PAPER – III

 

 

61. The value of the Vander Waal’s constant ‘a’ for the gases O₂, N₂, NH₃ and CH₄ are 1.36, 1.39, 4.17 and 2.253 unit respectively. The gas which can be liquefied most easily is

(A) O₂                                                              (B) N₂

(C) NH₃                                                           (D) CH₄

 

62. Number of atoms of calcium that will be deposited from a solution of CaCl₂ by a current of 25 mA for 60 seconds will be

(A) 4.68 ´ 10¹⁸                                                (B) 4.68 ´ 10¹⁵

(C) 4.68 ´ 10¹⁰                                                (D) 2.34 ´ 10¹⁵

 

63. Acetophenone on reaction with p-nitroperbenzoic acid gives

(A) phenyl propionate                                     (B) phenyl acetate

(C) methyl benzoate                                       (D) Benzophenone

 

64. For reaction A ® B 80% A is decomposed in 1 hr. 96% is decomposed in 2 hrs. 99.2% is decomposed in 3 hrs. 99.84% is decomposed in 4 hours. What is the order of the reaction?

(A) Zero                                                           (B) 1^st

(C) 2^nd                                                             (D) can not be predicted

 

65. Which carbanion is most stable

(A) Me₃C^–                                                       (B) Ph₃C^–

(C) ^–CH₃                                                          (D)

 

66. CsCl crystallises in an ideal bcc manner (Cs⁺ at the centre and Cl^– at the corners of unit cell). If the ionic radius of Cl^– is 1.5Å, the ionic radius of Cs⁺ will be

(A) 0.549Å                                                       (B) 2.196 Å

(C) 1.896 Å                                                      (D) 1.098 Å

 

67. The pH of a solution obtained by mixing 50 ml of 0.4 M HCl and 50 ml of 0.2 M NaOH would be

(A) 1                                                                (B) 3

(C) 4                                                                (D) 2

 

68. An excess of AgNO₃ is added to 100 ml of a 0.01M solution of dichlorotetraaquachromium (III) chloride. The number of moles of AgCl precipitated would be

(A) 0.001                                                         (B) 0.002

(C) 0.003                                                         (D) 0.01

 

69. The emf of the standard cell Zn/Zn⁺⁺|| Ag⁺ /Ag is 1.56 V. If the standard oxidation potential of Zn is 0.76 V the standard reduction potential of Ag is

(A) 2.32 V                                                        (B) 0.8 V

(C) –2.32 V                                                      (D) – 0.8 V

 

70. In a basic solution oxidises  to form  & . How many millilitres of 0.154 M Na₂CrO₄ are required to react with 40 ml of 0.246 M Na₂S₂O₃?

(A) 240.2 ml                                                    (B) 120 ml

(C) 10.2 ml                                                      (D) 170.4 ml

 

71. Markownikoff addition of HBr is observed in

(A) propene                                                     (B) but -2-ene

(C) Hex-3-ene                                                 (D) pent-2-ene

 

72. Acetic acid and propionic acid have K_a values 1.75 ´ 10^-5 and 1.3 ´ 10^-5 respectively at a certain temperature. An equimolar solution of a mixture of the two acids is partially neutralised by NaOH. How is the ratio of the contents of acetate and propionate ions related to the K_a values and the molarity?

(A) ,0 where a and b are ionised fractions of the acids

(B) The ratio is unrelated to the K_a    values

(C) The ratio is unrelated to the molarity

(D) The ratio is unrelated to the pH of the solution.

 

73. The ionisation constant of in water is 5.6 ´ 10^–10 at 25^oC. The rate constant for the reaction of  and OH^–  to form NH₃ and H₂O at 25^oC is 3.4 ´ 10¹⁰ L mol^–1 s^–1. The rate constant for proton transfer from water to NH₃ is

(A) 6.07 ´ 10⁵ s^–1                                            (B) 6.07 ´ 10^–10 s^–1

(C) 6.07 ´ 10^–5 s^–1                                          (D) 6.07 ´ 10¹⁰ s^–1

 

74. A drop of solution (volume 0.05 ml) contains 3 ´ 10^–6 moles of H⁺. If the rate constant of disappearance of H⁺ is 1 ´ 10⁷ mole litre^–1 sec^–1.  How long would it take for H⁺ in drop to disappear.

(A) 6 ´ 10^–8 sec                                              (B) 6 ´ 10^–7 sec

(C) 6 ´ 10^–9 sec                                              (D) 6 ´ 10^–10 sec

 

75. Which of the following molecules is not square planar?

(A) Ni(CO)₄                                                     (B) Ni(CN)₄^2–

(C) Pt(CO)₄²⁺                                                  (D) Pt(CN)₄^2–

 

76. Which of the following complex is not paramagnetic?

(A) Fe(CN)₆^4–                                                 (B) Fe(H₂O)₆²⁺

(C) FeF₆^3–                                                       (D) Fe(CN)₆^3–

 

77. Which of the following compound is least basic?

(A) (SiH₃)₃N                                                    (B) Me₃N

(C) NH₃                                                           (D) N₃H

 

78. A partially dried clay mineral contains 8% water. The original sample contained 12% water and 45% silica. The % of silica in the partially dried sample is nearly.

(A) 50%                                                           (B)  49%

(C)  55%                                                          (D)  47%

 

79. A sample of peanut oil weighing 1.5763 g is added to 25 ml of 0.4210 M KOH after saponification is complete 8.46 ml of 0.2732 M H₂SO₄ is headed to neutralize excess KOH. The saponifcation number of peanut oil is

(A) 209.6                                                         (B) 108.9

(C) 98.9                                                           (D) 218.9

 

80. Addition of HCl on 1, 3 butadiene gives

(A)                            (B) H₃C – CH₂ – – CH₃

(C) H₂C = CH – – CH₃                            (D) gives all products shown above

 

 

 

 

81. Which of the following is most acidic?

(A)		(B)
(C)		(D)

 

82. Which of the following is/are optically active?

(A)		(B)
(C)		(D)

 

83. Anti Markownikoff’s addition takes place in following

(A)		(B)
(C)		(D)

 

84. Which of the following molecule having maximum dipole moment?

(A)		(B)
(C)		(D)

 

85. Which of the following compounds doesn’t give Diel’s Alder reaction?

(A)		(B)
(C)		(D)

86. Rate of S_N1 reaction would be maximum for

(A)		(B)
(C)		(D)

 

87.
(A)			(B)
(C)			(D)

 

88.
(A)			(B)
(C)			(D)

 

89. CH₃CH₂CHO A, A is

(A)	CH3CH2CH=CHCH2CHO	(B)
(C)		(D)

 

90.

(A) Can be oxidized by Tollen’s Reagent       (B) Cannot be oxidized by Tollen’s Reagent

(C) Can only be oxidized by CrO₃                  (D) None

 

 

 

Answers

 

61. C                                         

.                 62.       A                                          63.       B                                          64.       B        

65. D                                          66.       D                                          67.       A        
66. 68. A                                                 B                                          70.       D        
67. A                                          72.       A                                          73.       A        
68. C                                          75.       A                                          76.       A        
69. A                                          78.       D                                          79.       A        
70. A                                          81.       B                                          82.       D        
71. 83. C                                          84.       D                                                 D        
72. B                                          87.       A                                          88.       C        
73. A                                          90.       A

 

 

Hints & solutions

 

61. Higher the value of Vander waal’s constant ‘a’ higher will be the force of attraction between the gaseous molecules.

 

62. Charge carried by 1 mole of electron = 96500 coulomb

\ 25 ´ 10^–3 ´ 60 coulombs of charge carried by   = 1.55 ´ 10^–5 mol of electron

Ca²⁺ + 2e ¾® Ca

2 mol of electrons will produce 6.023 ´ 10²³ atoms of Ca.

1.55 ´ 10^–5 mol of electrons will produce

= 4.68 ´ 10¹⁸ atoms Ca

 

63. It is an example of Bayer Villeger oxidation. Here phenyl group migrates because of higher migratory aptitude resulting in phenyl acetate.

 

64. Suppose the reaction is Ist order

So K =

K =

K =

K =

K is same for all reaction. So it is Ist order

 

65. Due to the steric factor all the phenyl rings become out of plane and PhC^‑– is unstable as negative charge cannot delocalise into the phenyl rings.

 

Putting the values and on solving

= 1.098 Å

 

67. Millimoles of HCl added = 50 ´ 0.4  = 20

 

Millimoles of NaOH added  = 50 ´ 0.2  = 10

Molarity of HCl  left  =  = 0.1

pH = 1

 

68. [CrCl₂(H­_2­O)₄]Cl

When AgNO₃ is added Cl present in the ionisation sphere forms precipitate. Since only one chloride is outside the coordination sphere \ when  100 ml of  0.01M i.e., 1 millimole (i.e,) 0.001 mole of AgNO₃ is added, 0.001 mole of AgCl will be precipitated.

 

69. = 1.56 =

\  = 1.56 – 0.76  = 0.8 V

 

\ meq. of Na₂CrO₄ -= meq. of Na₂S₂O₃

0.154 ´  3 ´ V = 40 ´ 0.246 ´ 8

\ V = 170.4 ml

 

71. Anti – Markownikoff addition of HBr is observed in non – symmetrical alkenes. Except propene all are non symmetrical

 

72. In a given mixture, the ionisation of two acid can be written as: Let a, b be degree of ionisation at same concentration.

CH₃COOH  CH₃COO^– + H⁺

1 – a                            a         a + b

C₂H₅COOH  C₂H₅COO^– + H⁺

1 – b                            b             a + b

\ K_A×A =

K_P×A =

 

 

 

73. NH₃ + H₂O NH₄⁺+ OH^–; K_b = 3.4 ´ 10¹⁰

NH₄⁺ + H₂O  NH₄OH + H⁺; K_a = 5.6 ´ 10¹⁰

K_base NH₃ = (Q K­_acid ´ K_base = K_w)

or

or K_f = 6.07 ´ 10⁵

 

74. Since rate constant = 1.0 ´ 10⁷ mol litre^–1 sec

\ Zero order reaction

For zero order reaction t =             …(I)

Q 0.05 mL has 3 ´ 10^–6 moles of H⁺

\ 1000 mL has  = 0.6 ´ 10^–1 mol/litre

\ By equation (1) t =  = 6 ´ 10^–9 sec

 

75. Ni(CO)₄ is tetrahedral as here oxidation no. of ‘Ni’ is zero.

 

77. Due to presence of vacant ‘d’ orbital of ‘Si’ the lone pair of nitrogen atom makes p-bond and it is not available for donation.

 

78. Silica Water                          Clay mineral

45  12                          43                                43 initial %

a                                  8                                  92 – a % after heating

The % ratio of silica that clay remains constant on heating

i.e.

a = 47%

 

79. Meq. of KOH added = 25 ´ 0.4210 = 10.525

Meq. of KOH left = 8.46 ´ 0.2732 ´ 2 = 4.623

\ Meq. of KOH used by oil = 10.525 – 4.623 = 5.902

or  = 5.902

or W_KOH = 0.3305 g

\ Saponification no. = Wt. Of KOH used in mg/g of oil

=  = 209.6

 

80. The reaction is passing through allylic carbocation formaiton.

 

81. Due to –I effect of – NO₂ group negative charge on oxygen can easily be delocalised into the ring. But in option (D) due to steric factor motrp – NO₂ group becomes out of plane.

 

82.

does not contains any plane of symmetry.  But other compounds contain plane of symmetry.

 

83. Due to the –I effect of –CF₃ and –NO_2­ here primary carbocation is more stable than secondary carbocation.

 

84. To gain aromaticity the molecule exists into charge separated form

 

 

85. Due to loss of aromaticity benzene does not give D.A. reaction.

 

86. Most stable carbocation is Me₃C⁺.

 

87. Aldol condensation passes through more stable enol form.

 

88. Here ring contraction takes place during Pinacol Pinacolone rearrangement.

 

89. In aldol condensation a-hydrogens are removed, and then form the aldol which is followed by dehydration

 

90. CH₃ –– group also can be oxidised by Tollen’s reagent