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Recent questions and answers in 2018
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JEEMAIN and NEET
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JEEMAIN PAST PAPERS
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2018
A bag contains 4 red and 6 black balls. A ball is drawn at random from the bag, its colour is observed and this ball along with two additional balls of the same colour are returned to the bag. If now a ball is drawn at random from the bag, then the probability that this drawn ball is red, is
jeemain
math
past papers
2018
39
answered
Jul 6, 2019
by
gaja9777
1
answer
PQR is a triangular park with PQ = PR = 200 m. A. T. V. tower stands at the mid-point of QR. If the angles of elevation of the top of the tower at P, Q and R are respectively $45^{\circ},\; 30^{\circ}$ and $30^{\circ}$, then the height of the tower (in m) is :
jeemain
math
past papers
2018
57
answered
May 23, 2019
by
ganeshbaruah0
1
answer
For 1 molal aqueous solution of the following compounds, which one will show the highest freezing point ?
jeemain
chemistry
past papers
2018
89
answered
Mar 20, 2019
by
sharmanamamish9636
1
answer
According to molecular orbital theory, which of the following will not be a viable molecule ?
jeemain
chemistry
past papers
2018
90
asked
Dec 11, 2018
by
pady_1
0
answers
Which of the following compounds contain(s) no covalent bond(s) ? <br> $KCl, \; PH_3,\; O_2, \; B_2H_6, \;H_2SO_4$
jeemain
chemistry
past papers
2018
88
asked
Dec 11, 2018
by
pady_1
0
answers
Which of the following are Lewis acids?
jeemain
chemistry
past papers
2018
87
asked
Dec 11, 2018
by
pady_1
0
answers
The combustion of benzene $(l)$ gives $CO_2(g)$ and $H_2O (l)$. Given that heat of combustion of benzene at constant volume is $-3263.9 \; kJ\; mol^{-1}$ at $25^{\circ}C$; heat of combustion (in $kJ\; mol^{-1}$) of benzene at constant pressure will be - $(R = 8.314 \;JK^{-1} mol^{-1})$
jeemain
chemistry
past papers
2018
86
asked
Dec 11, 2018
by
pady_1
0
answers
Which type of 'defect' has the presence of cations in the interstitial sites ?
jeemain
chemistry
past papers
2018
85
asked
Dec 11, 2018
by
pady_1
0
answers
The oxidation states of $Cr$ in $[Cr(H_2O)_6]Cl_3, [Cr(C_6H_6)_2]$, and $K_2[Cr(CN)_2(O)_2(O_2)(NH_3)]$ respectively are :
jeemain
chemistry
past papers
2018
84
asked
Dec 11, 2018
by
pady_1
0
answers
The predominant form of histamine present in human blood is ($pK_a$ , Histidine = 6.0)
jeemain
chemistry
past papers
2018
83
asked
Dec 11, 2018
by
pady_1
0
answers
The compound that does not produce nitrogen gas by the thermal decomposition is :
jeemain
chemistry
past papers
2018
82
asked
Dec 11, 2018
by
pady_1
0
answers
The recommended concentration of fluoride ion in drinking water is up to 1 ppm as fluoride ion is required to made teeth enamel harder by converting $ [3Ca_3(PO_4)_2.Ca(OH)_2]$ to:
jeemain
chemistry
past papers
2018
81
asked
Dec 11, 2018
by
pady_1
0
answers
An aqueous solution contains $0.10\; M \;H_2S$ and $0.20\; M \; HCl$. If the equilibrium constant for the formation of $HS^-$ from $H_2S$ is $1.0 \times 10^{-7}$ and that of $S^{2-}$ from $HS^-$ ions is $1.2 \times 10^{-13}$ then the concentration of $S^{2-}$ ions in aqueous solution is :
jeemain
chemistry
past papers
2018
80
asked
Dec 11, 2018
by
pady_1
0
answers
When metal 'M' is treated with NaOH, a white gelatinous precipitate 'X' is obtained, which is soluble in excess of NaOH. Compound 'X' when heated strongly gives an oxide which is used in chromatography as an adsorbent. The metal M is :
jeemain
chemistry
past papers
2018
79
asked
Dec 11, 2018
by
pady_1
0
answers
Which of the following compounds will be suitable for Kjeldahl's method for nitrogen estimation ?
jeemain
chemistry
past papers
2018
78
asked
Dec 11, 2018
by
pady_1
0
answers
An aqueous solution contains an unknown concentration of $Ba^{2+}$. When $50\; mL$ of the $1M$ solution of $Na_2SO_4$ is added, $BaSO_4$ just begins to precipitate. The final volume is $500\; mL$. The solubility product of $BaSO_4$ is $1 \times 10^{-10}$. What is the original concentration of $Ba^{2+}$.
jeemain
chemistry
past papers
2018
77
asked
Dec 11, 2018
by
pady_1
0
answers
Phenol on treatment with $CO_2$ in the presence of $NaOH$ followed by acidification produces a compound $X$ as the major product. $X$ on treatment with $(CH_3 CO_2)O$ in presence of catalytic amount of $H_2SO_4$ produced :
jeemain
chemistry
past papers
2018
76
asked
Dec 11, 2018
by
pady_1
0
answers
The major product of the following reaction is : <br>
jeemain
chemistry
past papers
2018
75
asked
Dec 11, 2018
by
pady_1
0
answers
Consider the following reaction and statements : <br> $[Co(NH_3)_4Br_2]^+ + Br^- \to [Co(NH_3)_3Br_3] + NH_3$ <br> (i) Two isomers are produced if the reactant complex ion is a cis-isomer. <br> (ii) Two isomers are produced if the reactant complex ions is a trans-isomer. <br> (iii) Only one isomer is produced if the reactant complex ion is a trans-isomer. <br> (iv) Only one isomer is produced if the reactant complex ion is a cis-isomer. <br> The correct statements are :
jeemain
chemistry
past papers
2018
74
asked
Dec 11, 2018
by
pady_1
0
answers
Glucose on prolonged heating with $HI$ gives :
jeemain
chemistry
past papers
2018
73
asked
Dec 11, 2018
by
pady_1
0
answers
At $518^{\circ}C$, the rate of decomposition of a sample of gaseous acetaldehyde, initially at a pressure of $363 $ Torr, was $1.00 \; Torr\;s^{-1}$ when $5\%$ had reacted and $0.5\; Torr\; s^{-1}$ when $33\%$ had reacted. The order of the reaction is :
jeemain
chemistry
past papers
2018
72
asked
Dec 11, 2018
by
pady_1
0
answers
Which of the following lines correctly show the temperature dependence of equilibrium constant $K$, for an exothermic reaction ? <br>
jeemain
chemistry
past papers
2018
71
asked
Dec 11, 2018
by
pady_1
0
answers
How long (approximate) should water be electrolysed by passing through 100 amperes current so that the oxygen released can completely burn 27.66 g of diborane ? <br> (Atomic weight of B = 10.8 u)
jeemain
chemistry
past papers
2018
70
asked
Dec 11, 2018
by
pady_1
0
answers
The major product formed in the following reaction is : <br>
jeemain
chemistry
past papers
2018
69
asked
Dec 11, 2018
by
pady_1
0
answers
Hydrogen peroxide oxidises $[Fe(CN)_6]^{4-}$ to $[Fe(CN)_6]^{3-}$ in acidic medium but reduces $[Fe(CN)_6]^{3-}$ to $[Fe(CN)_6]^{4-}$ in alkaline medium. The other products formed are, respectively.
jeemain
chemistry
past papers
2018
68
asked
Dec 11, 2018
by
pady_1
0
answers
The ratio of mass percent of $C$ and $H$ of an organic compound $(C_XH_YO_Z)$ is $6:1$. If one molecule of the above compound $(C_XH_YO_Z)$ contains half as much oxygen as required to burn one molecule of compound $C_XH_Y$ completely to $CO_2$ and $H_2O$. The empirical formula of compound $C_XH_YO_Z$ is :
jeemain
chemistry
past papers
2018
67
asked
Dec 11, 2018
by
pady_1
0
answers
The trans-alkenes are formed by the reduction of alkynes with ?
jeemain
chemistry
past papers
2018
66
asked
Dec 11, 2018
by
pady_1
0
answers
An alkali is titrated against an acid with methyl orange as indictor, which of the following is a correct combination ?
jeemain
chemistry
past papers
2018
65
asked
Dec 11, 2018
by
pady_1
0
answers
The increasing order of basicity of the following compounds is :<br>
jeemain
chemistry
past papers
2018
64
asked
Dec 11, 2018
by
pady_1
0
answers
Phenol reacts with methyl chloroformate in the presence at $NaOH$ to form product A. A reacts with $Br_4$ to form product B. A and B respectively
jeemain
chemistry
past papers
2018
63
asked
Dec 11, 2018
by
pady_1
0
answers
Which of the following salts is the most basic in aqueous solution ?
jeemain
chemistry
past papers
2018
62
asked
Dec 11, 2018
by
pady_1
0
answers
The total number of lone pair of electrons in $I^-_3$ ion is :
jeemain
chemistry
past papers
2018
61
asked
Dec 11, 2018
by
pady_1
0
answers
Let the orthocenter and centroid of a triangle be A (-3, 5) and B (3, 3) respectively. If C is the circumcentre of this triangle, then the radius of the circle having line segement AC as diameter, is :
jeemain
math
past papers
2018
60
asked
Dec 11, 2018
by
pady_1
0
answers
Let A be the sum of the first 20 terms and B be sum of the first 40 terms of the series $1^2 + 2.2^2 + 3^2 + 2.4^2 + 5^2+2.6^2 + ...$ If $B - 2A = 100 \lambda$, then $\lambda$ is equal to :
jeemain
math
past papers
2018
59
asked
Dec 11, 2018
by
pady_1
0
answers
From 6 different novels and 3 different dictionaries, 4 novels and 1 dictionary are to be selected and arranged in a row on a shelf so that the dictionary is always in the middle. The number of such arrangements is :
jeemain
math
past papers
2018
58
asked
Dec 11, 2018
by
pady_1
0
answers
The length of the projection of the line segment joining the points $(5, -1, 4)$ and $(4, -1, 3)$ on the plane, $x+y+z=7$ is
jeemain
math
past papers
2018
56
asked
Dec 11, 2018
by
pady_1
0
answers
Let $\overrightarrow{u}$ be a vector coplanar with the vectors $\overrightarrow{a} = 2 \hat{i} + 3 \hat{j} - \hat{k} $ and $\overrightarrow{b} = \hat{j} + \hat{k}$. If $\overrightarrow{u}$ is perpendicular to and $\overrightarrow{a}$ and $\overrightarrow{u} \overrightarrow{b} = 24$, then $| \overrightarrow{u}|^2$ is equal to :
jeemain
math
past papers
2018
55
asked
Dec 11, 2018
by
pady_1
0
answers
Let $y = y(x)$ be the solution of the differential equation <br> $\sin x \frac{dy}{dx} + y \cos x = 4 x, \; x \subset (0, \pi)$. If $y (\frac{\pi}{2})=0$, then $y (\frac{\pi}{6})$ is equal to
jeemain
math
past papers
2018
54
asked
Dec 11, 2018
by
pady_1
0
answers
Let $S = \{ t \in R : f(x) = |x-\pi|. (e^{|x|} - 1) \sin |x|$ is not differentiable at $t\}$. Then the set $S$ is equal to :
jeemain
math
past papers
2018
53
asked
Dec 11, 2018
by
pady_1
0
answers
The integral <br> $\begin{align*} \int \frac{\sin^2 x \cos^2 x}{(\sin^5 x + \cos^3 x \sin^2 x + \sin^3 x \cos^2x + \cos^5x)^2} \end{align*} \; dx$ is equal to:<br> (where C is a constant of integration)
jeemain
math
past papers
2018
52
asked
Dec 11, 2018
by
pady_1
0
answers
If $\displaystyle\sum_{i=1}^{9} (x_i - 5) = 9$ and $ \displaystyle\sum_{i=1}^{9} (x_i - 5)^2 = 45$ then the standard deviation of the 9 items $x_1, \; x_2, .... x_9$ is :
jeemain
math
past papers
2018
51
asked
Dec 11, 2018
by
pady_1
0
answers
For each $t \in R$ let $[t]$ be the greatest integer less than or equal to $t$. Then <br> $ \displaystyle\lim_{x \to 0^-} x$ $\begin{pmatrix} [\frac{1}{x} +[\frac{2}{x}] +....+[\frac{15}{x}] \end{pmatrix}$
jeemain
math
past papers
2018
50
asked
Dec 11, 2018
by
pady_1
0
answers
Let $g(x) = \cos x^2, \; f(x) = \sqrt{x}$ and $\alpha, \;\beta \;(\alpha < \beta)$ be the roots of the quadratic equation $18x^2-9 \pi x + x^2 = 0$. Then the area (in sq. units) bounded by the curve $y=(gof)(x) $ and the lines $x = \alpha,\; x = \beta$ and $y =0$, is
jeemain
math
past papers
2018
49
asked
Dec 11, 2018
by
pady_1
0
answers
The value of $\begin{align*} \int_{-\frac{\pi}{2}}^{\frac{\pi}{2}} \frac{\sin^2 x}{1+2^x} dx \end{align*}$ is :
jeemain
math
past papers
2018
48
asked
Dec 11, 2018
by
pady_1
0
answers
A straight line through a fixed point $(2, 3)$ intersects the coordinate axes at distinct points P and Q. If O is the origin and the rectangle OPRQ is completed, then the locus of R is
jeemain
math
past papers
2018
47
asked
Dec 11, 2018
by
pady_1
0
answers
Let $a_1, a_2, a_3,.....,a_{49}$ be in A.P. such that $\displaystyle\sum_{k=0}^{12} a_{4k+1}=416$ and $a_9 + a_{43} =66$. <br> If $a_1^2 + a_2^2....a_{17}^2=140\;m$ then $m$ is equal to :
jeemain
math
past papers
2018
46
asked
Dec 11, 2018
by
pady_1
0
answers
The sum of the co-effiicients of all odd degree terms in the expansion of $(x + \sqrt{x^3-1})^5 + (x-\sqrt{x^3 - 1})^5, (x>1)$ is :
jeemain
math
past papers
2018
45
asked
Dec 11, 2018
by
pady_1
0
answers
If $\begin{vmatrix} x-4 & 2x & 2x \\ 2x & x-4 & 2x \\ 2x & 2x & x-4 \end{vmatrix}= (A + Bx)(x-A)^2$<br> then the ordered pair (A, B) is equal to :
jeemain
math
past papers
2018
44
asked
Dec 11, 2018
by
pady_1
0
answers
Tangent and normal are drawn at $P(16, 16)$ on the parabola $y^2 =16x$, which intersect the axis of the parabola at A and B, respectively. If $C$ is the centre of the circle through the points $P, \;A$ and $B$ and $\angle CPB=\theta$, then a value of $\tan \theta$ is :
jeemain
math
past papers
2018
43
asked
Dec 11, 2018
by
pady_1
0
answers
The Boolean expression $\sim (p \lor q) \lor (\sim p \land q)$ is equivalent to :
jeemain
math
past papers
2018
42
asked
Dec 11, 2018
by
pady_1
0
answers
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