.~~--------~~~~---24. (a) : MRI is extension ofNMR or nuclear magneticresonance imagning. Magnetic resonance imaging is anoninvasive technique which uses strong magnetic fieldfor generating resonance at low radio frequency in theprotons present in the body.

25. (b): Using carbon dating, samples of wood,charcoal, bones, and shells have been identified as havinglived 1000 to 25000 years ago.

-.---.-----

26. (b): The energy stored in capacitor = ~CV2

= ~x40xlO-(,x(3000)2

=20 x 9x 106x 10-6= 180).The power delivered in 2 ms is

'" ~=90xI03 W = 90 kW.2 x 10-3

27. (n): In each row all the 5000 electroplaques areconnected in series.Therefore, equivalent emf"" 0.15 x 5000 <= 750 V.Equivalent resistance = 0.25 x 5000 "" 1250 Q.

All 100 rows are connected in parallel.Therefore voltage = 750 Y.

Equivalent resistance = 112g~= 12.50 Q.

Thus resultant ci rcuit of eel becomes

I "1(:5500 n

If 750Current across 500 Q == R - 500+ 12.50 1.46 A

I"" 1.5 A.

28. (b): At /I, temperature = To, volume == Vo,pressure - Po for n moles ofmonoatomic·gas.At A. l'oVn = IIR7~ (cold)

AIIMS EXPLORER----.--.---- ..-.-,.------...--~--

At B, 2PoV(j = nRT'hi~h ~ T = 2T'oMaximum thermal efficiency of the reversible engineof this Camet's cycle

Tc . To Izs: 11'" 1- ~ zzz 1- r =? == 50%.0, -1'0-

29. (b): Molecular bonding of O2 based on orbitalsshow that O2 is paramagnetic, which is trueexperimentally.

30. (c): This is made of optical fibres whose interioris coated with a refractive index greater than that of theouter cover, glass.31. (b): In electron microscope, electrons arc usedas the 'light source'. The resolving power of a microscopeis approximately equal to that of wavelength of the lightused. The de Broglie wavelength A of a particle is relatedto its momentum p by

A=!!..==A{J IIIV

The speed of required electron is

v=A= 6.63xI0-34 Is 7.28x107 m/s

m'A. 9.llxl0-Jlkg.IO-llm

1·) . d ki fEr 2lIS correspon s to metic energy 0 ~ =="21111'

=.!.x9,llxI0-3Ix(7.28xI07ix leV2 1.6xlO-11J J

= 15.1 keV,

32. (b): In compact disc colour results due tophenomenon of diffraction, in which small ripples on"the surface of it break up white light into the colour ofrainbow.33. (d): The electrostatic force due to one Cs ion isbalanced by diagonally opposite other Cs". Thus thenet electrostatic force on CI' ion due to eight Cs" ionsis zero,

34. (n): The graph showing that greater the bindingenergy per nucleon, the more stable the nucleus is. Thegraph has its maximum of 8.8 Me V/nuclcon when thenumber of nucleons is 56. The nucleus that has 56 protonsand neutron is ~~Fe, an iron isotope. This is the moststable nucleus of them all, since maximum energy isnceded to pull a nucleon away from it.35. (d): The magnetic moment of a current carrying'conductor is i . 1111: ,.2 == iliA.i.e. Magnetic mornent « ]"2.

----~-------------------36. (II): Cyclotron frequency


: .Sotulions - 2004

- qBU=--

Ztun 2x3.14x9.1xlO-31

'" 28 x 109 Hz "" 28 GHz.-.-~----------~---- -_-------37. (c): Truth table

.:I B A' 13' ro 0 I 0o 0 0

o 0 I 0o 0

A~1'r

8 -B' ..

911tpu~_of t~~s is ~al11eas that of AND gate.38. (a): When Ge specimen is doped with AI, thenconcentration of acceptor atoms is also calledconcentration of holes.Using formula, 11/ "" 170 Po. wheren, = concentration of electron-hole pair == I019/m3

110 = concentration of electronPo = concentration of holes == 10"1 atom/nr'= ._..~_L~'~l'"_~.9~~I/o ~ no == 1017

/1113._. _

J3K T JK T39. (b): "0111 == -_/1- == 1.73 _11_- III III

V _ == lK liT:: 1.60JKIlT,II tun m

- J2K/IT -\ 41JKIIT1 '}III' --- --;;;- -. --;;;-

~~:_om_.~!l_esec'lu~tio~~! Vrnl,.> 1'",. >__1_::'''::L:1''_' __ • _

40. (b): Force of attraction between two charges isgiven by

F =_1_ (iI(h4m::O ,.2

_ I I (NI2 A 2'1'2Co _ 4rr 'F?== MLr2L2

(where 4n is dimensionless)== M--! L-.1T4 A2.

------------------41. (d) : The electrical force of a cell or battery calledelectromotive force (emf). This force, which makeselectrons flow around a circuit. Each kind of cell hasa particular emf. The size of a cell has no effect on itsemf. The chemicals in the cell determines its emf, butlarge cells last longer than small cells of same basictype. This means that from a large cell, we get a particular:I~~!~E~:._~~..!:.~tim~_ as compared to small cell.42. (b): A red object reflects red colour from a lightfalling on it. Thus when this object is viewed in yellowlight then it absorbs all yellow light falling on it and

_appears dark. From Rayleigh's scattering is inversely

409---- -----------

proportional to )..-1. Red colour has largest wavelength;therefore this colour is scattered least as compared toother colours. --------.----------43. (c): The pressure cooker works on the principlethat boiling point of a liquid increases with increase ofvapour pressure above the liquid. Water, along with foodto be cooked are heated in a closed vessel, so that theconfined water vapour raises the superincumbent pressure.As a result, water boils at a temperature higher than100°C. When the cooker is removed from the stove andthe lid is removed, pressure again decreases due to whichits boiling point decreases and water starts boiling again.44. (<I): From thecompass we arc ableto know the directionof the magnetic poles.The north of compasspoints towards themagnetic south pole.If we know themagnetic declinationat that particular place(which is anglebetween geographic meridian and. magnetic meridian)we can easily find out the true geographic north-southdirection.Imaginary lines drawn along the earth's surface in thedirection of tile horizontal component of the magneticfield of the earth at all points passing through the northand south magnetic poles. This is similar to the longitudesof the earth, which pass through the geographic northand south poles. ----~---45. (a): Normally when a body is moving in a straightline, whatever be the internal changes, the centre of masscontinuous in its trajectory with the same velocity anda system that is rotating continues to rotate with thesame angular velocity and changes occur in such a waythat the angular momentum is conserved. Classicalphysics, taking the whole of the earth as a system doesnot allow sporadic changes in the speed of the earth.However, according to the information on the earth'srotation. by U.S. Naval observatory sporadic changesof the speed of rotation of the earth have been observedand this is attributed to the influence of the moon onthe tides. This makes it necessary to take the earth andthe moon (at least) as one system.In the reason given, though normally when taking the


410 AIfMS EXPLORER

earth as a single system, internal changes do not affectthe motion, now that one has to take the earth-moonsystem, the reason that the earth's angular velocity canalso change due to the events on earth alone cannot beruled out. Then the total angular momentum of the earth-moon system will be conserved. The reason is also right,though according to the rules of the game for the 12thclass exami nations, one can take only the earth as a wholeas a system. In that case, both the assertion and reasonare wrong.

46. (c): The base is lightly doped and very thin, thisconstructional feature is key of transistor action due towhich only few holes (less than 5%) are able to combinewith the electron in base region. Most of the holes comingform the emitter are able to diffuse through the baseregion to the collector region.

47. (a): Assertion is true.· j~Sr decays to jg Y bythe emission of ~-rays. Sr gets absorbed in bones alongwith calcium.Reason is also true. 90Sr ~ 90y

Strontium decays to Yitrium. This emits ~-rays of veryhigh energy. Sr does not emit y-rays. The damage is bythe I)-rays only.

48. (c): Many Morpho butterflies are coloured inmetallic, shimmering shades of blue and green. Thesecolours are not due to pigmentation but due to iridescence:the extremely fine lamellated scales covering the Morpho'swings reflect incident light repeatedly at successive layersleading to interference effect that depends on both thewavelengths and angle of incidence. Thus the coloursproduced vary with viewing angle. However they areactually surprisingly' uniform, perhaps due to thetetrahedral (d iamond-Iike) structural arrangement of scalesor diffraction from overlying cell layers. This structuremay be called photonic crystal.

49. (a): For the human eye, the resolving power orangular separation of objects changes as distance fromthe object changes. Thus when we are close to the paintingour eyes can pick out the separate colours of dots. Butwhen we move away from the painting, our eyes blendthe dots and we see differcnt colours.50. (a): Since superconductors exist only below acertain critical temperature and above that temperaturethey behave like normal materials. When magnet is placedabove superconductor and cooled using liquid nitrogen.

The induced magnetic field inside the superconductor .is exactly equal and opposite-in direction to the appl ied •magnetic field, so that they cancel within the superconductor. These poles will repel each other and the ..force of repulsion is enough to float the magnet.51. (a}: When a heavy nucleus splits into two medium- •sized ones, each ofthc new nuclei will have more binding :energy per nucleon than the original nucleus. The extraenergy will be given off. e.g. if the uranium nucleus

2~iU is broken into two small nuclei, the binding energydifference per nucleon is about 0.8 MeV.The total energygiven off is therefore

0.8 MeV x 235 nucleon = 188 MeVnucleon

52. (c): The excess pressure inside the small drop islarge as compared to the large drop because of whichsmaller drop of liquid resists deforming force better thanthe large. drop.

27'Excess pressure= rwhere T '" surface tension

r '" radius of liquid drop.Therefore excess pressure is inversely proportional

to itsradius and hence the surface a._rc_a_.__

t ~) water .<;-v~ c:;.:J ?(> ,p'"..., ",,,,Ii53. (b) : ."oi3.. icc steam

temperature _____.

It can be easily seen from the graph that as pressureincreases the melting point of ice decrcasc.s_.~ __54. (a) : A bombarding particle gives up most energywhen it makes an clastic collision with a particle ofsimilar mass. For neutrons, hydrogen atoms would bemost effective but unfortunately absorption occurs.However, deuterium (heavy water) and carbon (asgraphite) are both suitable in which less absorption occurs.Therefore they are used as moderators,

55. (c): If one takes two frames with origin eJI andO2 and if a body P is at rest, both according to 01 aswell as 02. The body is at rest. If the frame is movingwith a constant velocity, the same observation will notbe made. Therefore a frame moving with a constantvelocity cannot be taken as an inertial frame. Assertion


Solutions - 2004

is right.But the reason given is wrong because the frame onwhich Newton's laws of motion are applicable is aninertial frame.56. (b): Helium-neon laser uses a gaseous mixture·of helium and neon. An electric discharge in the gaspumps the helium atoms to higher energy level, (whichis meta stable energy level).

2(}.61 evcollisinn

~ }O.6(,c,;V

metastable -f'V\f1J\.r7 632.8 11Ill

'I.N\IIr'"> laserI ~.7() cV transition

spontaneous-r ;i;~;i;t;(emissionLnlCSS transition

NI! groundSlate

ground--L.._state lie

Sequence of transitions in I-Ie-Ne laser.Then these helium atom excite the neon atoms to higherlevel by collision and produce an inverted populationof neon atom which emit radiation when they arestimulated to fall to lower level.

57. (b): Input impedance of common emitter

6V/I/:' Iconfiguration = 6i'l r

J o:= constant

where 6VIII, == voltage across base and emitter,6i/l = base current which is order of few

microampere..~_._~~.:P.~~ impedance ~f_common emitter is low.58. (a) : In an irreversible process, there always occurssome loss of energy, This is because energy spent in

•working against the dissipative force is notrecovered back. Some irreversible processes occur innature such as friction where extra work is needed tocancel the effect of friction. Salt dissolves in water buta salt does not separate by itself into pure salt and purewater.59. (c): For diffraction, the slit width should be ofthe order ofthc incident wavelength. The regular spacingof the atoms in crystal is ofthe order of wavelength ofX-rays (0.1 run) because of which X-rays are diffractedfrom the crystals ...-~.-.-.-.--..------.----------------60. (d): Photoelectric effect can be explained 011 the

411---------------------

basis of quantum theory or particle nature of light wherewave nature of light fails to explain the photoelectriceffect. The number of photoelectrons is proportional tothe intensity of incident light.I'" nlro where n is the number of photons emitted/absorbedper unit area per second. nand hu are independentfactors.

~ CHEMISTR~ j'61. (c): B(Ol-lh in aqueous medium coordinates amolecule of water to form the hydrated species

1-1)0 -t B(OHh. In this species, BJ~ ion, because ofIIits small size, exercises a high polarizing power therebypulling the sigma electron charge of the coordinated 0atom towards itself. The coordinated oxygen, in turn,pulls the sigma electron charge of the OH bond of theattached H20 molecule towards itself. This facilitatesthe removal of H" ion from the 0 - H bond, as shownbelow.

II" ./0 -t B(OH») ~ [B(OH)4r + H ~

I-IThus the solution of 8(01-1)) in water acts as a weakacid. That is why it reacts with NaOH solution to producethe sodium salt.

B(OHh + NaOH Na +[B(OI-1)4rNa+B02- +21-1psodium

metaborate

62. (b): The total number of points of attachment tothe central element is termed the coordination numberand this can vary from 2 to as many as 16, but is usually6. There is no way to predict the coordination number,The arrangement of coordination number 2 is not verycommon for first row transition metal ion complexes.Some of the best known examples for silver (I).For instance, a method often employed for the detectionof chloride ions involves the formation of the lineardiamminesilver(J) complex.The first step is :

Ag" + CI- -t AgCI (white ppt.)and to ensure that the precipitate is really the chloridesalt, two further tests must be done:

AgCI + 2NH) 4 [Ag(NI-IJbl'·and [Ag(NH))2]+ + HNO; -) Agel (ppts.)Tile reaction of a bidentate Ilg,lIll: such as .


412 AIIMS EXPLORER

Nonlinear and nonplanarO,1',l1Iolecule structure of l l.O, molecule.

In O~F~, one 0 - 0 bond and two 0 - F bonds arc lyingin different planes, i. e. this molecule like 1-1202 has non-linear and non-planar structure.----- .__._---_ ..

71. (a): Gallium is a chemical clement in the periodictable that has the symbol Ga and atomic number 31. Arare, soft silvery metallic poor metal, gallium is brittleat low temperature but is liquid above room temperatureand can indeed melt in the hand.

MI. (c): Acidified KMnO.1 is decolourised by H20Z Gallium metal expandsby3.1 percent when it sol 'ifies,in following way. and therefore should not be stored in either glass or2Ki'vInOI.;. 3l-12SO.1 -) K:S01 + 2tv11lSO.1+ 3 H~O + 50 metal containers. Gallium also corrodes most other metals

?l1~():_~_~0-} ~_~~_:_f"_~~~_. ..__. . by diffusing into their metal lattice.2K1\II10I -l- ~I-I,SOI + 51'100.2 ~ K,SO.1 + 2MnSO,' .....~--- ..-..---.-~.---.-, -"--.~.---,,---.

- - - + 81-1,0. + 50., 1 72. (c): According t~ solubility rule following- - compounds arc soluble III water:

1,2-dinminocthanc with Ag" does not lead to chelatedring systems. but instead to linear two coordinatecomplexes. One reason for this is that bidentate ligandscan not exist in trans arrangements that is they cannotspan !80 degrees.

II,N.......... /CI(a) : Pt, is not an organometallic

],1N/ '-CIJ

compound as it does not contain carbon-metal bond.Cisplatin is an inorganic compound, used as anticancer~I~_l~gan~fall~~~~.class of DNA damaging agents.64. (d) : Nickcl(lI) forms a precipitate with the organiccom pound d imethylglyoxi me, C4H6(No.l-I}z. Theformation of the red chelate occurs quantitatively in asolution in which the pH is buffered in the range of 5to 9. The chelation reaction that occurs is illustrated

63.

below.H)C\ FI,

/7-~c;>_N N-c;>H Ni Hb-N N-b

\\ 1/C-CI \

!I,C CH,Ni([)z\IG)1

t\ lthough the loss of one proton occurs from one oximegroup (No.H) on each of the two molecules ofdimethylglyoxime, the chelation reaction occurs due todonation of the electron pairs on the four nitrogen atoms,not by electrons on the oxygen atoms. The reaction isperformed in a solution buffered by either an ammoniaor citrate buffer to prevent the pH of the solution fromfalling below 5. If the pH does become too low theequilibrium of the above reaction favors the formationofnickcl(!1) ion. causing the dissolution ofNi(DMGhba~~ ~~.t~~e mo'!'!~~_.!_i_guor., ~~~ __

(a) : Stabi Iity of oxides of higher oxidation statesdecreases with increasing atomic number.Nitrogen exhibits a large number of oxidation states suchas ,',1. ,',2. 'd_ ';-4. +5 in Nzo.. NO, N20" N20., and N2o.S'

... ,,',- ,.. "'_-' ....,,-.- ..~-.~

+ 2!1'

Thus, for 2 moles of KMnO., required H2o.2 = 5For 1 mole of KMnO., required H2o.2 = 5/2 mole.67. (c): Azide ion is a linear molecule, it is a pseudohalide and formal oxidation state of N in azide ionis -I.

2- ~. .;- .,-N,-::N-N=N: ~ :N= N-N: -E 7 :N=N=N:

. •• + + •• major

68. (a): Optical isomerism is very common inoctahedral complexes of general formulae.[Ma2b2cJ"±, [Mabcdef], [M(AA))]"\ [M(AAha2]"\[M(AA)a2b2]"\ [M(AAhab]"± and [M(AB)J}"=,where AA is symmetrical bidentate ligand and AB isunsymmetrical bidentate ligand.Octahedral complex ofthe type Mn4b2 and Majb, exhibitgeometrical isomerism.69. (d): F CI BrElectron affinity -3.6 -3.8 -3.5 -3.2The low value of electron affinity of fluorine is probablydue to small size of fluorine atom, i.e. electron densityis high which hinders the nddition of an extra electron.-----------70. (b): o.2F2 and H2o.2, both have open book type.structure.


Solutions - 2004 413

(i) All common group IA and NH/ compounds.(ii) All COmmon NO] - (nitrate), CH)COO- (acetate),CI04" (perchlorate) compounds

. (iii) All common CI-, Br=, 1-compounds, except thoseof Ag', Pb?", Cu" and Hg2

2+ (mercurous)(iv) All common SO.\2- (sulphate) compounds, exceptthose of Ca2-l', Sr2+, Ba2+ and Pbz+.

73. (a): The vapours of trialkyl borates B(ORh orR)BO] burn with green edged flame. This is the qualitativetest of borates.

280.1- - - + 3H2S04 ~ 3S0/- + 2H)BO)boric acid

H.1BO) + 3ROH ~ R)BO) + 3H2074. (d) : The nitrate ion has three resonance structure,with the double bond on a different oxygen for each.In all resonance structures the nitrogen has three bonds,therefore, its hybridisation is Sp2. Each of the oxygenatoms also has Sp2 hybridisation, since the hybridisationis determined by the resonance structure with the doublebond, where the oxygen has a double bond and twolone pairs.The actual geometry of the polyatomic ion is trigonalplanar with bond angles of 120°.

"0--1:,\ 1200

.1>1 ). /"'-0''g .,

NOz- : 18 electrons; ideal geometry trigonal planar,Sp2 with bond angle of 116°. .

N=O'/ .':0:..~.

•• R.N-O:~ ..

-,Q.

N02 : 17 electrons, ideal geometry trigonal planar; Sp2

with bond angle of 134°.

(j)N= O'/ .'

:0:..~(j). .-~'

N-O:~ ..-,Q.

NOt: 16 electrons; ideal geometry linear; sp withbond angle of 180°.

O=N=O.. (j)._--_._---------------

,t- -

75. (d): CIIJNH;CI is a salt which can be completelyionized in aqueous solution.76. (c): The basicity is a measure of a compound's

.'_

ability to accept a proton (Hi'). (b) and (d) arc weakerbases as the lone pair are involved in resonance. In (a)carbon adjacent to N is SIP hybridised hence is moreelectronegative therefore, pulls the electron density fromnitrogen.

77. (a, d) : A I° hydrogen atom is one that is bondedto a 10 carbon atom; a 2° hydrogen atom is one that isconnected to a 2°. carbon atom; etc.

1°H)C,3° 1°H C/C = CI'!2 (only I ° hydrogen atoms)

J 10

feH ~H vinylic carbon10 I J I ) .loj

H)C- HC -·C =CH2:3° .

ryu

Ci-I,?o/ '\ 2"

H~C CH,-I 12' -

H,C20 CI12- "2"/. CI-I

2

(2° hydrogen atoms)(1° and 3° H-atoms)

acctyJinic carbon1°CHjC == CH.' (only 1° hydrogen atoms)

78. (a): (a) V; 411+ 2 = 2. 11= (I (integer)+

(b) 0; 411+ 2 =4. 11=0.5+

(c) 0;411+2=4,11=0.5

(d) V ;411+2=4,11=0.5

Only (a) obeys Huckel's rule ..79. (c): The value of dipole moment of acetophenoneis 3 debye, which is maximum among the givencompounds.80. (d): In all other compounds the groups presenton doubly bonded carbons are identical.81. (a): Acetophenone does not give addition reactionwith NaHSO) .

82. (d): In alkyl halides, polarity of C - Br bondincreases with increase in chain length.83. (c) 84. (c)85. (c): - CH) group is 0- and p- directing group •however - COOH group is meta directing, thus the newentering electrophile occupies the position which shouldbe 1/1- with respect to - COOH group and P: with respectto - CH) group .


414

86. (a)

87. (c): Melting points are normally higher for primary~~~lides due to presence of hydrogen bonding.

,:::__-

88. (d) : Pyridine chloro chromate (PCC)[CsHsNH'CICrO)-] selectively oxidizes primary alcoholsto aldehydes. Secondary alcohols can be oxidized toketones with PCe.

~?~)_--------------,90. (b):n=4

IS2 2.1'2 2p6 3s2 31~6 3d1o 4s2 4p6 4d1o 4jl4

I'" 3 only for f orbital.Thus the total number of orbitals for I'" 3 is equal to 7

(because f contains scvc~. orbitals).91. (b): 11; == CRT

c= RTtT 0.08~·~310=0.31 mol/L.

92. (b): C + O2 ~ CO2; !lH/ = - 490 kllmol x 8I

1-12 + "2 O2 ~ H20; Mll = -240 kllmol x 9SC + 18H -) CRHI8 ; Mil = +160 kllmol

. 98C + 802 + 9H2 + "2 O2 - 8C - 18H

~ 8C02 + 9H20 - CgHI8MI/ = -3920 - 2160 -160

25C~HIR + '2 O2 ~ SC02 + 9H20 ; !lfiO = 6240 kllmolMfa for 6 moles of octane == 6240 x 6 = 37440 kllmol.

93. (b): HP (f) ~ H20 (g)

This is a spontaneous process at standard conditionsthus, the standard free energy change must be less thenzero, i.e. !lGo < O.

94. (b): When a = b '* c, CI. = ~ == 90°, Y= 120°.The given condition is characteristic of hexagonal system.

95. (c): K = Ka, xKa2 =4.5xlO-3x1.7xIO-IO

=7.65x]0-IJ

[r·n=.JKE;:::; J7.65x 10-13 xO.OI

=,h65xlO-15 ",,0.87xI0-7

pH = -log 0.S7 x 10-7 == 7 - 0.93 == 6.07.96. (c): The given reaction is endothermic, so onincreasing the temperature, it will shift in forwarddirection.--------97. (c): In Daniel cell, during the passage of electriccurrent through external circuit, electrons flow fromthe zinc electrode to the copper electrode. At the zincelectrode, the zinc metal is oxidised to ZnH which go

AIIMS EXPLORER •

into the solution. The electrons released at the electrode 'travel through the external circuit to the copper electrode:where they are used in the reduction of Cu!' ions to 'metallic copper which is deposited on the electrode.98. (a): The substance which is susceptible of.degradation by biological processes, as by bacterial or ;other enzymatic action is known as biodegradablesubstance.'-------.~---~-~--~-- .....--..

k I I a (initial)99. (d): =- 11--:""""-'----t a-x(aftertimet)

k, = In [N20S]o[N20S],-------- ~------

100. (a) : Ozone depletion is caused by a number ofpollutants I ike chlorofluorocarbons (14% of totaldepletion), nitrogen oxides, sulphur oxides, CCI." Cl2etc. Maximum ozone depleting potential or OPD is ofchlorofluorocarbons (CF2CI2) due to release of chlorineby it. A single chlorine atom converts 1 lakh moleculesof ozone to oxygen.101. (b): Greater the number of negative atoms presentin the oxy-acid make the acid stronger.In general, the strengths of acids that have general formula,(HO)nrZOn can be related to the value of II. As the valueof II increases, acidic character also increases. The negativeatoms draw electrons away from the Z-atom and makeit more positive. The Z-atom, therefore, becomes more . 'effective in withdrawing electron density away from theoxygen atom that bonded to hydrogen. In turn, theelectrons ofH - ° bond are drawn more strongly awayfrom the H-atom. The net effect makes it easier fromthe proton release and increases the acid strength.

102. (c) : 24Cr ~ [Ar] 3cf 4s2

Cr ~ [Ar] 3cf54s1

Full-filled s-orbital has greater stability.

103. (d) : [Ni(en))]CI2 is a chelating compound andchelated complexes are more stable than similarcomplexes with unidentate ligands as dissociation ofthe complex involves breaking of two bonds rather thanone.In [Ni(en»)]CI2' Ni with d8 configuration shows octahedralgeometry. Six electrons will occupy the 12J( orbitals andtwo electrons will occupy the cl! orbitals.

104. (c) : Sb(lII) is a basic radical of lIB group forwhich group reagent is H2S in presence of dilute HC!.It is necessary to maintain the proper hydrogen ion


Solutions - 2004 415,,,-,.--,-,--.,,--~----------------------- ---------------

"concentration for the precipitation of lind group cations•' ~I:~~O check the pr:_ecipitation of IV group cations.

105. (d): Binding energy per nucleon of 3LF (5.38 MeV)is lesser than 2He4 (7.08 MeV) as helium is found to bemore stable than Li. As the atomic mass number increases,

, the binding energy per nucleon decreases. As the atomicnumber and the atomic mass number increase, therepulsive electrostatic forces within the nucleus increase

• due to the greater number of protons in the heavy clements.To overcome this increased repulsion, the proportionof neutrons in the nucleus must increase to maintain

., stability. This increase in the neutron-to-proton ratio onlypartially compensates for the growing proton-protonrepulsive force in the heavier, naturally occurring

- elements. Because the repulsive forces are increasing,, less energy must be supplied, on the average, to remove

a nucleon from the nucleus. The BElA has decreased.The BEl A of a nucleus is an indication of its degree ofstability. Generally, the more stable nuclides have higherBElA than the less stable ones. The increase in BElAas the atomic mass number decreases from 260 to 60 isthe primary reason for the energy liberation in the fissionprocess. The increase in the BElA as the atomic massnumber increases from I to 60 is the reason for the energyliberation in the fusion process, which is the oppositereaction of fission.106. (b) : Enamel, the hardest substance of the bodyis composed of fluorine not magnesium. Magnesium isan essential clement as it acts as a factor of many enzymesof glycolysis and a number of other metaboilic reactionsdependent upon ATP.

107. (c): Carboxypeptidase is an exopeptidase becauseit breaks the peptide chain at terminal ends.Carboxypeptidase cleaves carboxy-terminal amino acidsthat have aromatic or branched aliphatic side chains.108. (a) : Sucrose is a non-reducing sugar as it doesnot reduce Tollen 's or Fehling's reagent, due to absenceoffree aldehyde or ketone group. It contains stable acetalor ketal structure which cannot be opened into a free

.carboxyl group.Sugar is composed of a-D-glucopyranose unit and p-D-fructofuranose unit, These units are joined bya-l3-glycosid ic Iinkage between C-I ofthe glucose unit andC-2 of the fructose unit.-------------------------------

CI-fJ',109. (c): /CI'I-CI-IOCH) ..

Isobutanal has a-hydrogen atom .Acetaldehyde, acetone and methyl ketones having CH)COgroup undergo haloforrn reaction. The hydrogen atomsof the methyl group are first replaced by halogen atoms.This reaction is used as a test of CH3CO - group. Dueto absence of CH)CO - group isobutanal does not giveiodoform test.

110. HBr adds to the double bond of the styrene formingl-bromo-I-phenylethane.

styreneThis is an example of elimination-addition reaction.Note: Here given assertion is wrong.

Ill. (c): Lower the value ofpKa, more acidic will bethe compound. Acetic acid is more acidic than phenol.This indicates that carboxylate ion should be more stablethan the phenoxide ion and it is clear that carboxylateion has more equivalent resonating structures than thephenoxide ion.

112. (d) : 2-bromobutane on reaction with sodiumethoxide in ethanol gives 2-butene as a major product.

Etoii II ':'CH~ CH(CI-'3) L ~rt "CHJ

CHI J

EtOI-1+ CH = CH + Br"I

CI-IJThis is according to Saytzeff''s rule i.e. the predominantproduct is the most substituted alkene, i.e. are carryingthe largest number of alkyl substituents of hydrogen iseliminated preferentially from the carbon atom joinedto the least number of hydrogen atoms.2-butene is more stable than I -butene due to presenceof large number of hyperconjugating structures in 2-butene.

113_ (a): C611,cJ-lzOCH3~ C61-lsCI-iz+ CHpH

!1-

C6H7CH21This can be explained on the basis of SNI mechanism,the carbonium ion produced being benzylium ion, sincethis type is more stable than alkylium ion.


114. (b) : Molar entropy of vaporization of water ismore than ethanol, as water has greater forces of attractionthan ethanol.

11S. (a): The colour of colloidal solution depends 011

the wavelength of'Iight scattered by the dispersed particles.The wavelength oflight further depends on the size andnature of tile particles. The colour of colloidal solutionalso changes with the way the observer receives the light.Finest gold sol is red in colour. As size of the particlesincreases, it becomes purple, then blue and finally goldenyellow._ .._---- -----116. (d): Copper corrods at negligible rates in unpollutedair, water and deaerated non-oxidising acids. Pure copperand the high copper alloys call be considered to exhibit

.r similar resistance to most corrosive environments. Theypossess excellent resistance to atmospheric environments.(corossion is a spontaneous process for which free energychange must be negative.._._----------------- ------t t 7. (c) : K,p of AgCl > K,I' of AgBr.For the precipitation to occur, its ionic product shouldexceed solubility product.------118. (b): Zeolites are shape-selective porous solid acidcatalysts, their catalytic activity originates from thepresence of highly acidic Al - O(H) - Si hydroxyl inthe framework.___ • __ ~_~.~ •• u __ ._·. __ •__ .·_· • •• ~

119. (c): Due to greater lone pair - bond pair repulsionsthan bond pair - bond pair repulsions, the F - S - Fbond angle decreases from 1800

•-.-----,-~--- ...,.-~.,,-120. (c) : Molecular size decreases from left to rightwhile it increases in a group from top to bottom. Thusmolecular size of nitrogen is greater than oxygen.

_ i BIOLOGY " '. -.

121. (d): Cotton and other monocultured crops requirean intensive lise of pesticides as various types of pestsattack these crops causing extensive damage.So far, the only successful approach to engineering cropsfor insect tolerence has been the addition of Bt toxin.a family of toxins originally derived from soil bacteria.The Bt toxin contained by the Bt crops is no differentfrom other chemical pesticides, but causes much lessdamage to the environment. These toxins arc effectiveagainst a variety of economically important crops pestsbut pose no hazard to non-target organisms like mammalsand fish. The Bt gene was isolated and transferred from

AIIMS EXPLORER

a bacterium Bacillus thuringiensis to American colton.The American cotton was subsequently crossed withIndian cotton to introduce the gene into native varieties.Bt toxin protects the colton plants from ballworm(A. lepidopteras. a major pest of cotton. The worm feedingon the leaves of a Bt cotton plant becomes lethargicand slecpy, thereby causing less damage to the plant_._--------_",._._._----122. (b): The ventral nerve cord. as its name suggests,is a cord of nervous tissue that runs the length of theanimal in the lower part of its body. It is the characteristicof lower chordates like leech, cockroach and scorpion.-------_-- ...-.~-..~~~---~~--.~~-~~-.~.--~~.~~-~123. (<I) : A synapse occurs where the axon of oneneurone (the pre-synaptic neurone) meets either thedendrite or the cell body of another (the post-synapticneurone). At the tip of the pre-synaptic axon is a buttonshaped swelling called a synaptic knob, inside whichare numerous mitochondria and vesicles packed with asubstance called a neurotransmitter is present.This neurotransmitters at the time ofncrve impulse diffuseacross the space and bind to receptors in the membraneof the post-synaptic cell. This opens ion channels inthe post-synaptic membrane of the [lost-synaptic cellresulting in a change in the post-synaptic cell's membranepotential and (if the cell is sufficiently excited) in theconsequent generation of a nerve impulse.

124. (d) : The two DNA strands are held together byweak (hydrogen) bonds between the bases on each strand,forming base pairs. Genome size is usually stated asthe total number of base pairs: the human genome containsroughly 3 bill ion base pairs.

125. (c) :The great Barrier Reef - the largest systemof coral reefs in the world - is more than 2,000 km illlength and comprises 2,900 separate reefs and 940 islands.Its high species diversity includes more than 400 speciesof coral, 4,000 species of molluscs, 1,500 species offish, 6 species of turtles, 35 species of seabirds and 23c

species of sea mammals. The Great Barrier Reef is oneof the richest and most complex natural systems in theworld. The Reefs diverse range of habitats all connectand support each other, which means they are al t vitalto the life of the Great Barrier Reef.

126. (d) : The species or taxa, which arc in dangers ofextinction and which may not survive if the adverse factorscontinue to operate or the species whose numbers havebeen reduced to a critical level or their habitats have


Solutions - 2004

been drastically reduced in such a way that they are ininstant danger of extinction arc called endangered species.

· In India, aconite and horn bill are endangered species._'w_.·.·· ·. · · ····· _

1.27. (a): Amphetamines arc powerful drugs (stimulant),they 'speed' up the whole body. increasing the heartrate, blood pressure and breathing. Amphetamines makethe user feel excited, confident and energetic. Some peopleuse amphetamines to suppress their appetite, so they

: can go for a long time without eating. There are many· health risks from taking this type of drug. Long-term

usc can cause mental illness and will put a strain on the· heart, due to increased blood pressure .

...... ,.,. ,.,-----,~.-.-.....-------."~..-~-.---~-----.---~-_-.-"-_"-_'--128. (b): SA node or sino-atrial node is known as thepacemaker of heart because the cells in the SA nodecontract the most number of times per minute and becauseeach wave. of excitation begins here and acts as thestimulus for the next wave of excitation.

129. (b): The photosynthetic bacteria (e.g. purple non-sulphur bacteria) photosynthcsise using bacter io-chlorophylls a and b in anoxic environments, such as

. the bottom mud of ponds and other stagnant water,although they are able to survive in air. The reducingagent involved is hydrogen rather than water, so oxygenis not produced. These bacteria efficiently use infraredlight for photosynthesis.

130. (c): There are some rare cases in medical literationwhich could be interpreted as atavisms, that is thereappearance of our ancestor's organs, in which moreprolonged traits, already lost by human beings throughoutevolution, are expressed again. Such is the case of~.~T~'~I:t.l~ler~:.!:r_mamm~y glan~~~:_.:~cral tail etc.13]. (1I): The Virus Research Centre (VRC), Pune cameto existance in 1952 under thejoint auspices of the ICMR

and the Rockefeller Foundation, as a part of the globalprogramme of investigations on the arthropod - bornegroup of viruses. In view of its expanded scope andactivities, the YRC was undesignatcd as the NationalInstitute of Virology (NIV) in 1978. The NIV is identifiedtoday as the WHO collaborating centre for arbovirusreference and research. N IY also acts as the National~!_~~~~{)::~~gS'en~:._~or (nt1L::I~~ and ~I_:.e~titis. .132. (c): Electron Beam Therapy or radiation therapyinvolves the lise of radioactive waves to treat certaintypes of cancer. The therapy can be given with externalbeams of radiation. Electron beams arc of low energy.

417

They arc often used in skin conditions and cancers. Theprocedure to deliver external beam radiation is somewhatsimilar to giving an X-ray. The person is put into position,and the machine delivers the radiation to the desiredarea. This beam therapy involves iodine, cobalt, protonsand electrons. This therapy is used in cancer of cervix,cancer of larynx, germ cell cancer, Hodgkin's lymphoma,~_~t.~~e canr:.:.r~..breast can:cr, IU!lJL~~,~~_::_~_. _133. (b): SARS (severe acute respiratory syndrome)has now affected 30 countries on five continents, withmore than 8,000 cases and more than 900 deaths. Thedisease is due to infection with the SARS coronavirus(SARS-CoV). The genome of this virus has beencompletely sequenced. When viruses resembling SARS-Co V were isolated from Himalayan palm civets foundin a live animal market in the Guangdong Province ofChina; it implicated these animals as the reservoir ofthe virus.

134. (c): A better understanding or the mode of actionof vitamin K is made possible by the use of an anti-coagulant. One such naturally occurring antagonist ofvitamin K is known as Dicumarol. The discovery of theanti-coagulating properly of Dicurnarol took place whenit was established that consumption of improperly curedsweet clover hay caused cattle to develop the so-called"sweet clover disease" which is attributable to a seriousalternation in the coagulability of the blood that, in turn,~'ten r:~ult in fat~_~~~ell1orrhage.135. (c)--------136. (b) : Sulfur and nitrogen oxides emitted into theatmosphere react to form compounds that arc transportedlong distances and arc subsequently deposited to theEarth's surface in wet and dry forms. Although the term"acid rain" is widely recognized, the dry deposition portionranges from 20 to 60 percent of total pollutant deposition,and represents the particulate and gaseous forms. A moreaccurate description of tile overall process is aciddeposition rather than acid rain.Dry deposition occurs when sulfur dioxide and nitrogenoxides react, but not with water. It settles out of theatmosphere as particle or gases.The effects of acid deposition include acidification oflakes and streams, nutrient enrichment of coastal watersand large river basins, soil nutrient depletion and declineof sensitive forests, agricultural crop damage, and impactson ecosystem biodiversity. Toxic pollutants and metals


also can be transported and deposited through atmosphericprocesses. Both local and long-range emission sourcesc?ll.~I~~ute..~~..~t.~~~?~pheric~positio_n_. _137. (c): Domestic sewage rich in organic waste willexert a very high demand of oxygen in order to getbiodegraded. Thus depleting the dissolved oxygen belowcritical level necessary to support aquatic life. Especiallyfish, which is very sensitive to the dissolved oxygenavailable in water, starts dying if the level goes below4 mg/L .. ---.-------~-..138. (h) : The Minamata disease got its name fromMinarnata Bay in Southwestern Japan where it was firstobserved in nearby communities. It was officiallydiscovered in 1956, and a few years later it was knownto be caused by ingestion of fish that had beencontaminated by mercury left off from a chemicalmanufacturing plant. Levels of methylmercury chloridewere very high: upto 50 ppm in fish and 85 ppm inshellfish from the contaminated areas. 121 people werepoisoned from eating the contaminated fish, 46 ofwhichdied. Dogs, cats, pigs, rats and birds that were livingaround the bay also showed the signs of mercurypoisoning, and many died.The initial symptoms were numbness of the limbs andthe area around the mouth, sensory disturbance, anddifficulty with everyday hand movements. Also thereoccurred a lack of coordination, weakness and tremor,slowed ami slurred speech, and altered vision and hearing.These symptoms worsened and led to general paralysis,involuntary movements, difficulty in swallowing,Co.l~V~ll,!~,i,.'::~l.~:_~~~da~~~e al~_9.:_~,t~,_ ..139. (c): A pacemaker (or "artificial pacemaker"), isa medical device designed to regulate the beating ofthe heart. The purpose of an artificial pacemaker is tostimulate the heart when either the heart's nativepacemaker is not fast enough or if there are blocks inthe heart's electrical conduction system preventing thepropagation of electrical impulses from the nativepacemaker to the lower chambers of the heart, knownas the ventricles. Generally, pacemakers do not treat fastrhythms of the heart.~-,---.--.~- ....¥--... . ._--_._---I~O. (c) : On September 14, 1990 researchers at theU.S. National lnstitutcs or Health performed the first(approved) gene therapy procedure on four-year old:\ shanti DeSilva. Born with a rare genetic disease calledsevere combined immune deficiency (SeIDl, she lacked

AIIMS EXPLORER,

a healthy immune system, and was vulnerable to everypassing germ. Children with this illness usually developoverwhelming infections and rarely survive to adulthood.In this gene therapy procedure, doctors removed white.blood cells from the child's body, let the cells grow in .the lab, inserted the missing gene into the cells, and.then infused the genetically modified blood cells backinto the patient's blood stream: Laboratory test have~~lown that the therapy strengthened her immune system~

141. (a): After entering the wall of the embryo sac thepollen tube during its entry into the embryo sac.passes through the nucellar cells and the synergids, '.e.g. Fagopyrum. The pollen tubes passes between theegg and one synergid. In Cardiospernnnn; it passesbetween embryo sac wall and synergid, In Oxalis, it passesdirectly through a synergid. In Viola it enters a synergidand makes its way through the base of the synergid. Innormal cases only one synergid destroys by the impactof the pollen tube and the other remains intact untilsometimes afterwards.---.-~.------142. (d): Southern blotting was named after EdwardM. Southern who developed this procedure in EdinburghUn iversity in the 1970's. Southern blotting is designedto locate a particular sequence of DNA within a complexmixture. For example, Southern Blotting could be usedto locate a particular gene within an entire genome.The amount of DNA needed for this technique isdependent on the size and specific activity ofthe probe.Before, starting the procedure, the desired DNA should~~ isolated from a specific nucleated cell.143. (<I): Even a single dose of thalidomide can causesevere birth defects or fetal death, thalomid (a form ofthalidomide) must not be used during pregnancy.Pregnancy must be ruled out 24 hours before startingtherapy with thalidomide. Women must be monitoredfor pregnancy while using thalomid because it can giverise to underdeveloped limbs in fetus.144. (d)

145. (c): During inversion a segment of chromosomegets inverted in the process of reattachment. Thus achromosome having the genes ABC D E F G H I inlinear order may get the segment D E F inverted. Thenew arrangement will be ABC FED G H I. It is achromosome aberration entailing two breaks in achromosome followed by a reversal of the segment andconsequently of the gene sequence ill the segment.


Solutions - 2004 419._---- ._--_.._ .._--_. __ .__ .. _ _._-_._ __._ _--_ _.__ ._ -_._-_ _._. __ ._._ __ ._ .._ .._--_ _-_. __ .._..

Periccutric inversion includes the centromere in theinverted segment, whereas paracentric inversions do not.------.~~.146. (b)

147. (b): Passive immunity may be artificially acquired,particularly when antiserum or antibodies produced byone individual are transfused into a second individual.In all cases, passive immunity represents the passiveacquisition of an immune response that was activelyacquired by another individual. Passive immunity canlast for at most months since antibodies have a finitelife span within the body.

148. (b): Pseudomonas aeruginosa is a Gram-negative,aerobic rod belonging to the bacterial familyPseudomonadace ae. These bacteria are commoninhabitants of soil water. They occur regularly on thesurfaces of plants and occnssionally on the surfaces ofanimals.• The bacterium will grow in the absence of O, if

NO) is available as a respiratory electron acceptor.P aeruginosa possesses the metabolic versatil ity,Organic growth factors are not required, and itcan use more than thirty organic compounds forgrowth.Pseudomonas aeruginosa is often observed growingin "distilled water" which is evidence of its minimal

o

•

•nutritional requirements.It is able to grow at temperatures as high as 42degrees.

o Its tolerance to a wide variety of physical conditions,including temperature, contributes to its ecologicalsuccess and makes it suitable for decomposing avariety of organic compounds in variedenvironmental conditions.

149. (c) : DNA is present both in mitochondria andchloroplast. The DNA molecules are circular, relativelysmall, double stranded (except for the DNA of somealgae and protozoans), The mitochondrial DNA variesin size starling from 5 urn to 30 urn. Average length ofchloroplast DNA is 45 urn.-..----.-~--.-.---.-- ..---.---- .~_;__~~~-~~~~.~~~-

150. (c) : Cytokinins are a group of phenyl ureaderivatives of adenine, one of the molecules in DNAduring pruning axillary bud, which is under repressiondue to effect of auxin, get sensitized to cytokinin, whichreleases it from apical dominance,Cytokinin functions• Cytokinins promote cytokinesis. They are found

primarily in root meristcms, embryos and fruits, andmigrate from roots to the shoot systems of plants inxylem tissue.o Cytokinins can promote axillary bud growth byover-riding the apparent inhibiting effect of auxin. Thisis one of the ways in which plants balance root andshoot growth. Shoot tip auxins inhibit lateral budactivation. Cytokinins produced in root meristerns travelupward in xylem and if in higher concentration counterthe inhibition of auxins to activate lateral buds.o Cytokinins also retard leaf senescence, probablyby stimulating RNA and protein synthesis and delayingdegradation of chlorophyll.__ • •• ~__ ._._. ._ ••_,·,v_ ••_...

151. (a): Guard cells arc semilunar or kidney shaped. cells which surrounds the minute apertures of epidermiscalled stomata. Guard cells are living and have chloroplast.In sugarcane and in some other monocots like doob,maize guard cells arc dumb bell shaped.....__ .-----------_-_-----------------_._---_ ..

152. (b): Analogous organs are those organs, whichare different in origin but similar in function. Potatoand sweet potato are absolutely di fferent in their originas potato is modified underground stem (tuber), whilesweet potato is tuberous root. It means both have edibleparts,_whic~,Ir.:~~i_.!:!~re.I~!~.r~~I!:.~:__.. . .__~_.._._.._.153. (c): In Ulolhl'ix sexual reproduction is of isogamoustype. Two isogametes of + and - strain come togetherand fuse as a result a quadriflagellate zygospore is formedwhich floats 011 water after sometime it rests on the bottomof the pond at this time its four flagella disintegrateand a wall is formed surrounding it from all sides. Aftertaking rest for a long period this zygote divides meioticallyand gives rise to 16 zoospores. These zoospores comeout of sac and give rise to the ncw plants of Ulothrix.154. (d) : Due to continued formation of secondarytissues in the older stern and roots however the epidermisgets stressed and ultimately tends to rupture and followedby death of epidermal cells and outer tissues, and a new

protective layer is developed called periderm. Structurallyit consists of three parts Phellogcn or Cork cambium,phellern or cork and phelloderm.Usually in the periderm of most plants. certain areaswith loosely arranged cells have been found, whichpossess more or less raised and corky spots where till'underneath tissues break through the epidermis. SUL"l~

areas are universally found in the stems of woody plaru».These broken areas are called lenticels, which perform


the function of exchange of gases in the absence ofstomata.155. (c) : Sornaclonal variation refers to all types ofvariation occur in plants regenerated from cultured cellsor tissues. Genetic changes take place in plant tissueculture and these changes arc passed to their progenies.This technology can be used for disease resistance,illlprovement of ql~ality and yield in ~!ants. ~~~

156. (d)',"'" -~-----.---,---t 57. (c): The companion cells occur only in angiospermswhere they accompany most sieve tube clements.Companion cell is a speciliased type of parenchyma cellwhich is closely associated in origin, position and functionwith sieve tube clements. These cells are living havingabundant granular cytoplasm and a prominent elongatednucleus, Usually, the nuclei of the companion cell servefor the nuclei of the sieve tubes as they lack them. Thecompanion cells do not contain starch. They live onlyso long as the sieve tube clement with which they areassoc iatcd and they are crushed with those cells.Longitudinal division of the mother cell of the sievetube element forms the companion cells. One daughtercell becomes a companion cell and other sieve tubeclement.---- ----------~~t 58. (a) : During fertilization ventral canal cell andthe neck canal cell, along with tip of the neck disintegrateand the neck forms a canal like passage full of mucilageand some chemicals like malic acids. These chemicalsattract antherozo ids (chemotactic movement 0 fantherozoids) and one of the male gametes fuses withthe oospore forming a diploid oospore. Water is essential

!?r_~~,~_I~'~<:c~___ '"._~~~ __159. (b): Corkcambium is a secondary lateral meristemthat may arise from permanent living cells of hypodermisor outer cortex. It is composed of a single layer ofmeristcmatic cells. Its cells divide tangentially andpericlinally toward the outer face and produce cork cells.These cells arc compactly arranged and have thin cellulosewalls in the beginning. As they mature there is a gradualloss of living matter and cells get elongated radially,vertically or tangentially. The cell walls become thickbecause of development of fatty substance called Suberin,which .~.!,mpervious _to~\V_a_t_er_.~~__ ~ __ ~~_

AABBCC x aabbcc P

<>AaBbCc FI

160. (b) :

AIIMS EXPLORER

:. Number of heterozygote is 3., Number of progenies in F I will be 2" or 23 = 8.161. (a) : DDT or dichloro-diphenyl trichloroethanewas the first important synthetic pesticide (organochlorine) discovered in 1939 by a Swiss chemist PaulMuller. It was toxic to wide range of insect pests ("broadspectrum") yet appeared to have low toxicity to mammals.It was persistent i.e. didn't break down rapidly in theenvironment, so that it didn't have to be reapplied often.DDT was so effective at killing pests and thus boostingcrop yields and was so inexpensive to make that its use.quickly spread over the globe. Farmers used more andmore DDT throughout the 1950s and 1960s to get anincreased yield of crop.--.---~-,.~---~---162. (b): Antidiuretic hormone (ADH) or vasopressinis secreted from posterior pituitary gland. it is releasedin response to a fall in the water content of blood plasmaand lead to an increase in the permeability to water ofthe distal and collecting tubules ofthe nephron. Deficiencyor hyposecretion of ADH results in diabetes insipidus.Diabetes insipidus is characterised by micturating diluteurine several times a day which results in excessive thirst(polydipsia) and dehydration.163. (c): Oparin and Sydney Fox held that large organicmolecules synthesised abiotically on primitive earth andformed large colloidal aggregates due to intermolecularattraction. These colloidal partie Ies were call edcoacervates, In coacervates, lipid molecules are joinedend to end forming a layer around each aggregate. Thisrepresents a single lipid membrane. Coacervates divideby budding like bacteria.. . ---------~--~--164. (c) .Tnpcworm belonging to phylumplatyhelrnimhes, pinworms and roundworm belongingto phylum nematoda, arc all endoparasites. They all areintestinal parasites. In case of Taenia solium man getsinfection by uncooked or improperly cooked measly pork.Cysticercus becomes active on reaching the intestine.Proscolex everts or evaginates in the intestinal wall.Ascaris, being an endoparasite inhabits the small intestineof man, more frequently of children than of adults. Mangets infection through skin contact. Enterobiusvermicularis or pinworm live in caecum, appendix andat the junction of large and small intestine. They aretransmitted by the in~proper sanitary condition.165. (c): The fish meal is prepared from the wastes offish oil or canning industry or from the whole fish of

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non-oil type. The protein content ofthis meal is highlydigcstablc, nutritive and of biological importance. Fishmeal is also used for domestic animals like pigs, poultry,cattle ere.

16(1. (1)): Adaptation is the most basic and rather self-evident concept. It is the morphological or physiologicalmodification in an organism to adjust itself in a particularenvironment. In some animals, it is known as mimicryas for example praying mantis or stick insect. The stickinsect or praying mantis having green body colour exhibitsclose resemblance with twigs and foliages. It is a typeof protective mimicry. They exhibit close resemblancesalso with the twigs in having slender body, attenuatedlimbs, sympathetic colouration and slow movement.""_~ __ ' ~_'_~~_'_'_~~~"""_' __ '_"_"_'_' __ "'M_'_' •• _ •.'••.•• __ .•. ."._ ••_, ._

1(,7. (a): Carolus Linnaeus called humans as Homosapiens or wise men and placed them along with apesand monkeys. There arc certain similarities betweenhuman lind chimpanzee. These arc -(i) RNA content of diploid cells is similar(ii) DNA matching shows that human similarity is 100% with chimpanzee and(iii) banding pattern of chromosomes shows very littledifference in chromosomes 3' and 6 between humansand chimpanzee.Thus it can be concluded that among the primates,chimpanzee is the closest relative of the present day

.humans.

. 168. (d): Dope test is an official test to discover whethera person or an imal taking part in a competition has beengiven any drugs (such as anabolic steroids, erythropoietinetc.) to make their performance better or worse. It is atype ofblood test. Alcohol is not used in this purpose.Alcohol has an effect 011 cerebellum and it results intoi~~l.~~..~I.I.~!~ed n~~_c~I~~_l!:a~~.':.~ti~~,_~~~ure etc. __ .,,_...__169. (b): Queen is the only fertile female in beehive,having immensely developed ovaries. She lives for severalsuccessive years laying about 2000 or more eggs a dayand upto about 1,500000 eggs during her life time. Thequeen has a remarkable capacity of controlling thefertilization of its eggs. A fertilized egg is laid ina workeror queen cell or honey comb, while an unfertilized eggill a drone cell, the latter develops parthogcnetically,The queen mates only once in a life time. The spermsstored in her spermathcca fertilize her eggs as long asshe lives.

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170. (d): Assertion is false as the humans would requiremore gestation period (should have been 21 months ascompared to 9 months and wi II increase). Simi larly thehead size is increasing (especially the frontal brain) hencegrowth rate needs to increase but surprisingly most ofthe brain growth occurs after birth till 2 years (whenthe arterior fonranellae close at i8 months) and somemore till 30 years when finally the cranial sutures close.Thus an increase in brain/skull size would requiredincrease in gestation period, hence both assertion andreason are false.~.:--.------.--._----.-..-.-.-~..~.-..-..-.-.---- ..---:'''-.-_.171. (a): The Darwin Wallace theory of NaturalSelection can be generalised as ihe change in speciesby the survival of an organismal type exhibiting a naturalvariation that gives it an adaptive advantage in anenvironment. Thus leading to a new environmentalequilibrium, The idea of the survival of'the fittest explainthe above evolution by natural selection. According tosurvival of fittest, some of the variations exhibited byliving things make it easier for them to survive andreproduce thus more adaptive forms increase. Those which

~l!:.~_!_l_~~..~~t._~?_~_l_~~adap~0~~l~.:.:.~~~~..~..~.~~.1~ina t~.~..'. ..._,172. (b): Rhizome is normally a prostrate, thickenedstem, creeping horizontally under the surface of the soil.The common example is ginger. It is provided with distinctnode and long or short internode. It bears some scalyleaves at the nodes, possesses a bud in the axil of thescaly leaf and ends in a terminal bud .The response of plant to gravity is called geotropism.The roots arc positively geotropic and grow downwards,while the shoot is negatively geotropic and grows awayfrom the gravitational pull from the centre of earth. Parts~~~icl~_~~.?.wIlo~ffcct 0r._¥.~'.:~ityarc call~~:~.!l:_~rop~~173. (c): Flowering is a phytochrome regulated process.Phytotchrome is a blue protein pigment with a molecularmass of about 125 k DOl(kilodaltons). Phytochrome occursin two interconvcrtible form Pit (which absorbs red light)and PFIt (which absorbs far red light). The studies withmutants of Arabidopsis support and prove that the Pmis the active form of phytochrome. When PI( moleculesarc exposed to red light, most of them absorb it andconverted to P!'R' This causes floral induction in theshoot. A night interruption inhibits flowering of short-day plants and promotes flowering of long-day plants.Red light is more effective with short-day plants and amixtur.:._.?f red and ~~-:.:.:~~!..~~~~~¥:_day.....E..~:nts.__


light energy and the catalytic action of chlorophyll. water,a substance oflow energy value. is split up into oxygen Iand hydrogen. Oxygen is used in the ch loroplast, NOll-cycl ic photophosphorylation is the only natural process I~~~~~~~\dds ll1olec~~~~.~.~!.]:_I~~~~ atmosphere. It 75. (d): Symbiotic nitrogen fixation occurs in legume i

plants. It takes place in the Rhizobitnn bactcroids wh ieh I'

arc located within root nodules cells. Rhizobium is anaerobic bacteria and hence it survive in presence of Ioxygen. [3lH the important enzyme Nilrogell(ls{' i(syn~l~csise by Rhizobimu) that reduces N". is oxy~cn iscnsruvc. It e,1I1only function at low oxygen COIlCenIlTltIOI1..This low oxygen concentration ill bactcriod is providedby lcghacrnoglobin. l.cghaernoglohi n (pink in colour)is a form of haemoglobin round in the nitrogen fixingroot nod ulcs of legume. They bound oxygen and thusprotect the nitrogen fixing enzyme. nitrogenase Ithat isoxygen sensitive). It regulates oxygen diffusion to __ C~ _

buctcroids and nitrogenase. I' 80 I S....... _ _........... I . (J) : Superovulation is an effort to increase the176. (a): In some species of red algae called coralline fertility of caulc breeds. Inducing an animal to ovulatealgae, the cell walls become hardened with calcium I multiple oocytcs can translate into producing morecarbonate. These algae hence important for the formation I offsprings from selected females. Superovulation andof coral reefs. I embryo transfer involves the following steps.Coral reefs arc formed throuch the accumulation of I. Donor cows of particularly tine pedigree arc treatedcalcareous exoskeletons of corul animals. calcareous red I with hormones (mainly FSH and LH) to increase thealgae and molluscs, They form the foundation of reefs number of eggs released at ovulation - multiple ovulationby sccrcti I1g a calcium carbonate skeleton that provides (MO)protection for the coral polyps. Calcium carbonate is • The cows arc artificially inseminated using semen

sccrete.~I ...:?~l!inu?~I~IL~?: th:.:orill (;()I(.jI1Y. from a proven bull• After 6 - 7 days the embryos arc flushed out non-surgically, using a catheter placed into the uterus. Thisis possible because. in cattle, there is delay in embryosbecoming implanted in the uterine wall. On average. 4-7 embryos arc collected.• The embryos may then be implanted into recipientcows whose oestrous cycle is at the correct receptivestage - usually as the result of hormonal manipulation.• Embryos may be frozen and stored, using techniquessimilar to those applied to semen. (though precise controlof the regime is somewhat 1110["ecritical).Farmers may, of course, buy-in embryos from sourcesanywhere in the world to transfer to their OWI1 recipient

'422

t 74. (h): Cyclic pathway of photosynthesis is appearedfirst ill some euhactcrial species. It is supposed to bethe first evidence 0 f production or ATP in the presenceof light. During non-eye Iic photophosphorylationphotolysis ofwater takes place. Under the influence of

177. (d) : Insect visit flowers to get nectar. Nectar iscontained in a special gland called nectary and sometimesin a special structure called spur.The attraction of' flower in plants is not to diverge theinsect 11'0111 damagiug other part. but to bring aboutpollination (i.e. transfer of pollen to the stigma). Thepollen grains in insect pollinated flowers are'either sticky0[" provided with spinous outgrowths. The stigma is alsosticky. Insect often visit these flower for nectar and

178. (b): Coconut require the hot and wet climatehence it is grown in coastal areas. It is widely grown incoastal a IIII dcltic regions of tropical and subtropical

AIfMS EXPLORER

countries,Coconut fruit show hydrochory i.e . the dispersal takesplace through water medium. Being the habitant of coastalarea the fruit is so adapted that it can float and dispersedover thousand of kilometers before losing viability.179. (c) : Sulphur is not a constituent of ch lorophyllbut it helps in chlorophyll formation. Due to the deficiencyor sulphur, ch lorosis often appears first in the youngleaves. Mineral constituent of chlorophyll is magnesiumwhich is situated in the centre of thc porphyrin ri ng,

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Embryo transfer has the potential to bring aboutgeneric improvement twice as fast as AI (ArtificialInsemination) alone.

III J. (d)

183. (b)

185. (a)

182. (a)

184. (C).______ ,_,_, ._~.~ r_~'_______ , ·'r.~ __._••_,_r_r._,,_,_.

186. (a).•...••••• - •• _••• _ .••. _, •. ,"._. .'_"__ '",, , '•• ' • __,,_••·•__ ._ n'.__ ."" •.,.•~ __

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189. (<I)

191. (b)

193. (c)

195. (b)

191. (a)

194. (<II

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198. (<I I197. (b)

199. (a)

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