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Previous Year Question Papers NEET 2016 Phase II- Chemistry

13941.A given nitrogen-containing aromatic compound A reacts with Sn/HCl, followed by HNO2 to give an unstable compound B. B, on treatment with phenol, forms a beautiful coloured compound C with the molecular formula C12H10N2O. The structure of compound A is
C6H5CONH2
C6H5NH2
C6H5NO2
C6H5CN
Explanation:
reaction result C12H10N2O
13942.Consider the reaction

CH3CH2CH2Br + NaCN → CH3CH2CH2CN + NaBr

This reaction will be the fastest in
water
ethanol
methanol
N,N-dimethylformamide (DMF)
Explanation:
polar aprotic solvent

CH3CH2CH2Br + NaCN → CH3CH2CH2CN + NaBr

This is a SN2 Reaction for which polar aprotic medium is suitable for faster rate of reaction.

13943.The correct structure of the product A formed in the reactionC6H5O reaction question
is
 C6H5OH+
C6H5OH
C6H5O
C6H5OH
Explanation:
reaction result C6H5O

During hydrogenation of α, β unsaturated carbonyl compound by Pd catalyst selective reduction is observed of double bond.

13944.Which among the given molecules can exhibit tautomerism?tautomerism options
Both II and III
III only
Both I and III
Both I and II
Explanation:

α-H at bridge head carbon never show tautomerism.

tautomerism result
13945.The correct order of strengths of the carboxylic acidscarboxylic acids ordering
is
II > I > III
I > II > III
II > III > I
III > II > I
Explanation:
(II > III > I)

Acidic strength α –I, –M effect

–I effect depend upon distance so II have stronger –I effect than III.

13946.The compound that will react most readily with gaseous bromine has the formula:
C2H4
C3H6
C2H2
C4H10
Explanation:

Bromine naturally exist in liquid phase and in question bromine is given in gaseous phase.

bromine liquid to gas reaction

Reaction takes place at high temperature so mechanism with Br2(g) should be free radical substitution which can take place in propene and butane.

Rate of free radical substitution reaction depend upon stability of free radical.

free radical substitution

Propenyl free radical is more stable so answer will be C3H6

13947.Which one of the following compounds shows the presence of intramolecular hydrogen bond?
Concentrated acetic acid
H2O2
HCN
Cellulose
Explanation:

Cellulose is example of intramolecular H-bonding.

13948.The molar conductivity of a 0.5 mol / dm3 solution of AgNO3 with electrolytic conductivity of 5.76 × 10-3 S cm-1 at 298 K is
28.8 S cm2 /mol
2.88 S cm2 /mol
11.52 S cm2 /mol
0.086 S cm2 /mol
Explanation:

$\lambda^{o}_{M} = \dfrac{k \times 1000}{M} = \dfrac{5.76 \times 10^{-3} \times 1000}{0.5}$

= 11.52 S cm2 mol-1

13949.The decomposition of phosphine (PH3) on tungsten at low pressure is a first-order reaction. It is because the
Rate of decomposition is very slow
Rate is proportional to the surface coverage
Rate is inversely proportional to the surface coverage
Rate is independent of the surface coverage
Explanation:

phosphine decomposition reaction

Rate = k[PH3]

It is dependent on surface coverage because at low pressure, surface area covered is proportional to partial pressure of PH3 and it is first order w.r.t PH3.

θ = $\dfrac{kP}{1 + kP}$

θ = fraction of surface area covered at low pressure

θ = k P

13950.The coagulation values in millimoles per litre of the electrolytes used for the coagulation of As2S3 are given below:

I. (NaCl) = 52,     II. (BaCl2) = 0.69     III. (MgSO4) = 0.22

The correct order of their coagulating power is
III > I > II
I > II > III
II > I > III
III > II > I
Explanation:

$Coagulation \ power \propto \dfrac{1}{Coagulation \ value}$

Higher the coagulation power, lower is the coagulation values in millimoles per litre.

MgSO4 > BaCl2 > NaCl.

13951.During the electrolysis of molten sodium chloride, the time required to produce 0.10 mol of chlorine gas using a current of 3 amperes is
330 minutes
55 minutes
110 minutes
220 minutes
Explanation:

At Cathode:

NACl electrolysis cathode reaction

At anode:

NACl electrolysis anode reaction

$\dfrac{W}{E} = \dfrac{It}{96500}$

0.1 × 2 = $\dfrac{3 × t(sec)}{96500}$

t = 6433 sec

t = 107.2 min

∼ 110 min.

13952.How many electrons can fit in the orbital for which n = 3 and l = 1 ?
14
2
6
10
Explanation:
n = 3     l = 1

3p orbital can have only 2 electrons.

13953.For a sample of perfect gas when its pressure is changed isothermally from pi to pf, the entropy change is given by
$\triangle S = RT \ln \left(\dfrac{p_{i}}{p_{f}}\right)$
$\triangle S = nR \ln \left(\dfrac{p_{f}}{p_{i}}\right)$
$\triangle S = nR \ln \left(\dfrac{p_{i}}{p_{f}}\right)$
$\triangle S = nRT \ln \left(\dfrac{p_{f}}{p_{i}}\right)$
Explanation:

$\triangle S_{sys} = nR \ ln\dfrac{P_1}{P_2} \ + \ nCP\ ln\dfrac{T_2}{T_1}$

In isothermal process T1 = T2

$\triangle S_{sys} = nR \ln\dfrac{P_i}{P_f}$

13954.The vant Hoff factor (i) for a dilute aqueous solution of the strong electrolyte barium hydroxide is
3
0
1
2
Explanation:

Ba(OH)2 → Ba+2 + 2OH

i = 3

13955.The percentage of pyridine (C5H5N) that forms pyridinium ion (C5H5N+H) in a 0.10 M aqueous pyridine solution (Kb for C5H5N = 1.7 × 10–9) is
1.6 %
0.0060 %
0.013 %
0.77 %
Explanation:

C5H5N + H5O → C5H5N+H + OH

$α = \sqrt{\dfrac{K_b}{c}} = \sqrt{\dfrac{1.7 \times 10^{-9}}{0.1}} = \sqrt{1.7 \times 10^{-8}}$

% α = 1.3 × 10–4 ×100

= 1.3 × 10–2 = 0.013.

13956.In calcium fluoride, having the fluorite structure, the coordination numbers for calcium ion (Ca2+) and fluoride ion (F) are
4 and 8
4 and 2
6 and 6
8 and 4
Explanation:

Ca2+ is surrounded by 8F

F is surrounded by 4Ca+2

13957.If the $E_{cell}^0$ for a given reaction has a negative value, which of the following gives the correct relationships for the values of ΔG0 and Keq?
ΔG0 < 0; Keq < 1
ΔG0 > 0; Keq < 1
ΔG0 > 0; Keq > 1
ΔG0 < 0; Keq > 1
Explanation:

$E_{cell}^0$ < 0, so it is a non-spontaneous process

ΔG0 = – nFE0 = +ve, so ΔG0 > 0

ΔG0 = – 2.303RT log K

So, K < 1

13958.Which one of the following is incorrect for ideal solution?
ΔGmix = 0
ΔHmix = 0
ΔUmix = 0
ΔP = Pobs – Pcalculated by Raoults law = 0
Explanation:

For ideal solution inter molecular forces are identical so,

ΔHmix = 0, ΔUmix = 0, ΔGmix < O

So, 1st option is incorrect.

13959.The solubility of AgCl (s) with solubility product 1.6 × 10–10 in 0.1 M NaCl solution would be
Zero
1.26 × 10–5 M
1.6 × 10–9 M
1.6 × 10–11 M
Explanation:
AgCl ⇋ Ag+ + Cl

Ag+ is S

Cl is 0.1

Ksp = [Ag+] [Cl]

1.6 × 10–10 = S × 0.1

1.6 × 10–9 = S

13960.Suppose the elements X and Y combine to form two compounds XY2 and X3Y2. When 0.1 mole of XY2 weights 10 g and 0.05 mole of X3Y2 weights 9 g, the atomic weights of X and Y are
30, 20
40, 30
60, 40
20, 30
Explanation:

For XY2     n = $\dfrac{w}{M}$

$0.1 = \dfrac{10}{X + 2Y}$

X + 2Y = 100     .......(1)

For X 3Y2     n = $\dfrac{w}{M}$

$0.05 = \dfrac{9}{3X + 2Y}$

3X + 2Y = 180     .......(2)

Form (1) and (2)

2X = 80

X = 40 and

2Y = 100 – 40 = 60

Y = 30

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