Chemistry_Today_April_2017_vk_com_stopthepress

16. In a car race sound signals emitted by the two cars are
detected by the detector on the straight track at the
end point of the race. Frequency observed are 330 Hz
and 360 Hz and the original frequency is 300 Hz of
both cars. Race ends with the separation of 100 m
between the cars. Assume both cars move with
constant velocity and velocity of sound is 330 m s –1 .
Find the time (in second) taken by winning car.
17. A parallel plate capacitor is maintained at a
certain potential difference. When a 3 mm
thick slab is introduced between the plates, in
order to maintain the same potential difference,
the distance between the plates is increased by
2.4 mm. What is the dielectric constant of the slab?
18. A silver sphere of radius 1 cm and work function
4.7 eV is suspended from an insulating thread in
free-space. It is under continuous illumination of
200 nm wavelength light. As photoelectrons are
emitted, the sphere gets charged and acquires a
potential. The maximum number of photoelectrons
emitted from the sphere is A × 10 Z (where 1 < A < 10).
The value of Z is
CHEMISTRY
SECTION 1 (Maximum Marks : 15)
• This section contains FIVE questions.
• Each question has FOUR options (a), (b), (c) and (d). ONLY
ONE of these four options is correct.
• For each question, darken the bubble corresponding to the
correct option in the ORS.
• For each question, marks will be awarded in one of the following
categories :
Full Marks : +3 If only the bubble corresponding to the correct
option is darkened.
Zero Marks : 0 If none of the bubbles is darkened.
Negative Marks : –1 In all other cases.
19. Following is the graph between
(a – x) –1 and time ‘t’ for a
second order reaction.
(q = tan –1 (0.5), OA = 2 L mol –1 )
Hence, rate at the start of the
reaction is
( a–x ) –1
A
O time () t
(a) 1.25 mol –1 min –1 (b) 0.5 mol L –1 min –1
(c) 0.125 mol L –1 min –1 (d) 1.25 mol L –1 min –1
20. When a person is deprived of food, in which order
does the body use the following sources to produce
glucose?
I. Protein breaks down to amino acids used for
gluconeogenesis
II. Conversion of glycogen to glucose
III. Catabolism of liquids
(a) I, II and III (b) III, II and I
(c) II, I and III (d) II, III and I
21. A gas expands isothermally against a constant
external pressure of 1 atm from a volume of 10 dm 3
to a volume of 20 dm 3 . It absorbs 800 J of thermal
energy from its surroundings. The DU is
(a) –321 J (b) + 123 J (c) –213 J (d) + 231 J
22. The edge length of unit cell of a metal, (having
molecular weight 75 g/mol) which crystallises in
cubic lattice, is 5 Å. If the density is 2 g/cc, then the
radius of metal atom is (N A = 6 × 10 23 )
(a) 2.165 Å
(b) 2.865 Å
(c) 1.716 Å
(d) 3.121 Å
23. The given graph represents the
S
plots of solubility (in mg/100 g)
R
of different gases (P, Q, R, S)
Q P
versus pressure. Predict the gas
which has the highest value of
Henry’s law constant.
Pressure
(a) P (b) Q (c) R (d) S
SECTION 2 (Maximum Marks : 32)
• This section contains EIGHT questions.
• Each question has FOUR options (a), (b), (c) and (d). ONE OR
MORE THAN ONE of these four option(s) is(are) correct.
• For each question, darken the bubble(s) corresponding to all
the correct option(s) in the ORS.
• For each question, marks will be awarded in one of the following
categories :
Full Marks : +4 If only the bubble(s) corresponding to the
correct option(s) is(are) darkened.
Partial Marks : +1 For darkening a bubble corresponding
to each correct option, provided NO incorrect option is
darkened.
Zero Marks : 0 If none of the bubbles is darkened.
Negative Marks : –2 In all other cases.
• For example, if (a), (c) and (d) are all the correct options for
a question, darkening all these three will result in +4 marks;
darkening only (a) and (d) will result in +2 marks; and darkening
(a) and (b) will result in –2 marks, as a wrong option is also
darkened.
24. Select correct stereochemistry (chiral/achiral) of
the reactants and products.
(a) HO
(b)
HO
O
achiral
achiral
CO Et 2
Solubility (mg/100 g)
CO 2 H HO
H +
biological
reduction
O
chiral
OH
CO2Et
chiral
O
CHEMISTRY TODAY | APRIL ‘17 29