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JEE Main 2021 (24 Feb Shift 2)

2021 · 90 questions · First 10 Solutions Free
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Q1 mcq
In the given figure, a body of mass $M$ is held between two massless springs, on a smooth inclined plane. The free ends of the springs are attached to firm supports. If each spring has spring constant $k,$ the frequency of oscillation of given body is:
Question 1 image
a.
$\frac{1}{2\pi}\sqrt{\frac{2k}{Mgsin\alpha}}$
b.
$\frac{1}{2\pi}\sqrt{\frac{k}{Mg}}sin\alpha$
c.
$\frac{1}{2\pi}\sqrt{\frac{k}{2M}}$
d.
$\frac{1}{2\pi}\sqrt{\frac{2k}{M}}$ Correct Answer

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Q2 mcq
A particle is projected with velocity $v_{0}$ along $x$ -axis. A damping force is acting on the particle which is proportional to the square of the distance from the origin i.e. $ma= -\alpha x^{2}.$ The distance at which the particle stops:
a.
$\frac{1}{3}$ $( \frac{2v_{0}}{3\alpha})$
b.
$\frac{1}{3}$ $( \frac{3mv^{2}_{0}}{2\alpha})$ Correct Answer
c.
$\frac{1}{2}$ $( \frac{3v^{2}_{0}}{2\alpha})$
d.
$\frac{1}{2}$ $( \frac{2v^{2}_{0}}{3\alpha})$

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Q3 mcq
A soft ferromagnetic material is placed in an external magnetic field. The magnetic domains:
a.
have no relation with external magnetic field.
b.
decrease in size and changes orientation.
c.
increase in size but no change in orientation.
d.
may increase or decrease in size and change its orientation. Correct Answer

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Q4 nat
A uniform thin bar of mass $6\, kg$ and length $2. 4$ meter is bent to make an equilateral hexagon. The moment of inertia about an axis passing through the centre of mass and perpendicular to the plane of hexagon is ___________ $\times 10^{-1}\, kg \,m^{2}.$
✓ Accepted Answer: 8

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Q5 nat
An electromagnetic wave of frequency $3\, GHz$ enters a dielectric medium of relative electric permittivity $2. 25$ from vacuum. The wavelength of this wave in that medium will be _________ $\times 10^{-2}\, cm.$
✓ Accepted Answer: 667

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Q6 nat
A uniform metallic wire is elongated by $0. 04\,m$ when subjected to a linear force $F.$ The elongation, if its length and diameter is doubled and subjected to the same force will be _________ $cm.$
✓ Accepted Answer: 2

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Q7 mcq
An X-ray tube is operated at $1. 24$ million volt. The shortest wavelength of the produced photon will be:
a.
$10^{-3} nm$ Correct Answer
b.
$10^{-2} nm$
c.
$10^{-4} nm$
d.
$10^{-1} nm$

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Q8 nat
A point charge of $+12\,\mu C$ is at a distance $6\, cm$ vertically above the centre of a square of side $12\, cm$ as shown in figure. The magnitude of the electric flux through the square will be _______ $\times 10^{3}\,N\,m^{2}\,C^{-1}.$
✓ Accepted Answer: 226

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Q9 mcq
Two electrons each are fixed at a distance $2d.$ A third charge proton placed at the midpoint is displaced slightly by a distance $x(x\ll d)$ perpendicular to the line joining the two fixed charges. Proton will execute simple harmonic motion having angular frequency: ( $m=$ mass of charged particle)
a.
$\frac{1}{2}$ $(\frac{\pi \epsilon _{0}md^{3}}{2q^{2}})$
b.
$\frac{1}{2}$ $( \frac{2\pi \epsilon _{0}md^{3}}{q^{2}})$
c.
$\frac{1}{2}$ $(\frac{q^{2}}{2\pi \epsilon _{0}md^{3}})$ Correct Answer
d.
$\frac{1}{2}$ $( \frac{2q^{2}}{\pi \epsilon _{0}md^{3}})$

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Q10 nat
A signal of $0. 1\, kW$ is transmitted in a cable. The attenuation of cable is $-5\, dB$ per $km$ and cable length is $20\, km.$ The power received at the receiver is $10^{-x}\,W.$ The value of $x$ is _________. [Gain in $dB = 10\, log_{10}(\frac{P_{O}}{P_{i}} )$ ]
✓ Accepted Answer: 8

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Q11 mcq
If the source of light used in a Young's double slit experiment is changed from red to violet:
a.
consecutive fringe lines will come closer.
b.
the fringes will become brighter.
c.
the central bright fringe will become a dark fringe.
d.
the intensity of minima will increase.
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Q12 mcq
If one mole of an ideal gas at $(P_{1},V_{1})$ is allowed to expand reversibly and isothermally ( $A$ to $B$ ) its pressure is reduced to one-half of the original pressure (see figure). This is followed by a constant volume cooling till its pressure is reduced to one-fourth of the initial value $(B\rightarrow \rightarrow C).$ Then it is restored to its initial state by a reversible adiabatic compression ( $C$ to $A$ ). The net workdone by the gas is equal to:
Question 12 image
a.
$0$
b.
$RTln(2)$
c.
$-\frac{RT}{2(\gamma -1)}$
d.
$RT [ln(2) - \frac{1}{2(\gamma -1)}]$
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Q13 nat
Two cars are approaching each other at an equal speed of $7. 2\, km \, hr^{-1}.$ When they see each other, both blow horns having a frequency of $676\, Hz.$ The beat frequency heard by each driver will be _______ $Hz.$ [Velocity of sound in air is $340\,m\,s^{-1}.$
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Q14 nat
The root-mean-square speed of molecules of a given mass of a gas at $27\,^{\circ}C$ and $1$ atmosphere pressure is $200\,m\,s^{-1}.$ The root-mean-square speed of molecules of the gas at $127\,^{\circ}C$ and $2$ atmosphere pressure is $\frac{x}{\sqrt{3}}\,m\,s^{-1}.$ The value of $x$ will be __________.
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Q15 mcq
The de Broglie wavelength of a proton and -particle are equal. The ratio of their velocities is$\alpha$
a.
$4 : 1$
b.
$4 : 3$
c.
$1 : 4$
d.
$4 : 2$
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Q16 mcq
Given below are two statements: Statement I: $p- n$ junction diodes can be used to function as a transistor, simply by connecting two diodes, back to back, which acts as the base terminal Statement II: In the study of transistors, the amplification factor $\beta$ indicates ratio of the collector current to the base current. In the light of the above statements, choose the correct answer from the options given below.
a.
Both Statement I and Statement II are false
b.
Statement I is true but Statement II is false
c.
Statement I is false but Statement II is true
d.
Both Statement I and Statement II are true
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Q17 mcq
Which of the following equations represents a travelling wave?
a.
$y=Asin(15x-2t)$
b.
$y=Ae^{x} cos(\omega t- \theta )$
c.
$y= Ae^{-x^{2}}(vt+\theta )$
d.
$y=Asinx\, cos\omega t$
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Q18 mcq
A body weighs $49\,N$ on a spring balance at the north pole. What will be its weight recorded on the same weighing machine, if it is shifted to the equator? [Use $g= \frac{GM}{R^{2}} = 9. 8\,m\,s^{-2}$ and radius of earth, $R= 6400\, km.$ ]
a.
$49. 17\,N$
b.
$48. 83\,N$
c.
$49. 83\,N$
d.
$49\,N$
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Q19 nat
A cylindrical wire of radius $0. 5\, mm$ and conductivity $5 \times 10^{7}\,S\,m^{-1}$ is subjected to an electric field of $10\, mV \,m^{-1}.$ The expected value of current in the wire will be $x^{3}\pi \, mA.$ The value of $x$ is _________.
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Q20 mcq
When a particle executes SHM, the nature of graphical representation of velocity as a function of displacement is:
a.
straight line
b.
elliptical
c.
circular
d.
parabolic
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Q21 mcq
On the basis of kinetic theory of gases, the gas exerts pressure because its molecules:
a.
continuously stick to the walls of container.
b.
suffer change in momentum when impinge on the walls of container.
c.
continuously lose their energy till it reaches wall.
d.
are attracted by the walls of container.
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Q22 mcq
The period of oscillation of a simple pendulum is $T = 2\pi \sqrt{\frac{L}{g}}.$ Measured value of $L$ is $1. 0\,m$ from meter scale having a minimum division of $1\, mm$ and time of one complete oscillation is $1. 95\,s$ measured from stopwatch of $0. 01\,s$ resolution. The percentage error in the determination of $'g'$ will be:
a.
$1. 03%$
b.
$1. 33%$
c.
$1. 30%$
d.
$1. 13%$
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Q23 mcq
Zener breakdown occurs in a $p- n$ junction having $p$ and $n$ both:
a.
lightly doped and have narrow depletion layer.
b.
heavily doped and have wide depletion layer.
c.
lightly doped and have wide depletion layer.
d.
heavily doped and have narrow depletion layer.
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Q24 mcq
The figure shows a circuit that contains four identical resistors with resistance $R= 2. 0\,\Omega ,$ two identical inductors with inductance $L= 2. 0\, mH$ and an ideal battery with E.M.F. $E = 9\,V.$ The current $i$ just after the switch $S$ is closed will be:
a.
$9\,A$
b.
$3. 37\,A$
c.
$2. 25\,A$
d.
$3. 0\,A$
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Q25 mcq
Match List - I with List - II. List-I List-II (a) Source of microwave frequency (i) Radioactive decay of nucleus (b) Source of infrared frequency (ii) Magnetron (c) Source of Gamma Rays (iii) Inner shell electrons (d) Source of $X$ -rays (iv) Vibration of atoms and molecules (v) LASER (vi) RC circuit Choose the correct answer from the options given below:
a.
(a)-(ii), (b)-(iv), (c)-(vi), (d)-(iii)
b.
(a)-(vi), (b)-(iv), (c)-(i), (d)-(v)
c.
(a)-(vi), (b)-(v), (c)-(i), (d)-(iv)
d.
(a)-(ii), (b)-(iv), (c)-(i), (d)-(iii)
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Q26 mcq
The logic circuit shown above is equivalent to :
Question 26 image
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Q27 nat
A series LCR circuit is designed to resonate at an angular frequency $\omega _{0} = 10^{5}\, rad \,s^{-1}.$ The circuit draws $16\,W$ power from $120\,V$ source at resonance. The value of resistance $R$ in the circuit is ________ $\Omega .$
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Q28 mcq
A circular hole of radius $(\frac{a}{2})$ is cut out of a circular disc of radius $a$ as shown in figure. The centroid of the remaining circular portion with respect to point $O$ will be:
Question 28 image
a.
$\frac{2}{3}a$
b.
$\frac{5}{6}a$
c.
$\frac{1}{6}a$
d.
$\frac{10}{11} a$
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Q29 nat
Two solids $A$ and $B$ of mass $1\, kg$ and $2\, kg$ respectively are moving with equal linear momentum. The ratio of their kinetic energies $(K.E. )_{A} : (K.E. )_{B}$ will be $\frac{A}{1},$ so the value of $A$ will be _________.
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Q30 mcq
According to Bohr atom model, in which of the following transitions will the frequency be maximum?
a.
$n= 3$ to $n= 2$
b.
$n= 5$ to $n= 4$
c.
$n= 4$ to $n= 3$
d.
$n= 2$ to $n= 1$
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Q31 nat
Assuming ideal behaviour, the magnitude of $log \,K$ for the following reaction at $25^{\circ}C$ is $x \times 10^{-1}.$ The value of $x$ is __________. (Integer answer) $3HC \equiv CH_{(g)} \rightleftharpoons C_{6}H_{6(l)}$ [Given: $\Delta _{f}G^{\circ}(HC \equiv CH) = -2. 04 \times 10^{5}\,J\, mol^{-1}; \,\Delta _{f}G^{\circ}(C_{6}H_{6}) = -1. 24 \times 10^{5}\,J\, mol^{-1}; \,R = 8. 314\,J\,K^{-1}\, mol^{-1}$ ]
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Q32 nat
Sucrose hydrolyses in acid solution into glucose and fructose following first order rate law with a half-life of $3. 33\,h$ at $25^{\circ}C.$ After $9\,h,$ the fraction of sucrose remaining is $f.$ The value of $log_{10}(\frac{1}{f})$ is ________ $\times 10^{-2}.$ (Rounded off to the nearest integer) [Assume: In $10 = 2. 303, \, ln \,2 = 0. 693$ ]
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Q33 mcq
In polymer Buna- $S :'S'$ stands for:
a.
Strength
b.
Sulphur
c.
Sulphonation
d.
Styrene
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Q34 nat
The solubility product of $PbI_{2}$ is $8. 0 \times 10^{-9}.$ The solubility of lead iodide in $0. 1$ molar solution of lead nitrate is $x\times 10^{-6}\, mol /L.$ The value of $x$ is _________ (Rounded off to the nearest integer) [Given $\sqrt{2}= 1. 41$ ]
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Q35 mcq
The incorrect statement among the following is:
a.
$Cr_{2}O_{3}$ is an amphoteric oxide
b.
$VOSO_{4}$ is a reducing agent
c.
$RuO_{4}$ is an oxidizing agent
d.
Red colour of ruby is due to the presence of $Co^{3+}$
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Q36 mcq
What is the correct order of the following elements with respect to their density?
a.
$Zn < Cu < Co < Fe < Cr$
b.
$Cr < Zn < Co < Cu < Fe$
c.
$Zn < Cr < Fe < Co < Cu$
d.
$Cr < Fe < Co < Cu < Zn$
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Q37 mcq
The diazonium salt of which of the following compounds will form a coloured dye on reaction with $\beta$ - Naphthol in $NaOH?$
Question 37 image
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Q38 nat
$1. 86\,g$ of aniline completely reacts to form acetanilide. $10%$ of the product is lost during purification. Amount of acetanilide obtained after purification (in $g$ ) is ___________ $\times 10^{-2}.$
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Q39 nat
The formula of a gaseous hydrocarbon which requires 6 times of its own volume of $O_{2}$ for complete oxidation and produces $4$ times its own volume of $CO_{2}$ is $C_{x}H_{y}.$ The value of $y$ is ________.
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Q40 nat
The magnitude of the change in oxidising power of the $MnO^{-}_{4} / Mn^{2+}$ couple is $x \times 10^{-4}\,V$ if the $H^{+}$ concentration is decreased from $1\,M$ to $10^{-4}M$ at $25^{\circ}C.$ (Assume concentration of $MnO^{-}_{4}$ and $Mn^{2+}$ to be same on change in $H^{+}$ concentration). The value of $x$ is __________. (Rounded off to the nearest integer) [Given: $\frac{2.303 RT}{F} = 0. 059$ ]
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Q41 mcq
The correct order of the following compounds showing increasing tendency towards nucleophilic substitution reaction is:
Question 41 image
a.
(iv) < (i) < (ii) < (iii)
b.
(i) < (ii) < (iii) < (iv)
c.
(iv) < (i) < (iii) < (ii)
d.
(iv) < (iii) < (ii) < (i)
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Q42 mcq
Which one of the following carbonyl compounds cannot be prepared by addition of water on an alkyne in the presence of $HgSO_{4}$ and $H_{2}SO_{4}?$
Question 42 image
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Q43 mcq
Match List - I with List - II. List-I List-II (a) Valium (i) Antifertility drug (b) Morphine (ii) Pernicious anaemia (c) Norethindrone (iii) Analgesic (d) Vitamin $B_{12}$ (iv) Tranquilizer
a.
(a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)
b.
(a)-(ii), (b)-(iv), (c)-(iii), (d)-(i)
c.
(a)-(i), (b)-(iii), (c)-(iv), (d)-(ii)
d.
(a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)
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Q44 mcq
What is the correct sequence of reagents used for converting nitrobenzene into $m$ -dibromobenzene?
Question 44 image
a.
$^{Sn / HCl}\rightarrow \rightarrow /^{KBr} /^{Br_{2}} /^{H}\rightarrow \rightarrow^{+}$
b.
$------^{Br_{2}/ Fe} /^{Sn / HCl}\rightarrow \rightarrow /^{NaNO_{2}/ HCl} /^{CuBr / HBr}\rightarrow \rightarrow$
c.
$^{NaNO}\rightarrow \rightarrow^{2} /^{HC}\rightarrow \rightarrow^{\vec{l}} /^{K}\rightarrow \rightarrow^{\vec{B}r} /^{H}\rightarrow \rightarrow^{+}$
d.
$------^{Sn / H}_{\rightarrow \rightarrow }^{\vec{C}l} /^{Br}\rightarrow /\rightarrow^{2}^{NaNO}_{\rightarrow \rightarrow }^{2} /^{NaB}_{\rightarrow \rightarrow }^{\vec{r}}$
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Q45 mcq
Match List - I with List - II. List-I (Salt) List-II (Flame colour wavelength) (a) (i) $Br_{2}/ NaOH$ (b) (ii) $H_{2}/Pd -BaSO_{4}$ (c) (iii) $Zn(Hg)/ Conc. HCl$ (d) (iv) $Cl_{2}/ Red \,P, \,H_{2}O$ Choose the correct answer from the options given below:
Question 45 image
a.
(a)-(ii), (b)-(iv), (c)-(i), (d)-(iii)
b.
(a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)
c.
(a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
d.
(a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)
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Q46 mcq
Which of the following reagent is suitable for the preparation of the product in the above reaction?
a.
Red $P + Cl_{2}$
b.
$NaBH_{4}$
c.
$⊝ \oplus$ $NH_{2}-NH_{2}/C_{2}H_{5}ONa$
d.
$Ni /H_{2}$
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Q47 mcq
Given below are two statements: Statement I: The value of the parameter "Biochemical Oxygen Demand (BOD)" is important for survival of aquatic life. Statement II: The optimum value of BOD is $6. 5\, ppm.$ In the light of the above statements, choose the most appropriate answer from the options given below:
a.
Statement I is true but Statement II is false
b.
Statement I is false but Statement II is true
c.
Both Statement I and Statement II are false
d.
Both Statement I and Statement II are true
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Q48 nat
$C_{6}H_{6}$ freezes at $5. 5^{\circ}C.$ The temperature at which a solution of $10\,g$ of $C_{4}H_{10}$ in $200\,g$ of $C_{6}H_{6}$ freeze is _______ $^{\circ }C.$ (nearest integer value), (The molal freezing point depression constant of $C_{6}H_{6}$ is $5. 12^{\circ}C/m.$ )
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Q49 mcq
Which one of the following compounds is non-aromatic?
Question 49 image
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Q50 mcq
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R. Assertion A: Hydrogen is the most abundant element in the Universe, but it is not the most abundant gas in the troposphere. Reason R: Hydrogen is the lightest element. In the light of the above statements, choose the correct answer from the options given below:
a.
Both A and R are true but R is NOT the correct explanation of A
b.
Both A and R are true and R is the correct explanation of A
c.
A is true but R is false
d.
A is false but R true
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Q51 mcq
The calculated magnetic moments (spin only value) for species $[FeCl_{4}]^{2-}, [Co (C_{2}O_{4})_{3}]^{3-}$ and $MnO^{2-}_{4}$ respectively are:
a.
$4. 90, \,0$ and $1. 73\, BM$
b.
$4. 90, \,0$ and $2. 83\, BM$
c.
$5. 82, \,0$ and $0\, BM$
d.
$5. 92, \,4. 90$ and $0\, BM$
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Q52 mcq
The correct shape and $I -I -I$ bond angles respectively in $I^{-}_{3}$ ion are:
a.
T-shaped; $180^{\circ}$ and $90^{\circ}$
b.
Distorted trigonal planar; $135^{\circ}$ and $90^{\circ}$
c.
Trigonal planar; $120^{\circ}$
d.
Linear; $180^{\circ}$
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Q53 mcq
Most suitable salt which can be used for efficient clotting of blood will be?
a.
$FeCl_{3}$
b.
$Mg (HCO_{3})_{2}$
c.
$FeSO_{4}$
d.
$NaHCO_{3}$
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Q54 mcq
Match List - I with List - II. List-I (Metal) List-II (Ores) (a) Aluminium (i) Siderite (b) Iron (ii) Calamine (c) Copper (iii) Kaolinite (d) Zinc (iv) Malachite Choose the correct answer from the options given below:
a.
(a)-(ii), (b)-(iv), (c)-(i), (d)-(iii)
b.
(a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)
c.
(a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
d.
(a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)
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Q55 nat
The volume occupied by $4. 75\,g$ of acetylene gas at $50^{\circ}C$ and $740\, mm \, Hg$ pressure is ____________ $L.$ (Rounded off to the nearest integer) [Given $R = 0. 0826\,L\, atm \,K^{-1}\, mol^{-1}$ ]
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Q56 mcq
The correct set from the following in which both pairs are in correct order of melting point is:
a.
$LiF > LiCl; NaCl > MgO$
b.
$LiCl > LiF; MgO > NaCl$
c.
$LiCl > LiF; NaCl > MgO$
d.
$LiF > LiCl; MgO > NaCl$
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Q57 mcq
According to Bohr's atomic theory: (A) Kinetic energy of electron is $\propto \frac{Z^{2}}{n^{2}}.$ (B) The product of velocity (v) of electron and principal quantum number $(n), \,'vn'\propto Z^{2}.$ (C) Frequency of revolution of electron in an orbit is $\propto \frac{Z^{3}}{n^{3}}.$ (D) Coulombic force of attraction on the electron is $\propto \frac{Z^{3}}{n^{4}}.$ Choose the most appropriate answer from the options given below:
a.
(A), (C) and (D) only
b.
(A) and (D) only
c.
(C) only
d.
(A) only
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Q58 nat
Among the following allotropic forms of sulphur, the number of allotropic forms, which will show paramagnetism is _______. (A) -sulphur$\alpha$ (B) -sulphur$\beta$ (C) $S_{2}$ -form
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Q59 nat
The total number of amines among the following which can be synthesized by Gabriel synthesis is ________.
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Q60 mcq
Match List - I with List - II. List-I (Salt) List-II (Flame colour wavelength) (a) $LiCl$ (i) $455. 5\, nm$ (b) $NaCl$ (ii) $670. 8\, nm$ (c) $RbCl$ (iii) $780. 0\, nm$ (d) $CsCl$ (iv) $589. 2\, nm$ Choose the correct answer from the options given below:
a.
(a)-(iv), (b)-(ii), (c)-(iii), (d)-(i)
b.
(a)-(i), (b)-(iv), (c)-(ii), (d)-(iii)
c.
(a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
d.
(a)-(ii), (b)-(iv), (c)-(iii), (d)-(i)
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Q61 mcq
Let $a,b\in R.$ If the mirror image of the point $P(a, 6, 9)$ with respect to the line $\frac{x-3}{7} = \frac{y-2}{5} = \frac{z-1}{-9}$ is $(20, \,b, -a-9),$ then $|a+b|$ is equal to:
a.
$86$
b.
$90$
c.
$84$
d.
$88$
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Q62 mcq
If $P$ is a point on the parabola $y=x^{2} + 4$ which is closest to the straight line $y= 4x-1,$ then the co- ordinates of $P$ are:
a.
$(-2, 8)$
b.
$(1, 5)$
c.
$(2, 8)$
d.
$(3, 13)$
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Q63 nat
The students $S_{1},S_{2}, … ,S_{10}$ are to be divided into $3$ groups $A, \,B$ and $C$ such that each group has at least one student and the group $C$ has at most $3$ students. Then the total number of possibilities of forming such groups is __________.
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Q64 mcq
$| |$ Let $f$ be a twice differentiable function defined on $R$ such that $f(0) = 1, \,f'(0) = 2$ and $f'(x) \neq 0$ for all $f(x) f'(x)$ $x\in R.$ If $= 0,$ for all $x\in R,$ then the value of $f(1)$ lies in the interval $f'(x) f''(x)$
a.
$(9, 12)$
b.
$(3, 6)$
c.
$(0, 3)$
d.
$(6, 9)$
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Q65 nat
$21 21$ Let $i= .\sqrt{-1}$ If $\frac{(-1+i\sqrt{3})}{(1-i)^{24}} + \frac{(1+i\sqrt{3})}{(1+i)^{24}} =k,$ and $n= [|k|]$ be the greatest integral part of $|k|.$ Then $\sum ^{n}_{j=0}^{+5} (j+ 5)^{2}- \sum ^{n}_{j=0}^{+5}(j+ 5)$ is equal to ________.
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Q66 nat
The sum of first four terms of a geometric progression $(G. P. )$ is $\frac{65}{12}$ and the sum of their respective reciprocals is $\frac{65}{18}.$ If the product of first three terms of the $G. P.$ is $1,$ and the third term is $\alpha ,$ then $2\alpha$ is _________.
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Q67 mcq
For which of the following curves, the line $x+ \sqrt{3}y= 2\sqrt{3}$ is the tangent at the point $( \frac{3\sqrt{3}}{2}, \frac{1}{2})?$
a.
$2x^{2} -18y^{2} = 9$
b.
$y^{2} = \frac{1}{6\sqrt{3}}x$
c.
$x^{2} + 9y^{2} = 9$
d.
$x^{2} +y^{2} = 7$
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Q68 mcq
The area of the region: $R={(x,y) : 5x^{2} \leq y\leq 2x^{2} + 9}$ is
a.
$9\sqrt{3}$ square units
b.
$12\sqrt{3}$ square units
c.
$11\sqrt{3}$ square units
d.
$6\sqrt{3}$ square units
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Q69 mcq
If a curve $y=f(x)$ passes through the point $(1, \,2)$ and satisfies $x\frac{dy}{dx} +y=bx^{4},$ then for what value of $b,\int _{1}^{2} f(x)dx= \frac{62}{5}?$
a.
$\frac{31}{5}$
b.
$10$
c.
$5$
d.
$\frac{62}{5}$
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Q70 mcq
The negation of the statement $~p\wedge (p\vee q)$ is:
a.
$~p\vee q$
b.
$~p\wedge q$
c.
$p\vee ~q$
d.
$p\wedge ~q$
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Q71 mcq
Let $f :R\rightarrow \rightarrow R$ be defined as $\{-55x, if \,x< -5$ $f(x) =2x^{3} -3x^{2} -120x, if -5 \leq x\leq 4$ $\{_{3}_{2}$ $2x -3x -36x-336, if \,x> 4$ Let $A= {x\in R:f$ is increasing}. Then $A$ is equal to:
a.
$(-5, \infty )$
b.
$(-5, \, -4) \cup (4, \,\infty )$
c.
$(-\infty , -5) \cup (-4, \infty )$
d.
$(-\infty , -5) \cup (4, \infty )$
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Q72 mcq
A possible value of $tan(\frac{1}{4}sin^{-1} \frac{\sqrt{63}}{8})$ is:
a.
$2\sqrt{2}-1$
b.
$\frac{1}{2\sqrt{2}}$
c.
$\sqrt{7}-1$
d.
$\frac{1}{\sqrt{7}}$
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Q73 mcq
Let $A$ and $B$ be $3 \times 3$ real matrices such that $A$ is a symmetric matrix and $B$ is a skew-symmetric matrix. Then the system of linear equations $(A^{2} B^{2} - B^{2} A^{2})X =O,$ where $X$ is a $3 \times 1$ column matrix of unknown variables and $O$ is a $3 \times 1$ null matrix, has
a.
exactly two solutions
b.
infinitely many solutions
c.
a unique solution
d.
no solution
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Q74 mcq
If the curve $y=ax^{2} +bx+c,x\in R,$ passes through the point $(1, \,2)$ and the tangent line to this curve at origin is $y=x,$ then the possible values of $a, \,b, \,c$ are:
a.
$a= -1, \,b= 1, \,c= 1$
b.
$a= 1, \,b= 0, \,c= 1$
c.
$a= 1, \,b= 1, \,c= 0$
d.
$a= \frac{1}{2},b= \frac{1}{2},c= 1$
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Q75 mcq
The value of the integral, $\int _{1}^{3}[x^{2}-2x-2]dx,$ where $[x]$ denotes the greatest integer less than or equal to $x,$ is
a.
$-4$
b.
$-5$
c.
$-\sqrt{2}- \sqrt{3}+ 1$
d.
$-\sqrt{2}- \sqrt{3}-1$
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Q76 mcq
Let $a,b,c$ be in arithmetic progression. Let the centroid of the triangle with vertices $(a,c), (2,b)$ and $(a,b)$ be $(\frac{10}{3}, \frac{7}{3} ).$ If $\alpha ,\beta$ are the roots of the equation $ax^{2} +bx+ 1 = 0,$ then the value of $\alpha ^{2} +\beta ^{2} - \alpha \beta$ is:
a.
$- \frac{71}{256}$
b.
$\frac{69}{256}$
c.
$\frac{71}{256}$
d.
$-\frac{69}{256}$
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Q77 mcq
If $n⩾ 2$ is a positive integer, then the sum of the series $^{n+1}C_{2}+ 2(^{2}C_{2}+^{3}C_{2}+^{4}C_{2}+ … +^{n}C_{2})$ is
a.
$\frac{n(n-1)(2n+1)}{6}$
b.
$\frac{n(n+1)(2n+1)}{6}$
c.
$\frac{n(n+1)^{2}(n+2)}{12}$
d.
$\frac{n(2n+1)(3n+1)}{6}$
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Q78 nat
Let $\lambda$ be an integer. If the shortest distance between the lines $x- \lambda = 2y-1 = -2z$ and $x=y+ 2\lambda =z- \lambda$ is $\frac{\sqrt{7}}{2\sqrt{2}},$ then the value of $|\lambda |$ is _______.
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Q79 nat
Let a point $P$ be such that its distance from the point $(5, 0)$ is thrice the distance of $P$ from the point $(-5, 0).$ If the locus of the point $P$ is a circle of radius $r,$ then $4r^{2}$ (in the nearest integer) is equal to __________.
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Q80 mcq
The angle of elevation of a jet plane from a point $A$ on the ground is $60^{\circ}.$ After a flight of $20$ seconds at the speed of $432\, km / hour$ , the angle of elevation changes to $30^{\circ}.$ If the jet plane is flying at a constant height, then its height is:
a.
$1200\sqrt{3}\,m$
b.
$2400\sqrt{3}\,m$
c.
$1800\sqrt{3}\,m$
d.
$3600\sqrt{3}\,m$
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Q81 nat
$||$ $n^{n}C_{r}, if \,n\geq r\geq 0$ For integers $n$ and $r,$ let $( )={$ . The maximum value of $k$ for which the sum $r 0, otherwise$ $_{k} 10 15_{k+1} 12 13$ $\sum ( )( )+\sum ( )( )$ is maximum, is equal to _________. $^{i=0} i k- i^{i=0} i k+ 1 - i$
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Q82 nat
If the area of the triangle formed by the $x$ -axis, the normal and the tangent to the circle $(x-2)^{2} + (y-3)^{2} = 25$ at the point $(5, 7)$ is $A,$ then $24A$ is equal to _________.
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Q83 nat
If $a+\alpha = 1,b+\beta = 2$ and $af(x) +\alpha f(\frac{1}{x} )=bx+ \frac{\beta}{x},x\neq 0,$ then the value of the expression $\frac{f(x)+f()}{x+^{1}}\frac{1}{x}$ is $x$ ___________.
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Q84 mcq
Let $f(x)$ be a differentiable function defined on $[0, \,2]$ such that $f'(x) =f'(2 - x)$ for all $x\in (0, 2),f(0) = 1$ and $f(2) =e^{2}.$ Then the value of $\int _{0}^{2} f(x)dx$ is
a.
$2(1 +e^{2})$
b.
$1 +e^{2}$
c.
$1 - e^{2}$
d.
$2(1 - e^{2})$
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Q85 nat
The number of the real roots of the equation $(x+ 1)^{2} + x-5 = \frac{27}{4}$ is ________.
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Q86 mcq
The vector equation of the plane passing through the intersection of the planes $\vec{r}\cdot (ˆi +ˆj +ˆk)= 1$ and $\vec{r}\cdot (ˆi -2ˆj)= -2,$ and the point $(1, \,0, \,2)$ is:
a.
$\vec{r}\cdot (ˆi + 7ˆj + 3ˆk)= 7$
b.
$\vec{r}\cdot (ˆi -7ˆj + 3ˆk)= \frac{7}{3}$
c.
$\vec{r}\cdot (ˆi + 7ˆj + 3ˆk)= \frac{7}{3}$
d.
$\vec{r}\cdot (3ˆi + 7ˆj + 3ˆk)= 7$
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Q87 nat
If the variance of $10$ natural numbers $1, \,1, \,1, \, … , \,1, \,k$ is less than $10,$ then the maximum possible value of $k$ is ___________.
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Q88 mcq
For the statements $p$ and $q,$ consider the following compound statements: $(a)\,(~q\wedge (p\rightarrow \rightarrow q)) \rightarrow ~\rightarrow p$ $(b)\,((p\vee q) \wedge ~p) \rightarrow \rightarrow q$ Then which of the following statements is correct?
a.
$(b)$ is a tautology but not $(a)$ .
b.
$(a)$ and $(b)$ both are tautologies.
c.
$(a)$ and $(b)$ both are not tautologies.
d.
$(a)$ is a tautology but not $(b)$ .
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Q89 mcq
For the system of linear equations: $x-2y= 1, \,x- y+kz= -2, \,ky+ 4z= 6, \,k\in R$ Consider the following statements: (A) The system has unique solution if $k\neq 2,k\neq -2.$ (B) The system has unique solution if $k= -2.$ (C) The system has unique solution if $k= 2.$ (D) The system has no-solution if $k= 2.$ (E) The system has infinite number of solutions if $k\neq -2.$ Which of the following statements are correct?
a.
$(A)$ and $(E)$ only
b.
$(B)$ and $(E)$ only
c.
$(A)$ and $(D)$ only
d.
$(C)$ and $(D)$ only
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Q90 mcq
The probability that two randomly selected subsets of the set ${1, 2, 3, 4, 5}$ have exactly two elements in their intersection, is:
a.
$\frac{65}{2^{8}}$
b.
$\frac{65}{2^{7}}$
c.
$\frac{35}{2^{7}}$
d.
$\frac{135}{2^{9}}$
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