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Chemistry 2008

36. At , the vapour pressure of pure liquid ‘A’ is 520 mm. Hg and that of pure liquid ‘B’ is 1000 mm Hg. If a mixture solution of ‘A’ and ‘B’ boils at and I atm pressure, the amount of ‘A’ in the mixture is (1 atm = 760 mm Hg)

(1) 50 mol percent

(2) 52 mol percent

(3) 34 mol percent

(4) 48 mol percent

Ans.

(solution boils when its pressure becomes 1 atom =760 mm Hg)

X_B = 1 - X_A

=> X_A = 1/2 => 50 mol percent

37 For a reaction , rate of disappearance of ‘A’ is related to the rate appearance of ‘B’ by the expression

Ans.

38 The equilibrium constants and for the reactions X 2Y and Z P + Q, respectively are in the ratio of 1: 9. If the degree of dissociation of X and Z be equal then the ratio of total pressures at these equilibria is

(1) 1 : 9

(2) 1 : 36

(3) 1 : 1

(4) 1 : 3

Ans (2)

39 Oxidising power of chlorine in acqueous solution can be determined by the parameters indicated below:

The energy involved in the conversion of

(using the data,

will be

(1) +120 kJ mol^-1

(2) +152 kJ mol^-1

(3) - 610 kJ mol^-1

(4) - 850 kJ mol^-1

Ans(3)

40 a- D –(+) glucose and b-D- (+) – glucose are

(1) Enantiomers

(2) Conformers

(3) Epimers

(4) Anomers

Ans.(4)

a-form & b-form are known as anomers

41 The absolute configuration of

(1) S, R

(2) S, S

(3) R, R

(4) R, S

Ans(3)

Note: we should view from the opposite side of priority (4) group => R, R

42 Which of the following factors is of no significance for roasting sulphide ores to the oxides and not subjecting the sulphide ores to carbon reduction directly?

(1) CO₂is more volatile than CS₂

(2) Metal sulphides are thermodynamically more stable than CS₂

(3) CO₂ is thermodynamically more stable than CS₂

(4) Metal sulphides are less stable than the corresponding oxides

43 The electrophile, E^q attacks the benzene ring to generate the intermediate s- complex, Of the following, which s- complex is of lowest energy?

Ans(3)

[ Due to resonance stabilization of +ve charge]

hence, this structure is of least energy

[ This structure is of height energy since NO₂ being –EWG destabilizes +ve charge directly]

Note: other 2 structures are also of higher energy due to the some reason above.

44 Bakelite is obtained from phenol by reacting with

(1) HCHO

(2) (CH₂OH)₂

(3) CH₃CHO

(4) CH₃COCH₃

_Ans(1)

45 The organic chloro compound, which shows complete stereochemical inversion during a S_N2 reaction, is

(1) CH₃Cl

(2) (C₂H₅)₂CHCl

(3) (CH₃)₃CCl

(4) (CH₃)₂CHCl

Ans(A)

SN₂ reaction occur with primary alkyl halides with complete stereochamical (walder) inversion.

46 Toluene is nitrated and the resulting product is reduced with tin and hydrochloric acid. The product so obtained is diazotised and then heated with cuprous bromide. The reaction mixture so formed contains

(1) Mixture of o^- and m-bromotoluenes

(2) Mixture of o^- and p-bromotoluenes

(3) Mixture of o^- and p-dibromobenzenes

(4) Mixture of o^- and p-bromoanilines

Ans(B)

Note: O-product will also be formed

47 In the following sequence of reactions, the alkene affords the compound ‘B’

The compound B is

(1) CH₃CHO

(2) CH₃CH₂CHO

(3) CH₃COCH₃

(4) CH₃CH₂COCH₃

_Ans(1)

48 For the following three reactions a, b and c, equilibrium constants are given:

Which of the following relations is correct?

Ans(4)

49 Standard entropy of X₂, Y₂ and XY₃ are 60, 40 and 50 J K^-1 mol^-1, respectively. For the reaction,

to be at equilibrium, the temperature will be

(1) 1000 K

(2) 1250 K

(3) 500 K

(4) 750 K

Ans(4)

50 Phenol, when it first reacts with concentrated sulphuric acid and then with concentrated nitric acid, gives

1. nitrobenzene

2. 2, 4, 6-trinitrobenzene

3. o-nitrophenol

4 p-nitrophenol

Ans

None of the choice is correct

51 The hydrocarbon which can react with sodium in liquid ammonia is

1. CH₃CH₂C = CCH₂CH₃

2. CH₃CH₂CH₂C = CCH₂CH₃

3. CH₃CH₂C = CH

4 CH₃CH = CHCH₃

_Ans(3)

Only terminal alkynes react with Na in liq. NH₃ to give sodium acetylides.

52 The treatment of CH₃MgX with CH₃C= C-H produces

Ans(A)

53 The correct decreasing order of priority for the functional groups of organic compounds in the IUPAC system of nomenclature is

1. -CONH₂, -CHO, -SO₃H, -COOH

2. -COOH, -SO₃H, -CONH₂, -CHO

3. -SO₃H, -COOH, -CONH₂ -CHO

4 -CHO, -COOH, -SO₃H, -CONH₂

_Ans(3)

Order of preference is

54 The pK_a of a week acid, HA is 4.80. The pK_b of a week base, BOH, is 4.78. The pH of an aqueous solution of the corresponding salt, BA, will be

1. 9.22

2. 9.58

3. 4.79

4 7.01

Ans(4)

55 In context with the industrial preparation of hydrogen from water gas (CO + H₂), which of the following is the correct statement?

1. CO is oxidised to CO₂ with steam in the presence of a catalyst followed by absorption of CO₂ in alkali

2. CO and H₂ are fractionally separated using differences in their densities

3. CO is removed by absorption in aqueous Cu₂CI₂ solution

4 H₂ is removed through occlusion with Pd

Ans(1)

56 In a compound, atoms of element Y form ccp lattice and those of element X occupy 2/3^rd of tetrahedral voids. The formula of the compound will be

1. X₃Y₄

2. X₄Y₃

3. X₂Y₃

4 X₂Y

Ans(2)

No. of Y atom = 4 (due to CCP)

No. of tetrahedral voids in FCC = 8

No. of tetrahedral voids occupied by X = 2/3*8=16/3

57 Which one of the following pairs of species has the same bond order?

1. NO⁺ and CN⁺

2. CN^-and NO⁺

3 CN^-and CN⁺

4 O₂^-and CN^-

^Ans(2)

Look for total number of electrons:

NO⁺ : 14

CN^- : 14

CN⁺ : 12

O₂- : 17

58 The vapour pressure of water at 20^oC is 17.5 mm Hg. If 18 g of glucose (C₆H₁₂O₆) is added to 178.2 g of water at 20^oC, the vapour pressure of the resulting solution will be

1. 17.325 mm Hg

2. 17.675 mm Hg

3. 15.750 mm Hg

4 16.500 mm Hg

Ans(1)

59 Four species are listed below :

(i) HCO₃^-

(ii) H₃O⁺

(iii) HCO₄^-

(iv) HSO₃F

Which one of the following is the correct sequence of their acid strength?

1. iii < i< iv < ii

2. iv < ii < iii < i

3. ii < iii < i < iv

4 i < iii< ii< iv

Ans(4)

Look at the PK_a values:

HCO₃^- : 10.25

H₃O⁺: -1.74

HCO₄^-: 1.92

HSO₃F : (super acid)

HCO₄^-: 1.92

HSO₃F : (super acid)

60 The ionization enthalpy of hydrogen atom is 1.312 X10⁶ J mol^-1. The energy required to excite the electron in the atom from n =1 to n = 2 is

1. 9.84 X10⁵ J mol^-1

2. 8.51 X10⁵ J mol^-1

3. 6.56 X10⁵ J mol^-1

4 7.56 X10⁵ J mol^-1

Ans(1)

61 Which one of the following constitutes a group of the isoelectronic species?

Ans(3)

Isolectronic species same electronic configuration (same no of e^- s)

N₂: 14

O₂^2-: 17

NO⁺: 14

CO: 14

NO: 13

C₂^2-:14

O₂^2-: 18

CN^-: 14

62 Gold numbers of protective colloids A, B, C and D are 0.50, 0.01, 0.10 and 0.005 respectively. The correct order of their protective powers is

1. B < D < A < C

2. D < A < C < B

3. C < B < D < A

4 A < C < B < D

Ans(D)

63 Larger number of oxidation states are exhibited by the actinoids than those by the lanthanoids, the main reason being

1. more reactive nature of the actinoids than the lanthanoids

2. 4f orbitals more diffused than the 5f orbitals

3. lesser energy difference between 5f and 6d than between 4f and 5d orbitals

4 more energy difference between 5f and 6d than between 4f and 5d orbitals.

Ans(C)

Due to lesser energy difference between 5f & 6d, larger oxidation station of actinoids are possible

64 Given

The potential for the cell

Cr | Cr³+ (0.1M) || Fe²+ (0.01 M) | Fe is

1. -0.26 V

2. 0.26 V

3. 0.339 V

4. -0.339 V

Ans(B)

65 Amount of oxalic acid present in a solution can be determined by its titration with KMnO₄ solution in the presence of H₂SO₄. The titration gives unsatisfactory results when carried out in the presence of HCI, because HCI

1. oxidises oxalic acid to carbon dioxide and water

2. gets oxidised by oxalic acid to chlorine

3. furnishes H⁺ ions in addition to those from oxalic acid

4 reduces permanganate to Mn²⁺

^Ans(4)

MnO₄^- oxidizes HCl to Cl₂

66 Among the following substituted silanes the one which will give rise to cross linked silicone polymer on hydrolysis is

1. R₃SiCI

2. R₄Si

3. RSiCI₃

4 R₂SiCI₂

_Ans(D)

Commercial silicon polymers are synthesized by the hydrolysis of 1 R₂SiCl₂ [RºMe or Ph ]

67 In which of the following octahedral complexes of Co (at no. 27), will the magnitude of D₀be the highest?

1. [Co(NH₃)₆]³⁺

2. [Co(CN)₆]^3-

3. [Co(C₂O₄)₃]^3-

4 [Co(H₂0)₆]³⁺

^Ans(2)

CN^- is the strongest ligand out of –NH₃, C₂O₄^2- H₂O thus D₀ will be higest for [CO(CN)₆]^3-

68 The coordination number and the oxidation state of the element ‘E’ in the complex [E(en)₂ (C₂O₄)]NO₂ (where (en) is ethylene diamine) are, respectively,

1. 6 and 3

2. 6 and 2

3. 4 and 2

4 4 and 3

Ans(1)