ANSWERS FOR QUESTIONS OF 22-10-2007

1. C
2. A
3. B

Questions for 22-10-2007

1.

STATEMENT-1: Molecules that are not superimposable on their mirror images are chiral.

Because

STATEMENT-2: All chiral molecules have chiral centres.

(A) Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation for Statement-1
(B) Statement-1 is True, Statement-2 is True; Statement-2 is not a correct explanation for Statement-1
(C) Statement-1 is True, Statement-2 is False
(D) Statement-1 is False, Statement-2 is True




2. In the experiment to determine the speed of sound using a resonance column,
(A) prongs of the tuning fork are kept in a vertical plane
(B) prongs of the tuning fork are kept in a horizontal plane
(C) in one of the two resonances observed, the length of the resonating air column is close to the wavelength of sound in air
(D) in one of the two resonances observed, the length of the resonating air column is close to half the wavelength of sound in air



3. If a, b, c be unit vectors such that a + b + c = 0. Which one of the following is correct?
(A) a × b = b × c = c × a = 0
(B) a × b = b × c = c × a is not equal to 0
(C) a × b = b × c = a × c is not equal to 0
(D) a × b, b × c, c × a are mutually perpendicular

Answers for questions on 21-10-2007

to be posted

Questions for 21-10-2007

1. A student performs an experiment to determine the Young’s modulus of a wire, exactly 2m long, by Searle’s method. In a particular reading, the student measures the extension in the length of the wire to be 0.8 mm with an uncertainty of ± 0.05 mm at a load of exactly 1.0 kg. The student also measures the diameter of the wire to be 0.4 mm with an uncertainty of ± 0.01 mm. Take g = 9.8 m/s^2 (exact). The Young’s modulus obtained from the reading is

(A) (2.0 ± 0.3)*10^11 N/m^2
(B) (2.0 ± 0.2)*10^11 N/m^2
(C) (2.0 ± 0.1)*10^11 N/m^2
(D) (2.0 ± 0.05)*10^11 N/m^2






2.Consider a titration of potassium dichromate solution with acidified Mohr’s salt solution using diphenylamine as indicator.

The number of moles of Mohr’s salt required per mole of dichromate is
(A) 3 (B) 4 (C) 5 (D) 6



IIT.JEE 2007 SOLUTIONS.MATHEMATICS
3. The letters of the word COCHIN are permuted and all the permutations are arranged in an alphabetical order as in an English dictionary. The number of words that appear before the word COCHIN is


(A) 360 (B) 192 (C) 96 (D) 48

Answers to Questions of 20-10-2007

1.B
2.A
3.A

Questions for 20-10-2007

1.

Statement - 1
If the accelerating potential in an X-ray tube is increased, the wavelengths of the characteristic X-rays do not change.

Because

Statement - 2
When an electron beams strikes the target in an X-ray tube, part of the kinetic energy is converted into X-ray energy.

(A) Statement – 1 is True, Statement – 2 is True; Statement – 2 is a correct explanation for
statement – 1
(B) Statement – 1 is True, Statement – 2 is True; Statement – 2 is Not a correct explanation for
Statement – 1.
(C) Statement – 1 is True, Statement – 2 is False
(D) Statement – 1 is False, Statement – 2 is True




2.
When 20 g of naphthoic acid (C-11 H-8 O-2) is dissolved in 50 g of benzene  [K(f) = 1.72 K kg mol^ -1], a freezing point depression of 2 K is observed. The van’t Hoff factor (i) is

(A) 0.5
(B) 1
(C) 2
(D) 3



3.

Tangents are drawn from the point (17, 7) to the circle x^2 + y^2 = 169.

Statement - 1
The tangents are mutually perpendicular.

Because

Statement - 2
The locus of the points from which mutually perpendicular tangents can be drawn to the given circle is x^2 + y^2 = 338.

(A) Statement – 1 is True, Statement – 2 is True; Statement – 2 is a correct explanation for statement – 1
(B) Statement – 1 is True, Statement – 2 is True; Statement – 2 is Not a correct explanation for Statement – 1.
(C) Statement – 1 is True, Statement – 2 is False
(D) Statement – 1 is False, Statement – 2 is True

Answers to Questions of 19-10-2007

1.C
2.C
3.C

Questions for 19-10-2007

1.

Statement – 1

A block of mass m starts moving on a rough horizontal surface with a velocity v. It stops due to
friction between the block and surface after moving through a certain distance. The surface is
now tilted to an angle 30° with the horizontal and the same block is made to go up on the surface
with the same initial velocity v. The decrease in the mechanical energy in the second situation is
smaller than that in the first situation.
Because

Statement - 2
The coefficient of friction between the block and the surface decreases with the increase in the
angle of inclination.


(A) Statement – 1 is True, Statement – 2 is True; Statement – 2 is a correct explanation for
statement – 1
(B) Statement – 1 is True, Statement – 2 is True; Statement – 2 is Not a correct explanation for
Statement – 1.
(C) Statement – 1 is True, Statement – 2 is False
(D) Statement – 1 is False, Statement – 2 is True

2.

STATEMENT.1: Glucose gives a reddish.brown precipitate with Fehling’s solution.

Because

STATEMENT.2: Reaction of glucose with Fehling’s solution gives CuO and gluconic acid.


(A) Statement.1 is True, Statement.2 is True; Statement.2 is a correct explanation for Statement.1.
(B) Statement.1 is True, Statement.2 is True; Statement.2 is NOT a correct explanation for Statement.1.
(C) Statement.1 is True, Statement.2 is False.
(D) Statement.1 is False, Statement.2 is True.


3.

The differential equation dy/dx = [SQRT(1-y^2)]/y
determines a family of circles with

(A) variable radii and a fixed centre at (0, 1)
(B) variable radii and a fixed centre at (0, –1)
(C) fixed radius 1 and variable centres along the x-axis
(D) fixed radius 1 and variable centres along the y-axis

Answers for questions of 18-10-2007

1.C
2.A
3.D

Questions for 18-10-2007

1.

Statement - 1

The formula connecting u, v and f for a spherical mirror is valid only for mirrors whose sizes are very small compared to their radii of curvature.

Because
Statement - 2

Laws of reflection are strictly valid for plane surfaces, but not for large spherical surfaces

(A) Statement – 1 is True, Statement – 2 is True; Statement – 2 is a correct explanation for
statement – 1
(B) Statement – 1 is True, Statement – 2 is True; Statement – 2 is Not a correct explanation for
Statement – 1.
(C) Statement – 1 is True, Statement – 2 is False
(D) Statement – 1 is False, Statement – 2 is True


2.

Statement - 1
Boron always forms covalent bond

Because
Statement - 2

The small size of B^3+favours formation of covalent bond.

(A) Statement – 1 is True, Statement – 2 is True; Statement – 2 is a correct explanation for statement – 1
(B) Statement – 1 is True, Statement – 2 is True; Statement – 2 is Not a correct explanation for Statement – 1.
(C) Statement – 1 is True, Statement – 2 is False
(D) Statement – 1 is False, Statement – 2 is True

3. Let F(x) be an indefinite integral of sin^2 x.

Statement - 1

The function F(x) satisfies F(x +Pi) = F(x) for all real x.

Because

Statement - 2

sin^2 (x+ Pi) = sin^2 x for all real x.

(A) Statement – 1 is True, Statement – 2 is True; Statement – 2 is a correct explanation for statement – 1
(B) Statement – 1 is True, Statement – 2 is True; Statement – 2 is Not a correct explanation for Statement – 1.
(C) Statement – 1 is True, Statement – 2 is False
(D) Statement – 1 is False, Statement – 2 is True

Answers to Questions of 17-10-2007

1. B

2. A

3. B

Q's for the day 17-10-2007

1. The size of the image of an object, which is at infinity, as formed by a convex lens of focal length 30 cm is 2 cm. If a concave lens of focal length 20 cm is placed between the convex lens and the image at a distance of 26 cm from the convex lens, calculate the new size of the image.


(A) 1.25 cm (B) 2.5 cm
(C) 1.05 cm (D) 2 cm





2. Among the following, the molecule with the highest dipole moment is:

(A) CH-3Cl (B) CH-2Cl-2
(C) CHCl-3 (D) CCl-4





3. The number of integral points (integral point means both the coordinates should be integer) exactly in the interior of the triangle with vertices (0, 0), (0, 21) and (21, 0), is

(A) 133 (B) 190
(C) 233 (D) 105

1. Final temperature is 0 degress celsius

2. A

3. 216 or 217 pm

Questions for 2-10-2007

1. In an insulated vessel, 0.05 kg steam at 373 K and 0.45 kg of ice at 253 K are mixed. Then, find the final temperature of the mixture.

Given, L(fusion) = 80 cal/g = 336 J/g, L(vaporization) = 540 cal/g = 2268 J/g,
S(ice) = 2100 J/kg K = 0.5 cal/gK and S(water) = 4200 J/kg K = 1 cal /gK

2. If f″(x) = − f(x) and g(x) = f′(x) and F(x) = [f(x/2)]^2 + [g(x/2)]^2 and given that F(5) = 5 then F(10) is equal to

(A) 5
(B) 10
(C) 0
(D) 15



3. The edge length of unit cell of a metal having molecular weight 75 g/mol is 5
A^0 which crystallizes in cubic lattice. If the density is 2 g/cc then find the radius of metal atom. [N(A) = 6 × 10^23]. Give the answer in pm.

Answers for Questions of 1-10-2007

1. All A,B,C,D

2. B

3. A

Questions for 1-10-2007

1. In a dark room with ambient temperature T0, a black body is kept at a temperature T. Keeping the temperature of the black body constant (at T), sunrays are allowed to fall on the black body through a hole in the roof of the dark room. Assuming that there is no change in the ambient temperature of the room, which of
the following statement(s) is/are correct?


(A) The quantity of radiation absorbed by the black body in unit time will increase.
(B) Since emissivity = absorptivity, hence the quantity of radiation emitted by black body in unit time will increase.
(C) Black body radiates more energy in unit time in the visible spectrum.
(D) The reflected energy in unit time by the black body remains same.

2. The smallest ketone and its next homologue are reacted with NH-2OH to form oxime.

(A) Two different oximes are formed
(B) Three different oximes are formed
(C) Two oximes are optically active
(D) All oximes are optically active

3. If 0 < θ < 2π, then the intervals of values of θ for which 2 sin^2θ − 5 sinθ + 2 > 0, is


A. (0,π/6)∪(5π/6, 2π)
B. (π/8, 5π/6)
C. (0,π/8)∪(π/6, 5π/6)
D. (41π/48, π)

Answers for 30-9-2007

1. A - P
B - R
C - R
D - P, Q, S



2. C


3. D

IIT JEE Questions for 30-9-2007

1. A simple telescope used to view distant objects has eyepiece and objective lens of focal lengths fe and f0,
respectively. Then

Column I------------------------------------------ Column II
(A) Intensity of light received by lens---------- (P) Radius of aperture (R)
(B) Angular magnification------------------------ (Q) Dispersion of lens
(C) Length of telescope-------------------------- (R) focal length f0, fe
(D) Sharpness of image--------------------------- (S) spherical aberration

2. The IUPAC name of C-6H-5COCl is

(A) Benzoyl chloride
(B) Benzene chloro ketone
(C) Benzene carbonyl chloride
(D) Chloro phenyl ketone

3. Integral of [(x^2-1)/(x^3*(SQRT(2x^4-2x^2+1))]

(A) [(SQRT(2x^4-2x^2+1)/x^2] + c
(B) [(SQRT(2x^4-2x^2+1)/x^3] +c
(C) [(SQRT(2x^4-2x^2+1)/x] + c
(D) [(SQRT(2x^4-2x^2+1)/2x^2] + c

Answers for the questions of 29-9-2007

1. A,B,D

2. A----P,R
B----P,R
C----Q
D----S

3. C,D

Question for the Day 29.9.2007

1. Function x = A sin^2 ωt + B cos^2 ωt + C sin ωt cos ωt represents Simple Harmonic Motion



(A) for any value of A, B and C (except C = 0)
(B) if A = −B; C = 2B, amplitude = Absolute value of (B*SQRT(2))
(C) if A = B; C = 0
(D) if A = B; C = 2B, amplitude = Absolute value of B

Multiple solutions possible



2. . Match the extraction processes listed in Column I with metals listed in Column II:
Column I --------------------------------- Column II
(A) Self reduction -------------------------- P. Lead
(B) Carbon reduction-------------------------- Q. Silver
(C) Complex formation and -------------------- R. Copper
displacement by metal
(D)Decomposition of iodide-------------------- S. Boron

3. A tangent drawn to the curve y = f(x) at P(x, y) cuts the x-axis and y-axis at A and B respectively such that BP : AP = 3:1, given that f(1) = 1, then

(A) equation of curve is x(dy/dx) - 3y = 0
(B) normal at (1, 1) is x + 3y = 4
(C) curve passes through (2, 1/8)
(D) equation of curve is x(dy/dx)+3y = 0

Note: multiple solutions possible

Answers for Questions of 28/9/2007

1. C and D

2. A

3. A

Questions fo 28-9-=2007

1. A solid cylinder of mass m and radius r is rolling on a rough inclined plane of inclination θ. The coefficient of friction between the cylinder and incline is μ. Then


(A)frictional force is always μmg cos θ
(B)friction is a dissipative force
(C)by decreasing θ, frictional force decreases
(D)friction opposes translation and supports
rotation.

Note: Multiple alternatives possible.

2.
The coordination number of Ni(2+) ion is 4.

NiCl-2 + KCN (excess) → A (cyano complex)
NiCl-2 + Conc. HCl (excess) → B (chloro complex)


The IUPAC name of A and B are
(A) Potassium tetracyanonickelate (II), potassium tetrachloronickelate (II)
(B) Tetracyanopotassiumnickelate (II), teterachlorpotassiumnickelate (II)
(C) Tetracyanornickel (II), tetrachloronickel (II)
(D) Potassium tetracyanonickel (II), potassium tetrachloronickel (II)

3. Let a, b, c be the sides of a triangle. No two of them are equal and λ ∈ R. If the roots of the equation x^2 + 2(a + b+ c) x
+ 3λ (ab + bc + ca) = 0 are real, then
(A) λ < 4/3
(B) λ > 5/3
(C)λ can be any value between 1/3 and 5/3
(D)λ is higher than 4/3 but less than 5/3

Answers for Q of 27-9-2007

1. A

2. D

3. C

Question for the Day 27-9-2007

1. A solid sphere of mass M, radius R and having moment of inertia about an axis passing through the centre of mass as I, is recast into a disc of thickness t, whose moment of inertia about an axis passing through its edge and perpendicular to its plane remains I. Then, radius of the disc will be


(A) 2R/SQRT(15)


(B) R*SQRT(2/15)


(C) 4R/SQRT(15)

(D) R/4

2. CuSO-4 decolourises on addition of KCN, the product is


(A) Cu(CN)-4 (B) [Cu(CN)-3
(C) Cu(CN)-2 (D) CuCN

3. Given an isosceles triangle, whose one angle is 120° and radius of its incircle = SQRT(3) . Then the area of the triangle in sq.units is

(A) 7 + 12*SQRT(3) (B) 12 − 7*SQRT( 3)

(C) 12 + 7*SQRT( 3) (D) 4π

Answers to Q of 26-9-2007

1. B

2. A

3. C

Question for the Day 26-9-2007

1. A biconvex lens of focal length f forms a circular image of sun of radius r in focal plane. Then
(A) πr^2 ∝ f
(B) πr^2 ∝ f^2
(C) if lower half part is covered by black sheet, then area of the image is equal to πr^2/2
(D) if f is doubled, intensity will increase

2.MgSO-4 on reaction with NH-4OH and Na-2HPO-4 forms a white crystalline precipitate. What is its formula?

(A) Mg(NH-4)PO-4
(B) Mg-3(PO-4)-2
(C) MgCl-2.MgSO-4
(D) MgSO-4


3. For x > 0, Lim[(Sin)^(1/x)+(1/x)^sinx)] is
(x -> 0)
(A) 0
(B) -1
(C) 1
(D) 2

Answers for Q for 25-9-2007

1. C

2. A

3. A

Questions for the Day 25-9-2007

1. Orthocentre of triangle with vertices (0, 0), (3, 4) and (4, 0) is
(A) (3, 5/4)
(B) (3, 12)
(C) (3, 3/4)
(D) (3, 9)


2. During depression of freezing point in a solution the following are in equilibrium
(A) liquid solvent, solid solvent (B) liquid solvent, solid solute
(C) liquid solute, solid solute (D) liquid solute solid solvent

3. A cube has a side of length 1.2 × 10^−2m. Calculate its volume.
(A) 1.7 × 10^−6 m^3. (B) 1.73 × 10^−6 m^3.
(C) 1.70 × 10^−6 m^3. (D) 1.732 × 10^−6 m^3.

Ganeshaya Namah

I started all blogs related to my relearning of Physics, Chemistry, and Mathematics with aim of facilitating my daughter study of XI&XII and competitive examinations seeking blessings of Ganesha. I hope my experience in this endeavour becomes useful to many other children in learning their subjects much more thoroughly. When we prepare for a competitive examination in earnest, even if we do not get the reward in the competitive examination, the reward of knowledge will certainly come to us. All of us should do our best till the day of our examination and then accept the result as it comes. I feel this is the message of Bhagavadgita. You have all right and might to do all you can do to get a result, but you have no right to demand the result because you have done your best effort.

I once again salute Lord Ganesh and seek his blessing in this mission of helping my child and other children.

Nrao