INChO 2008 Chemistry Solution from India Indian National Chemistry Olympiad

11 Pages·2008·0.181 MB·English

by  HBCSE Chemistry Team

Answers to INChO-2008 problems
Question No. 1
Subdivisions
1.1) F -1.6, F  - 1.1,1.3
2 2
1.2) F atom -3.4, F molecule - 3.0,3.2
2
1.3) F : -1.4 F : -1.9
2 2
1.4) 4.15

1.5)

  2p  

2p
2p 2p
  2p  



2p

 
2 s
2s

 

F 
F2 2
1.6) F – 1.0 F  - 0.5
2 2
1.7) F 
2
1.8) I = 18.9 eV I = 15.6 eV
1 2
1.9) I =  I = 
1 2p 2 2p

HBCSE, 2nd February 2008 1
Question No. 2
Subdivisions
2.1) a) Z-5-methyl hex-2-en-1-al
b) Z-2-methyl-1-phenyl hept-1-en-6-yne
2.2) B C

T.S.1

T.S.2
2.3) y
g
r
en Int
e
ee
r
F

product

Reaction Coordinate

2.4) i) E
ii) D
iii) E
2.5) a) iv b) iii c) ii d) v e) i
H
2.6) O
O
H

OO OO

H

O H O
H
CH C C CH
2.7) D. 2 3

O
CH2COOH
E. CO OH F. O
O
O
O
OH
OH

2.8) G. Br CH CH CH CH Br
2 2

Br CH CH CH CH
2 2
H.
Br
HBCSE, 2nd February 2008 2
I. J.
CH Br CH Br
2 2

H R Br H R Br

S R
H Br Br H

CH Br CH Br
2 2

O O O
2.9)
O O

O
O O
K
O
2.10)
O
L

O
Question No. 3
Subdivisions
3.1)
i) aromatic iv) yes
ii) aromatic v) acidic
iii) vi) a)

3.2) I < III < II

COOH COOH
3.3) K L
HO H C O
7 3
NO NO
2 2

COCl OH

M N
N(C H )
H C O 2 5 2
7 3 NO O
2
O
O C OC H
3 7
O C OC H
O 3 7 P N(C H ) NH2
2 5 2
N(C H ) NO
2 5 2 2

HBCSE, 2nd February 2008 3
3.4) B r NO2 Br NO2
O O OMe OMe
Br

+ Br Br
3.5) A. B. C. D.
+
N N

Br
3.6) iv.

Question No. 4
Subdivisions
4.1) 8.17  10-8 bar
4.2) 304 K
4.3) 641.02 K
4.4) Yes the reaction will proceed towards NOCl
4.5) Rate = k [NO]2 [Cl ]
2
4.6) E = 98.82 kJ / mol
a
4.7) Mechanism I and II both are possible.
4.8) Extent of the reaction = 0.1
4.9) Extent of the reaction at completion = 0. 195

Question No. 5
Subdivisions
5.1) a.
5.2) b.
5.3) X  Solid phase
1
X  Solid –Liquid equilibrium phase
2
X  Liquid – Gas equilibrium phase
3
X  Gas Phase
4
HBCSE, 2nd February 2008 4
5.4)

gas
p Liquid –gas
m T0
e equilibrium
T
Liquid

T Solid-liquid
m
equilibrium
solid

Time

5.5) b
5.6) Volume will increase on melting
5.7) Single Phase system called Supercritical Fluid
5.8) c
 
p   p  1 p 
5.9) 1 1 1 2 1
 p  p   p or
1 1 2 1

p  p 
1 2 1

 p / p 
1 1 2

5.10) 56
5.11) a. nA =A
n

[A] n KC
2
b.
C
K  1
D
n C
2

HBCSE, 2nd February 2008 5
Question No. 6
Subdivisions
6.1) P

P P

P

6.2) P (s) + 3 NaOH + 3H O  PH (g) + 3 H PO  Na+
4 2 3 2 2

2
6.3) a. H Na+ H H H
or
P O or H P O P + P
2Na
H O ONa O O O ONa O ONa

b. hypophosphite-reducing agent
phosphate –reducing agent
c. They are reducing agents due to presence of P-H bond and lower oxidation state of P
6.4) Ca (PO ) F + 5H SO  3H PO + 5CaSO + HF
5 4 3 2 4 3 4 4
6.5)
O
O

P
O P
O O or O O O
6.6) O 5P04 Ogs PoPf COaOO. O P O POOP O
O
O
6.7) PCl + O  2Cl PO O
3 2 3
POCl +3EtOH O P(OEt) + 3HCl
3 3
6.8)
3s 3p 3d

Ground
state    

Excited

State     

Cl
Cl

P Cl Or trigonal bipyramidal

Cl
Cl

HBCSE, 2nd February 2008 6
6.9)
3PCl + 3NH Cl (Cl PN) + 12 HCl
5 4 2 3

Cl Cl

P
N N

Cl Cl

P P
Cl Cl
N

HBCSE, 2nd February 2008 7
Question No. 7
Subdivisions
7.1) Co3+ : 3d6 4S0
7.2) A Pink: [Co(NH ) .H O]Cl : Pentaamine aqua cobalt(III)chloride
3 5 2 3

B Purple: [CoCl(NH ) ]Cl : Pentaamine chlorocobalt(III)chloride
3 5 2

7.3) Co3+ = 3d6
3d 4s 4p

   XX XX XX XX XX XX

d2sp3 hybridisation
Octahedral

7.4) a.
e
g


t
2g

Co3+=d6

b. diamagnetic.

[Co(NH ) ]2+ = Co2+ [Co(NH ) ]3+ = Co3+
7.5) 3 6 3 6



    
Loss of electron ea sy

HBCSE, 2nd February 2008 8
NH NH
3 3
7.6) NH Cl
3
Cl Co NH3 Cl Co NH3
Cl Cl

Cl NH
3

Facial Meridional

7.7) Facial isomer - one peak due to ammonia (with all similar environments)

Meridional isomer – two peaks
7.8) Cl O
O O
O Co O Co
O Cl

O O
Cl Cl
Inactive plane of
symmetry Chiral

Question No. 8
Subdivisions
8.1) Fe(s) + 2OH(aq) FeO(s) + H O(l) + 2e
2
Ni O (s) + H O(l) + 2e  2NiO(s) + 2OH(aq)
2 3 2
Fe(s) + Ni O (s)  FeO(s) + 2NiO(s)
2 3
8.2) iii.
8.3) E0 = 0.83633 V
cell
E = 0.80283 V
cell
8.4) Ag(s)+ Fe3+(aq) = Fe2+(aq) + Ag+(aq)

Fe(s) + 2Ag+(aq) = Fe2+(aq) + 2Ag(s)
8.5) K 2.97

[Fe3]0.01

HBCSE, 2nd February 2008 9
Question No. 9
Subdivisions
9.1)
H NCH COOH
2 2
9.2) i) Nylon COOH
ii) H N CH NH + (CH ) COOH
2 2 2 2 6

9.3)
Nature Charge

Peptide
Acidic Basic Neutral Positive Negative Zero

Gly-Leu-Val X X

Leu-Trp-Lys-Gly-Lys X X

Arg-Ser-Val X X

9.4) a) +
HN-CH-COO
3

CH
2

S

S

CH CH CH CH
2 6 5 2 3
+ + +
2H3N-CH-COO + H3N-CH-COO + 2H3N-CH-COO

b) +
HN-CH-COO
3 SH

CH
2 CH
2
S (H) +
2HN-CH-COO
3
S

CH
2

+
HN-CH-COO
3
9.5) i) 4

H O COO
ii)
+
H3N C C NH C H
CH COOCH CH C H
2 3 2 6 5
HBCSE, 2nd February 2008 10