BSc CSIT Entrance Exam 2071 Questions with Answers

1. a$7$ and $-1$
2. b$7$ and $1$
3. c$7$
4. d$1$

Answer (a): $x-3=4$ gives $x=7$, and $x-3=-4$ gives $x=-1$.

Revise: Algebra (Class 11 notes)

1. anull set
2. b${3}$
3. c${3,-3}$
4. d${4,3}$

Answer (a): $x-x^2=9$ means $x^2-x+9=0$, whose discriminant $1-36<0$ gives no real root, and $2x=6$ gives $x=3$ which does not satisfy it. So the solution set is empty.

Revise: Algebra (Class 11 notes)

1. a$0$
2. b${-1,1}$
3. c${1,0}$
4. d${4,3}$

Answer (b): $f^{-1}(4)$ is the set of $x$ with $x^2+3=4$, so $x^2=1$ and $x=\pm1$.

Revise: Algebra (Class 11 notes)

1. a$0$
2. b$\frac{3}{2}$
3. c$-\frac{13}{12}$
4. d$\frac{\pi}{6}$

Answer (b): $\log_2 2^{1/2}=\frac12$, $\log_3 3^{1/2}=\frac12$, and $\log_4 2=\frac12$, so the sum is $\frac32$.

Revise: Algebra (Class 11 notes)

1. a$n\pi\pm\frac{\pi}{4}$
2. b$n\pi+\frac{\pi}{4}$
3. c$n\pi\pm\frac{\pi}{3}$
4. d$2n\pi$

Answer (a): $\cos\theta=\pm\frac{1}{\sqrt2}$, so $\cos^2\theta=\cos^2\frac\pi4$ and $\theta=n\pi\pm\frac\pi4$.

Revise: Trigonometry (Class 11 notes)

1. a$\frac35$
2. b$\frac45$
3. c$\frac{9}{25}$
4. d$\frac{4}{25}$

Answer (b): Let $\sin\alpha=\frac35$; then $\cos\alpha=\sqrt{1-\frac{9}{25}}=\frac45$.

Revise: Trigonometry (Class 11 notes)

1. a$2a^2c^2=b^2(a^2+c^2)$
2. b$a^2c^2=b^2(a^2+c^2)$
3. c$2b^2c^2=a^2(b^2+c^2)$
4. d$c^2a^2=2b^2(a^2+c^2)$

Answer (a): Reciprocals are in A.P.: $\frac{2}{b^2}=\frac1{a^2}+\frac1{c^2}=\frac{a^2+c^2}{a^2c^2}$, so $2a^2c^2=b^2(a^2+c^2)$.

Revise: Algebra (Class 11 notes)

1. a$0$
2. b$4$
3. c$1$
4. d$-4$

Answer (b): $A^2=\begin{pmatrix}5&8\8&13\end{pmatrix}$. Comparing the $(1,2)$ entry: $8-2n=0$ so $n=4$ (and $5-n-1=0$ agrees).

Revise: Algebra (Class 11 notes)

1. aSymmetric
2. bSkew-symmetric
3. cSingular
4. dNonsingular

Answer (d): Expanding along the first row, $|A|=1(0-0)-0+1(0-1)=-1\neq0$, so $A$ is nonsingular. It is not symmetric since $a_{23}\neq a_{32}$.

Revise: Algebra (Class 11 notes)

1. aConsistent and dependent
2. bInconsistent and independent
3. cInconsistent and dependent
4. dConsistent and independent

Answer (b): The second equation reduces to $2x+y=4$, which contradicts $2x+y=5$, so the system has no solution (inconsistent). The equations are not multiples of each other, so they are independent.

Revise: Algebra (Class 11 notes)

1. a$1$
2. b$-1$
3. c$-i$
4. d$-i+1$

Answer (d): $i^7=i^4\cdot i^3=-i$ and $i^4=1$, so the sum is $1-i$.

Revise: Algebra (Class 11 notes)

1. a$w$
2. b$x+y+z$
3. c$w^2$
4. d$1$

Answer (a): Multiply the denominator by $w$: $w(y+wz+w^2x)=wy+w^2z+x$ since $w^3=1$. That is the numerator, so the ratio is $w$.

Revise: Algebra (Class 11 notes)

1. a$0$
2. b$4$
3. c$16$
4. d$-4$

Answer (b): Equal roots need $16-4k=0$, so $k=4$.

Revise: Algebra (Class 11 notes)

1. a$\frac{a_1}{a_2}=\frac{b_1}{b_2}=\frac{c_1}{c_2}$
2. b$\frac{a_1}{a_2}=0$
3. c$\frac{b_1}{b_2}=0$
4. d$\frac{c_1}{c_2}=0$

Answer (a): Two lines coincide exactly when all three coefficient ratios are equal.

Revise: Analytic geometry (Class 11 notes)

1. a$2$
2. b$-2$
3. c$0$
4. d$1$

Answer (b): A pair of lines $ax^2+2hxy+by^2=0$ is perpendicular when $a+b=0$. Here $2+k=0$, so $k=-2$.

Revise: Analytic geometry (Class 11 notes)

1. a$x^2+y^2-4x-4y+4=0$
2. b$x^2+y^2+4x+4y+4=0$
3. c$x^2+y^2-4x+4y+4=0$
4. d$x^2+y^2-4x+4y-4=0$

Answer (a): The centre is $(2,2)$, so $(x-2)^2+(y-2)^2=4$, which expands to $x^2+y^2-4x-4y+4=0$.

Revise: Analytic geometry (Class 11 notes)

1. a$25$
2. b$-25$
3. c$\pm25$
4. d$\pm1$

Answer (a): The point $(3,4)$ lies on the line, so $k=3(3)+4(4)=25$.

Revise: Analytic geometry (Class 11 notes)

1. a$80$
2. b$40$
3. c$10$
4. d$0$

Answer (a): Using $\lim_{x\to a}\frac{x^n-a^n}{x-a}=na^{n-1}$: $5\cdot2^4=80$.

Revise: Calculus (Class 11 notes)

1. a$7$
2. b$3$
3. c$11$
4. d$4$

Answer (c): $3+4\cdot\frac{\tan2x}{x}\to3+4\cdot2=11$.

Revise: Calculus (Class 11 notes)

1. a$xb^{x-1}$
2. b$b$
3. c$x^b\ln|b|$
4. d$b^x\ln|b|$

Answer (d): $\frac{d}{dx}b^x=b^x\ln b$.

Revise: Calculus (Class 11 notes)

1. a$\frac{\sin(\cos\sqrt x)\sin\sqrt x}{2\sqrt x}$
2. b$\sin(\cos\sqrt x)$
3. c$\sin(\sin\sqrt x)$
4. d$\frac{\sin(\cos\sqrt x)}{2\sqrt x}$

Answer (a): Chain rule: $-\sin(\cos\sqrt x)\cdot(-\sin\sqrt x)\cdot\frac{1}{2\sqrt x}=\frac{\sin(\cos\sqrt x)\sin\sqrt x}{2\sqrt x}$.

Revise: Calculus (Class 11 notes)

1. a$1$
2. b$2$
3. c$0$
4. d$-1$

Answer (d): $\frac{d}{dx}(x^2+2x+2)=2x+2=0$ gives $x=-1$.

Revise: Calculus (Class 11 notes)

1. a$-1$
2. b$1$
3. c$6$
4. d$0$

Answer (a): $y''=6x+6=0$ gives $x=-1$, and $y''$ changes sign there.

Revise: Calculus (Class 11 notes)

1. a$\tan\frac x2$
2. b$-\cot\frac x2$
3. c$\cos\frac x2$
4. d$-\tan\frac x2$

Answer (b): $1-\cos x=2\sin^2\frac x2$, so the integral is $\frac12\int\csc^2\frac x2,dx=-\cot\frac x2$.

Revise: Calculus (Class 11 notes)

1. a$\infty$
2. b$\ln|2|$
3. c$0$
4. d$1$

Answer (b): Put $u=1+\sin x$: the integral is $\ln(1+\sin x)\Big|_0^{\pi/2}=\ln2-\ln1=\ln2$.

Revise: Calculus (Class 11 notes)

1. afirst
2. bsecond
3. cthird
4. dfourth

Answer (c): In edu-CA-tion the primary stress falls on the third syllable (-ca-).

Revise: Grammar and Usage (Class 11 notes)

1. aSimple
2. bDifficult
3. ceasy
4. dstrange

Answer (b): Arduous means requiring great effort, so its synonym is difficult.

Revise: Vocabulary and Word Formation (Class 11 notes)

1. aPedantic
2. bimplicit
3. cExplicit
4. dobnoxious

Answer (c): Obscure means unclear or hard to understand; explicit means stated clearly, the best opposite here.

Revise: Vocabulary and Word Formation (Class 11 notes)

1. aChute
2. bchess
3. cchild
4. dcheap

Answer (a): Chef begins with the /sh/ sound, the same as chute. Chess, child and cheap start with /ch/.

Revise: Grammar and Usage (Class 11 notes)

1. aHut/hot
2. bsit/seat
3. csalt/mark
4. dpair/tear

Answer (d): 'Pair' and 'tear' (to rip) share the vowel /eə/. Hut/hot, sit/seat and salt/mark have different vowels.

Revise: Grammar and Usage (Class 11 notes)

1. aFrom: at
2. bfrom: in
3. cfrom: on
4. dto: at

Answer (c): The verb 'differ' takes 'from' for the person and 'on' for the point of disagreement: 'differ from you on this point'.

Revise: Grammar and Usage (Class 11 notes)

1. aTo
2. bwith
3. cabout
4. dfor

Answer (d): The noun 'sympathy' is followed by 'for' when it is directed at a group: 'sympathy for the poor'.

Revise: Grammar and Usage (Class 11 notes)

1. aat
2. bin
3. con
4. dover

Answer (c): The verb insist takes the preposition on.

Revise: Grammar and Usage (Class 11 notes)

1. astrict
2. bsecret
3. cservile
4. dsuspicious

Answer (b): A hole and corner method means done in a secret, underhand way.

Revise: Vocabulary and Word Formation (Class 11 notes)

1. aPungent
2. bedible
3. cpalatable
4. dsensuous

Answer (c): Palatable means pleasant to the taste.

Revise: Vocabulary and Word Formation (Class 11 notes)

1. aun-
2. bmis-
3. cdis-
4. dnone-

Answer (c): Displeased is the correct word formed with the prefix dis-.

Revise: Vocabulary and Word Formation (Class 11 notes)

1. aomnipresent
2. bomniscient
3. ctheist
4. domnipotent

Answer (a): Omnipresent means present everywhere; omniscient means all-knowing and omnipotent means all-powerful.

Revise: Vocabulary and Word Formation (Class 11 notes)

1. aCibphobia
2. bergophobia
3. cPanthophobia
4. dhyctophobia

Answer (a): Cibophobia (cibus, food) is the fear of food. Ergophobia is fear of work.

Revise: Vocabulary and Word Formation (Class 11 notes)

1. aCall
2. bknell
3. creplica
4. dinvitation

Answer (b): A knell is the sound of a bell rung slowly at a funeral.

Revise: Vocabulary and Word Formation (Class 11 notes)

1. aMust buy
2. bmust have bought
3. cmust be buying
4. dmust buying

Answer (c): The time word now and the ongoing trend need a present continuous with a modal of deduction: must be buying.

Revise: Grammar and Usage (Class 11 notes)

1. aAlike
2. blike as
3. clike to
4. dlike

Answer (d): 'Chipmunks are like most other ground squirrels' is a complete, correct predicate. 'Alike' cannot take an object and 'like as'/'like to' are wrong.

Revise: Grammar and Usage (Class 11 notes)

1. ahas been working
2. bworks
3. chad worked
4. dworked

Answer (a): A duration phrase (the whole day long) with an action continuing up to now takes the present perfect continuous.

Revise: Grammar and Usage (Class 11 notes)

1. avery
2. bto
3. cso
4. dextremely

Answer (b): 'Too busy to take care' is the 'too ... to' pattern, meaning so busy that he cannot. 'So' would need 'that'.

Revise: Grammar and Usage (Class 11 notes)

1. aknow
2. bknowing
3. cto know
4. dto be known

Answer (c): 'Demand to know' is the correct construction, an infinitive after demand.

Revise: Grammar and Usage (Class 11 notes)

1. aBut also
2. band
3. calso
4. dbut

Answer (d): 'But' here means 'except': the mail comes every day except Saturday.

Revise: Grammar and Usage (Class 11 notes)

1. athe
2. ba
3. can
4. dsome

Answer (a): Paid by the month is the fixed phrase with the definite article.

Revise: Grammar and Usage (Class 11 notes)

1. aare
2. bis
3. chas
4. dhave

Answer (b): Subjects joined by and but each preceded by every take a singular verb: is.

Revise: Grammar and Usage (Class 11 notes)

1. aSome of rice is still left.
2. bTime and tide wait for none.
3. cShe absents herself from the college today.
4. dNone of the squares was properly drawn.

Answer (d): 'None of the squares was properly drawn' is acceptable. 'Some of rice' needs 'the', and 'wait for none' is not the idiom ('no man').

Revise: Grammar and Usage (Class 11 notes)

1. aHowever, hard she worked, she failed in the exams.
2. bIt rained heavily, however he came to school.
3. cIn spite of heavy rain, he come to school
4. dNeither she nor he will come.

Answer (a): A complex sentence has one main clause and a dependent clause. 'However hard she worked' is a dependent clause, so a is complex.

Revise: Grammar and Usage (Class 11 notes)

1. aSympathize
2. blighten
3. cPerception
4. dmoral

Answer (d): 'Moral' is an adjective. Sympathize and lighten are verbs and perception is a noun.

Revise: Grammar and Usage (Class 11 notes)

1. aMagnetic field
2. belectric field
3. cMagnetic flux
4. delectric flux

Answer (c): $[h]=ML^2T^{-1}$ and $[e]=AT$, so $[h/e]=ML^2T^{-2}A^{-1}$, which is the dimension of magnetic flux (weber).

Revise: Physical Quantities (Class 11 notes)

1. a$5$
2. b$4$
3. c$11$
4. d$2$

Answer (d): Leading zeros do not count; the digits 3 and the trailing 0 are significant, giving 2.

Revise: Physical Quantities (Class 11 notes)

1. a$\mu_s\geq\mu_k$
2. b$\mu_s<\mu_k$
3. c$\mu_s=0$ and $\mu_k>0$
4. d$\mu_s<0$ and $\mu_k<0$

Answer (a): Limiting static friction is at least as large as kinetic friction, so mu_s is greater than or equal to mu_k.

Revise: Dynamics (Class 11 notes)

1. a$0.10$
2. b$0.20$
3. c$0.40$
4. d$0.65$

Answer (d): Poisson's ratio for ordinary materials lies between -1 and 0.5, so 0.65 is impossible.

Revise: Elasticity (Class 11 notes)

1. a$7.348$ cm
2. b$0.918$ cm
3. c$3.674$ cm
4. d$1.837$ cm

Answer (c): Equilibrium needs $h\rho g=\frac{2T}{r}$, so $h=\frac{2(72\times10^{-3})}{0.4\times10^{-3}\times1000\times9.8}=0.03674$ m $=3.674$ cm.

1. a$0.5\%$
2. b$1\%$
3. c$2\%$
4. d$4\%$

Answer (d): Expansion is uniform, so area expansion is twice the linear one: $2\times2%=4%$.

Revise: Thermal Expansion (Class 11 notes)

1. aOne atmosphere
2. bhalf atmosphere
3. cTwo atmosphere
4. d50 atmosphere

Answer (c): A domestic pressure cooker works at roughly twice atmospheric pressure, raising the boiling point to about 120 C.

Revise: Heat and Temperature (Class 11 notes)

1. a$T^4$
2. b$1/T^4$
3. c$1/T$
4. d$T$

Answer (d): $\lambda=\frac{kT}{\sqrt2\pi d^2P}$, so at constant pressure $\lambda\propto T$.

Revise: Ideal Gas (Class 11 notes)

1. a$16.8\%$
2. b$26.81\%$
3. c$36.8\%$
4. d$46.8\%$

Answer (b): $\eta=1-\frac{T_2}{T_1}=1-\frac{273}{373}=0.2681=26.81%$.

Revise: Second Law of Thermodynamics (Class 12 notes)

1. aRefraction
2. binterference
3. cBeats
4. ddiffraction

Answer (d): Bending of waves around corners or obstacles is diffraction.

Revise: Diffraction of Light (Class 12 notes)

1. a$0$
2. b$\pi/4$
3. c$\pi$
4. d$2\pi$

Answer (c): The two prongs move in opposite directions at each instant, so they are out of phase by pi.

Revise: Wave in Pipes and Strings (Class 12 notes)

1. a$\infty$
2. b$f$
3. c$2f$
4. d$f/2$

Answer (d): For a convex mirror $f>0$ with the usual sign rule, $u=-f$: $1/v=1/f+1/f=2/f$, so $v=f/2$ behind the mirror.

Revise: Reflection at Curved Mirrors (Class 11 notes)

1. aBlack
2. bBlue
3. cWhite
4. dRed

Answer (a): The Moon has no atmosphere, so there is no scattering of sunlight and the sky looks black.

Revise: Dispersion (Class 11 notes)

1. aConvergent lens
2. bconcave mirror
3. cDivergent lens
4. dplane mirror

Answer (c): A lens of lower refractive index than its surroundings acts opposite to normal: a convex air bubble in glass is divergent.

Revise: Lenses (Class 11 notes)

1. aReflection only
2. blateral Shift
3. cDispersion and derivation both
4. dDispersion or deviation

Answer (d): Two prisms combined can give dispersion without deviation or deviation without dispersion, depending on the arrangement.

Revise: Refraction Through Prisms (Class 11 notes)

1. aNegative charge
2. bwave nature
3. cSpin
4. dsmall size

Answer (b): The short de Broglie wavelength of fast electrons gives high resolving power.

Revise: Electrons (Class 12 notes)

1. aOn a straight line
2. bOn corners of equilateral triangle
3. cOn three corners of a rectangle
4. dOn the corners of a cube

Answer (a): Three free charges can balance only when collinear, with the middle one of opposite sign and smaller magnitude.

Revise: Electric Charges (Class 11 notes)

1. a6400 MF
2. b6400 F
3. c1 F
4. d711 $\mu$F

Answer (d): $C=4\pi\varepsilon_0R=\frac{6.4\times10^6}{9\times10^9}=7.11\times10^{-4}$ F $=711,\mu$F.

Revise: Capacitor (Class 11 notes)

1. a1:1
2. b1:8
3. c8:1
4. d1:2

Answer (a): Specific resistance is a property of the material, so for the same material the ratio is 1:1.

Revise: DC Circuit (Class 11 notes)

1. azero
2. b$2\mu_0ni$
3. c$\mu_0ni$
4. d$\mu ni$

Answer (c): Inside a long solenoid the field is uniform with $B=\mu_0 n i$.

Revise: Magnetic Field (Class 12 notes)

1. aNuclear forces
2. bCoulomb forces
3. cVan der Waals force
4. dGravitational forces

Answer (b): Electrons are bound to the nucleus by the electrostatic (Coulomb) attraction. Nuclear forces act only between nucleons and gravity is negligible.

Revise: Quantization of Energy (Class 12 notes)

1. aLyman
2. bBracket and Paschen
3. cBalmer
4. dPaschen

Answer (c): The Balmer series (transitions to n=2) lies in the visible region.

Revise: Quantization of Energy (Class 12 notes)

1. a1600 yrs
2. b3200 yrs
3. c800 yrs
4. d2309 yrs

Answer (d): $\tau=\frac{T_{1/2}}{0.693}=\frac{1600}{0.693}\approx2309$ years.

Revise: Radioactivity and Nuclear Reaction (Class 12 notes)

1. aSame for all elements
2. bDifferent for different elements
3. cA universal constant
4. dIs different for lighter elements but same for heavier elements.

Answer (d): The Rydberg constant depends slightly on the nuclear mass through the reduced mass, $R_M=R_\infty/(1+m/M)$. The effect is noticeable for light nuclei and negligible for heavy ones.

Revise: Quantization of Energy (Class 12 notes)

1. a3
2. b4
3. c6
4. d9

Answer (d): The number of orbitals in a shell is $n^2=9$ (1 s, 3 p and 5 d).

Revise: Atomic Structure (Class 11 notes)

1. a18
2. b1
3. c1.8
4. d180

Answer (b): Moles $=\frac{18}{18}=1$ since the molar mass of water is 18 g/mol.

Revise: Stoichiometry (Class 11 notes)

1. a4 minutes
2. b30 minutes
3. c60 minutes
4. d120 minutes

Answer (c): One quarter means two half-lives: 2 x 30 = 60 minutes.

Revise: Nuclear Chemistry (Class 12 notes)

1. a+1
2. b0
3. c-1
4. d+3

Answer (a): H is +1 and O is -2, so Cl is +1 to make the molecule neutral.

Revise: Oxidation and Reduction (Class 11 notes)

1. a2
2. b4
3. c6
4. d8

Answer (b): Mass of Fe per molecule $=0.0033\times67200=221.8$; atoms $=\frac{221.8}{55.85}\approx4$.

Revise: Stoichiometry (Class 11 notes)

1. aBoyle's Law
2. bCharles's Law
3. cGraham's Law
4. dDalton's Law

Answer (a): At constant temperature, pressure and volume of a fixed gas are inversely proportional: Boyle's law.

Revise: States of Matter (Class 11 notes)

1. aA=2, 8,4
2. bB=2,8,8
3. cC=2,8,1
4. dD=2,8,7

Answer (c): C has a single outer electron which it loses most easily, making it the most metallic.

Revise: Classification of Elements (Class 11 notes)

1. a$\ce{C2H6}$
2. b$\ce{H2O}$
3. c$\ce{CH4}$
4. d$\ce{NH3}$

Answer (a): VSEPR gives the shape around a single central atom; ethane has two carbon centres, so no single molecular geometry is assigned.

Revise: Chemical Bonding (Class 11 notes)

1. a3 times
2. b6 times
3. c9 times
4. d27 times

Answer (d): Taking the rate law from the stoichiometry, rate $=k[A]^2[B]$, so tripling both gives $3^3=27$ times.

Revise: Chemical Kinetics (Class 12 notes)

1. aAcidic
2. bBasic
3. cNeutral
4. dNone

Answer (c): NaCl is a salt of a strong acid and strong base, so it does not hydrolyse and the solution is neutral.

Revise: Ionic Equilibrium (Class 12 notes)

1. a7.0
2. b>7.0
3. c<7.0
4. dcannot be predicted

Answer (c): $K_w$ rises with temperature, so $[H^+]>10^{-7}$ and pH falls below 7 while water stays neutral.

Revise: Ionic Equilibrium (Class 12 notes)

1. aZn
2. bMn
3. cCu
4. dPb

Answer (b): Only very active metals such as Mg and Mn release hydrogen with very dilute nitric acid; Zn, Cu and Pb give nitrogen oxides.

Revise: Chemistry of Metals (Class 11 notes)

1. a$1N;H_2SO_4$
2. b$2N;H_2SO_4$
3. c$0.5N;H_2SO_4$
4. d$4N;H_2SO_4$

Answer (b): $N=M\times$ basicity $=1\times2=2N$.

Revise: Volumetric Analysis (Class 12 notes)

1. aOrtho hydrogen
2. bpara hydrogen
3. cheavy hydrogen
4. dnascent hydrogen

Answer (a): Ortho hydrogen has nuclear spins in the same direction; para hydrogen has them opposite.

Revise: Chemistry of Non-Metals (Class 11 notes)

1. aSolvay's process
2. bHaber's process
3. cOstwald's process
4. dDown's process

Answer (b): Haber's process combines $\ce{N2}$ and $\ce{H2}$ over an iron catalyst.

Revise: Modern Chemical Manufactures (Class 11 notes)

1. aFe
2. bCu
3. cZn
4. dHg

Answer (a): Haematite is $\ce{Fe2O3}$, an ore of iron.

Revise: Chemistry of Metals (Class 11 notes)

1. a$\ce{BF3}$
2. b$\ce{NH3}$
3. c$\ce{H2O}$
4. d$\ce{OH-}$

Answer (a): $\ce{BF3}$ has an empty orbital on boron and is an electron acceptor (electrophile); the others have lone pairs.

Revise: Haloalkanes (Class 12 notes)

1. aPropene
2. b1-Butane
3. c2-Butene
4. dPent-2-one

Answer (a): Anti-Markovnikov addition of HBr (peroxide effect) needs an unsymmetrical alkene, and propene is the only one listed; 2-butene is symmetrical, and 1-butane is an alkane, not an alkene.

Revise: Hydrocarbons (Class 11 notes)

1. aChloroform
2. bdiethyl ether
3. cacetone
4. dformic acid

Answer (d): Glycerol with oxalic acid at 110 C gives formic acid (and CO2).

Revise: Carboxylic Acids (Class 12 notes)

1. a$-NH_2$
2. b$-OH$
3. c$-COOH$
4. d-R

Answer (c): Electron-withdrawing groups such as -COOH direct the incoming group to the meta position.

Revise: Aromatic Hydrocarbons (Class 11 notes)

1. a2
2. b3
3. c4
4. d6

Answer (b): Dichlorobenzene exists as ortho, meta and para isomers: 3.

Revise: Aromatic Hydrocarbons (Class 11 notes)

1. aPolyethene
2. bTerylene
3. cPVC
4. dTeflon

Answer (b): Terylene (polyester) forms by condensation of a diacid and a diol with loss of water; the others are addition polymers.

Revise: Modern Chemical Manufactures (Class 11 notes)

1. aAntiseptic drug
2. bAntipyretic drug
3. cAntibiotic drug
4. dAnalgesic drug

Answer (c): Penicillin is an antibiotic.

Revise: Chemistry in the Service to Mankind (Class 12 notes)

1. aCarbohydrates
2. bProtein
3. cLipids
4. dNucleic acids

Answer (b): Enzymes are biological catalysts made of protein.

Revise: Biomolecules (Class 11 notes)

1. aAdenine
2. bGuanine
3. cUracil
4. dCytosine

Answer (c): Uracil replaces thymine in RNA and is absent from DNA.

Revise: Biomolecules (Class 11 notes)