Chemistry_Today_April_2017_vk_com_stopthepress

5. Compound 'X' C 7
H 8
O, is insoluble in H 2
O,
dil. HCl and aq. NaHCO 3
but dissolves in dil. NaOH.
When 'X' is treated with Br 2
/H 2
O, it is converted
rapidly into a compound of formula, C 7
H 5
OBr 3
.
The compound 'X' is
(a) o-cresol (b) p-cresol
(c) m-cresol (d) anisole.
6. 1.0 g of a monobasic acid HA in 100 g water lowers
the freezing point by 0.385 K. If 0.3 g of same acid
requires 25 mL of N/5 NaOH solution for complete
neutralisation, then % degree of ionisation of acid is
(K f
of H 2
O = 1.86 K kg mol –1 )
(a) 18% (b) 24% (c) 42% (d) 64%
7. Some physical properties of four elements L, M, Q
and R are given below in the table:
Physical L M Q R
properties
M.pt. (°C) –7 63 –189 1083
B.pt. (°C) 58 766 –186 2582
Colour at
STP
dark
red
silvery colourless
browny
-red
Density at 3.1 0.86 1.7 × 10 –3 8.9
STP
(g cm –3 )
These elements in the order L, M, Q and R are from
the following groups in the periodic table.
L
(a) group 1
M
transition
Q
group 17
R
group
elements
zero
(b) group 17 group 1 group transition
zero elements
(c) group 17 transition group group 1
elements zero
(d) transition
elements
group 1 group 17 group
zero
SECTION–II
(MULTIPLE CORRECT ANSWER TYPE)
This section contains 4 multiple choice questions. Each
question has four choices (a), (b), (c) and (d) out of which
ONE or MORE may be correct. For correct answer 4 marks
will be awarded, no negative marks in this section.
CH 3 O CH 3
8. Ph C NH 2+ HO C CH CH 2 5 ( ) +( )
( R + )
H
(Racemic mixture)
R–form
(Purely optically
active)
The correct statement(s) regarding compounds
(A) and (B) is/are
(a) both are optically active in nature
(b) relation between (A) and (B) is diastereomers
(c) (A) and (B) are meso compounds
(d) out of (A) and (B), one is optically active and
other is optically inactive.
9. Among the following, identify the correct
statement(s) ?
(a) The number of atoms in 100 g of an fcc crystal
with density, (ρ = 10 g cm –3 ) and cell edge
200 pm are 5 × 10 24 .
(b) Sr–90 radioisotope (t 1/2
= 27 years) obtained
as one of the fission products of Uranium–235.
The time required for 1.00 g of the isotope to
be reduced to 0.2 g by decay is ≈ 63 years.
(c) The rate of uncatalysed reaction at 127°C is equal
to that of the catalysed reaction at 27°C. The
catalyst lowers the activation energy by 25%.
(d) Barium permanganate [Ba(MnO 4
) 2
] oxidises
ferrous oxalate in dil. H 2
SO 4
and itself is reduced
to MnSO 4
. The volume of 0.1 M [Ba(MnO 4
) 2
]
is needed to oxidise 50 mL of 0.2 M ferrous
oxalate in acidic medium is 30 mL.
10. Decomposition of 3A (g)
→ 2B (g)
+ 2C (g)
follows
first order kinetics, initially only A is present in the
container. Pressures developed after 20 min and
infinite time are 3.5 and 4 atm, respectively. Which
one is correct?
(a) t 50%
= 20 min (b) t 75%
= 40 min
(c) t 99%
= 64/3 min (d) t 87.5%
= 60 min
11.
(a)
R =
(b) Q =
(c)
Q =
OH
OH
NaOH
1 eq.
O
O
Cl O
CH 2
C Cl
P
O
O
O
CH2
C Cl
OH
O
C O
–
O CH2
Cl
Q
NaOH
R
20 CHEMISTRY TODAY | APRIL ‘17