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#### Important Questions Part-III

12th Standard EM

Reg.No. :
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Chemistry

Time : 01:00:00 Hrs
Total Marks : 60

Part - A

60 x 1 = 60
1. Which of the following statements, about the advantage of roasting of sulphide ore before reduction is not true?

(a)

$\Delta { G }_{ f }^{ 0 }$ of sulphide is greater than those for CS2 and H2S

(b)

$\Delta { G }_{ r }^{ 0 }$ is negative for roasting of sulphide ore to oxide

(c)

Roasting of the sulphide to its oxide is thermodynamically feasible

(d)

Carbon and hydrogen are suitable reducing agents for metal sulphides

2. Match items in column - I with the items of column – II and assign the correct code.

 Column-I Column-II A. Cyanide process (i) Ultrapure Ge B Froth floatation process (ii) Dressing of ZnS C Electrolytic reduction (iii) Extraction of Al D Zone refining (iv) Extraction of Au (v) Purification of Ni
(a)
 A B C D
(b)
 A B C D (i) (ii) (iii) (iv)
(c)
 A B C D (iii) (iv) (v) (i)
(d)
 A B C D (ii) (iii) (i) (v)
3. Magnesite is_________

(a)

Magnesium oxide

(b)

Magnesium carbonate

(c)

Magnesium sulphate

(d)

Magnesium chloride

4. The percentage of carbon in high carbon steel is_________

(a)

0.5 - 1%

(b)

0.15 - 1.5%

(c)

0.15 - 1.5%

(d)

0.15 - 0.3%

5. In Hall-Herold process___________act as an, anode.

(a)

Carbon blocks

(b)

hydrogen

(c)

copper rods

(d)

Zinc rods

6. Duralumin is an alloy of

(a)

Cu,Mn

(b)

Cu,Al,Mg

(c)

Al,Mn

(d)

Al,Cu,Mn,Mg

7. Thermodynamically the most stable form of carbon is

(a)

Diamond

(b)

graphite

(c)

Fullerene

(d)

none of these

8. Identify the electron - deficient species

(a)

(BH3)2

(b)

(SiH3)2

(c)

PH3

(d)

(CH3)2

9. Boron compounds behave as Lewis acid, because of their

(a)

ionisation property

(b)

acidic nature

(c)

covalent nature

(d)

electron deficient nature

10. Borax is _______

(a)

Na2[B4O5(OH)4).8H2O

(b)

Na2[B4O5(OH)6).7H2O

(c)

Na2[B4O3(OH)8].6H2O

(d)

Na2[B4O2(OH)10).5H2O

11. In the brown ring test, brown colour of the ring is due to

(a)

a mixture of No and NO2

(b)

Nitroso ferrous sulphate

(c)

Ferrous nitrate

(d)

Ferric nitra

12. The correct order of the thermal stability of hydrogen halide is

(a)

HI > HBr > HCl > HF

(b)

HF > HCl > HBr > HI

(c)

HCl > HF > HBr > HI

(d)

HI > HCl > HF > HBr

13. Allotrope of sulphur which shows paramagnetic behaviour

(a)

S8- Rhombic

(b)

S8- Monoclinic

(c)

S2- In vapour phase

(d)

Not possible

14. Which one of the following orders is not in accordance with the property stated against it?

(a)

F2> CI2> Br2> I2:Bond dissociation energy

(b)

HI > HBr> HCI > HF : Acidic property in water

(c)

F2> Cl2> Br2> l2: Oxidising power

(d)

F2> Cl2> Br2> l2: Electronegativity

15. Strong reducing behaviour of H3PO2 is due to______

(a)

High oxidation state of phosphorus

(b)

High electro gain enthalpy of phosphorus

(c)

Presence of two-OH groups and one P-H bond

(d)

Presence of one-OH groups and two P-H bonds

16. Permanganate ion changes to ________ in acidic medium

(a)

MnO42−

(b)

Mn2+

(c)

Mn3+

(d)

MnO2

17. Which one of the following statements related to lanthanons is incorrect?

(a)

Europium shows +2 oxidation state

(b)

The basicity decreases as the ionic radius decreases from Pr to Lu.

(c)

All the lanthanons are much more reactive than aluminium

(d)

Ce4+ solutions are widely used as oxidising agents in volumetric analysis.

18. CrO3 is coloured due to

(a)

Low l.E

(b)

Crystal defects

(c)

Charge transfer spectra

(d)

Unpaired electrons

19. On oxidation with KMnO4 in acidic medium, SO2 is oxidised to ___________

(a)

SO2

(b)

H2SO4

(c)

SO32-

(d)

H2S

20. In black and white photography, the developed film is fixed by washing with ____________

(a)

Hypo solution

(b)

AgBr solution

(c)

Na2S4O6 solution

(d)

FeC2O4 solution

21. Oxidation state of Iron and the charge on the ligand NO in [Fe(H2O)5NO]SO4 are

(a)

+2 and 0 respectively

(b)

+3 and 0 respectively

(c)

+3 and -1 respectively

(d)

+1 and +1 respectively

22. Which kind of isomerism is possible for a complex<<EVA039.eps>>?

(a)

geometrical and ionization

(b)

geometrical and optical

(c)

optical and ionization

(d)

geometrical only

23. Which is a double salt?

(a)

K2SO4AI2(SO4)324H2O

(b)

NaCI

(c)

K4[Fe(CN)6]

(d)

KCl

24. Pick out the central metal ion in the complex K3[AI(C2O4)3].

(a)

3K+

(b)

Al3+

(c)

C2O42-

(d)

both (a) and (b)

25. [Ni(Co)4] is a_____________ complex.

(a)

anionic

(b)

cationic

(c)

neutral

(d)

ambidentate

26. The radius of an atom is 300pm, if it crystallizes in a face centered cubic lattice, the length oif the edge of the unit cell is

(a)

488.5pm

(b)

848.5pm

(c)

884.5pm

(d)

484.5pm

27. The fraction of total volume occupied by the atoms in a simple cubic is

(a)

$\left( \cfrac { \pi }{ 4\sqrt { 2 } } \right)$

(b)

$\left( \cfrac { \pi }{ 6 } \right)$

(c)

$\left( \cfrac { \pi }{ 4 } \right)$

(d)

$\left( \cfrac { \pi }{ 3\sqrt { 2 } } \right)$

28. Graphite is a good conductor of electricity due to the presence of____________

(a)

Lone pair of electrons

(b)

Free valence electrons

(c)

Cations

(d)

Anions

29. Iodine crystals are __________.

(a)

covalent

(b)

ionic

(c)

metallic

(d)

molecular

30. A cubic crystal has _________ faces.

(a)

2

(b)

4

(c)

6

(d)

8

31. The decomposition of phosphine (PH3) on tungsten at low pressure is a first order reaction. It is because the (NEET)

(a)

rate is proportional to the surface coverage

(b)

rate is inversely proportional to the surface coverage

(c)

rate is independent of the surface coverage

(d)

rate of decomposition is slow

32. In a homogeneous reaction $A\longrightarrow B+C+D$ the initial pressure was P0 and after time t it was P. expression for rate constant in terms of P0, P and t will be

(a)

$k=\left( \cfrac { 2.303 }{ t } \right) log\left( \cfrac { 2{ P }_{ 0 } }{ { 3P }_{ 0 }-P } \right)$

(b)

$k=\left( \cfrac { 2.303 }{ t } \right) log\left( \cfrac { { 2P }_{ 0 } }{ { P }_{ 0 }-P } \right)$

(c)

$k=\left( \cfrac { 2.303 }{ t } \right) log\left( \cfrac { 3{ P }_{ 0 }-P }{ 2P_{ 0 } } \right)$

(d)

$k=\left( \cfrac { 2.303 }{ t } \right) log\left( \cfrac { 2{ P }_{ 0 } }{ { 3P }_{ 0 }-2P } \right)$

33. Which of the following statement is not correct?

(a)

Molecularity of a reaction cannot be fractional

(b)

Molecularity of a reaction cannot be more than three

(c)

Molecularity of a reaction can be zero

(d)

Molecularity is assigned for each elementary step of mechanism.

34. Compound A reacts by first order kineties. At 25oC, the rate constant of the reaction is 0.60 see:'. What is the half life of A?

(a)

1.15 sec

(b)

0.4158 sec

(c)

0.093 sec

(d)

1.29 sec

35. The oxidation of potassium iodide by potassium persulphate as per the rate law, rate k[K2S2O8] [K1]. The order with respect to potassium iodide is, __________

(a)

two

(b)

one

(c)

three

(d)

four

36. What is the pH of the resulting solution when equal volumes of 0.1M NaOH and 0.01M HCl are mixed?

(a)

2.0

(b)

3

(c)

7.0

(d)

12.65

37. Which of the following can act as lowery – Bronsted acid well as base?

(a)

HCl

(b)

SO42−

(c)

HPO42−

(d)

Br-

38. The relationship between degree ofdissociation of a weak acid and its dissociation constant in a very dilute solution is

(a)

Ka2C

(b)

Ka$\frac{α^2C}{(1+α)}$

(c)

Ka$\frac{α^2}{(1+α)C}$

(d)

Ka$\frac{α}{C(1+α)}$

39. pH of buffer depends upon concentration of

(a)

acid (H+)

(b)

Conjugate base (OH-)

(c)

Salt

(d)

acid (H+) and Conjugate base (OH-)

40. NH4OH is a weak base because

(a)

it has low vapour pressure

(b)

it is only partially ionised

(c)

it is completely ionised

(d)

it has low densit

41. Among the following cells
I) Leclanche cell
IV) Mercury cell
Primary cells are

(a)

I and IV

(b)

I and III

(c)

III and IV

(d)

II and III

42. In H2-Ofuel cell the reaction occur at cathode is

(a)

O2(g) + 2H2O (l) + 4e- ⟶ 4OH (aq)

(b)

H+(aq) + OH (aq) ⟶ H2O (l)

(c)

2H2 (g) + O (g) ⟶ 2H2O (g)

(d)

H+ + e-+ ⟶ 1/2 H2

43. Faraday's laws of electrolysis are related to

(a)

atomic number of the cation

(b)

atomic number of the anion

(c)

equivalent weight of the electrolyte

(d)

speed ofthe cation

44. The feasibility of a redox reaction can be predicted with the help of

(a)

Electronegativity

(b)

Electrochemical series

(c)

Electron affinity

(d)

Equivalent conductance

45. 1 F equals to _________

(a)

96500 moles

(b)

96500 C

(c)

1.6 x 10-19 C

(d)

1.6 X 10-19 moles

46. Which of the following is incorrect for physisorption?

(a)

reversible

(b)

increases with increase in temperature

(c)

(d)

increases with increase in surface area

47. On which of the following properties does the coagulating power of an ion depend ?

(a)

Both magnitude and sign of the charge on the ion.

(b)

Size of the ion alone

(c)

the magnitude of the charge on the ion alone

(d)

the sign of charge on the ion alone.

48. The phenomenon of Tyndall's effect is not observed in

(a)

emulsion

(b)

colloidal solution

(c)

true solution

(d)

none

49. A substance that enhances the catalytic activity of the catalyst is

(a)

gel

(b)

sol

(c)

promoter

(d)

poison

50. The decomposition of hydrogen peroxide in the presence of colloidal platinum is a/an

(a)

positivecatalysis

(b)

negativecatalysis

(c)

auto-catalysis

(d)

induced catalysis

51. on treatment with Con H2SO4, predominately gives

(a)

(b)

(c)

(d)

52. Carbolic acid is

(a)

Phenol

(b)

Picri cacid

(c)

benzoic acid

(d)

phenylacetic acid

53. Which is optically active?

(a)

n-butyl alcohol

(b)

isobutyl alcohol

(c)

2-butanol

(d)

t-butyl alcohol

54. The compound that acts as a solvent for Grignard reagent is :

(a)

Ethyl alcohol

(b)

Diethyl ether

(c)

Acetone

(d)

Benzene

55. In swern method of oxidation of alcohols to aldhedye/ ketones _______ is used as an oxidising agent.

(a)

dimethyl sulfoxide

(b)

pyridimium chloro chromate

(c)

CrO3 in anhydrousmedium

(d)

Na2Cr2O7 |H+

56. Ethanoic acid $\overset { P/{ Br }_{ 2 } }{ \longrightarrow . }$2-bromoethanoic acid. This reaction is called

(a)

Finkelstein reaction

(b)

Haloform reaction

(c)

Hell – Volhard – Zelinsky reaction

(d)

none of these

57. An alkene “A” on reaction with O3 and Zn - H2O gives propanone and ethanol in equimolar ratio. Addition of HCl to alkene “A” gives “B” as the major product. The structure of product “B” is

(a)

$Cl-{ CH }_{ 2 }-CH_{ 2 }-\overset { \overset { CH_{ 3 } }{ | } }{ \underset { \underset { CH_{ 3 } }{ | } }{ CH } }$

(b)

${ H }_{ 3 }C-{ CH }_{ 2 }-\overset { \overset { CH_{ 2 }Cl }{ | } }{ CH } -{ CH }_{ 3 }$

(c)

$\\ { H }_{ 3 }C-{ CH }_{ 2 }-\overset { \overset { CH_{ 3 } }{ | } }{ \underset { \underset { CH_{ 3 } }{ | } }{ C } } -{ CH }_{ 3 }$

(d)

${ H }_{ 3 }C-{ CH }-\overset { \overset { CH_{ 3 } }{ | } }{ \underset { \underset { Cl }{ | } }{ C } }$

58. Which of the following acids do not exhibit optical isomerism?

(a)

lactic acid

(b)

tartaric acid

(c)

maleic acid

(d)

both (a) and (b)

59. Which of the following does not give iodoform test?

(a)

aceto phenone

(b)

benzophenone

(c)

${ CH }_{ 3 }-\underset { \overset { | }{ { CH }_{ 3 } } }{ CHOH }$

(d)

${ CH }_{ 3 }-\underset { \overset { | }{ OH } }{ CH } -{ { CH }_{ 2 }{ CH }_{ 2 }-CH }_{ 3 }$

60. Bakelite is a product of reaction between

(a)

formaldehyde and NaOH

(b)

phenol and methanal

(c)

aniline and NaOH

(d)

aniline and NaOH

61. Part - B

40 x 2 = 80
62. Which type of ores can be concentrated by froth floatation method? Give two examples for such ores.

63. Out of coke and CO, which is better reducing agent for the reduction of ZnO? Why?

64. The reaction
${ Cr }_{ 2 }{ O }_{ 3 }+2{ Al }_{ (s) }\longrightarrow { Al }_{ 2 }O_{ 3 }+2Cr$
$\Delta { G }^{ 0 }=-421KJ$ is thermodynamically feasible why does it not take place at room temperature?

65. Define roasting,

66. Write a short note on anamolous properties of the first element of p-block

67. What is catenation ? describe briefly the catenation property of carbon

68. Give the uses of alum.

69. Which one is more soluble in diethyl ether, anhydrous Alcl3 or hydrated Alcl3? Explain in terms of bonding.

70. What is inert pair effect?

71. Give the uses of helium.

72. What is the reaction of Phosphorous with alkali?

73. Elements of group 16 show lower value of first ionization enthalpy compared to group 15, why?

74. What are inner transition elements?

75. Why Gd3+ is colourles?

76. Silver atom has completely filled d-orbitals (4d10) in its ground state. How can you say that it is a transition element?

77. Draw the structure of permanganate ion.

78. Arrange the following in order of increasing molar conductivity
(i) Mg[Cr(NH3)(Cl)5]
(ii) Cr(NH3)5Cl]3[CoF6]2
(iii) [Cr(NH3)3Cl3]

79. Based on VB theory explain why [Cr(NH3)6]3+ is paramagnetic, while [Ni(CN)4]2- is diamagnetic.

80. Give the geometry and magnetic character of [NiCI4]2-

81. What are structural isomers?

82. Why do solids have a definite volume?

83. Write a note on the assignment of atoms per unit cell in body centred cubic lattice or CsCl.

84. Define half life of a reaction. Show that for a first order reaction half life is independent of initial concentration

85. Rate of chemical reaction is not uniform throughout. Justify you answer:

86. For a chemical reaction, Variation in the concentration In[A] Vs time in seconds is given as

(i) What is the order of the reaction?
(ii) What is the unit of rate constant K?
(iii) Give the relationship between k and ${ t }_{ \frac { 1 }{ 2 } }$

87. The rate of the reaction X+2y⇾ product is 4x10-3 mol L-1S-1, if [X]=[Y]=0.2M and rate constant at 400K is 2x10-2s-1, What is the overall order of the reaction

88. A lab assistant prepared a solution by adding a calculated quantity of HCl gas 250C o to get a solution with [H3O+]= 4$\times$10-5M. Is the solution neutral (or) acidic (or) basic.

89. Calculate the pH of 0.001M HCl solution

90. Write down the conjugate acid and base of the following
(i) NH3
(ii) HSO-4

91. BF3 is termed as an acid though it does not contain H+ ions. Explain.

92. State Kohlrausch Law. How is it useful to determine the molar conductivity of weak electrolyte at infinite dilution.

93. Calculate the molar conductance of 0.025M aqueous solution of calcium chloride at
25°C. The specific conductance of calcium chloride is 12.04 × 10-2 Sm-1.

94. On dilution of 0.1 M of Na2SO4, what will happen to its
a) Conductance (C)
(b) Conductivity K
(c) Molar conductance Am
(d) Equivalent conductance ${ \Lambda }_{ m }$

95. What is corrosion?

96. What is a dispersed phase and a dispersion I medium in a colloid?

97. What is electrophoresis?

98. Identify the product A and B.

99. Write the IUPAC names of
(i) CH3OCH2CH2O
(ii) CH3OCH2OCH3 and
(iii)

100. What is urotropine? Give its use.

101. Identify (B)(C) and (D)
${ CH }_{ 3 }-\overset { \underset { || }{ O } }{ C } -{ CH }_{ 3 }-(A)\overset { LIAIH_{ 4 } }{ \longrightarrow } (B)\overset { { SOCl }_{ 2 } }{ \longrightarrow } (C)\overset { alc.KOH }{ \longrightarrow } (D)$

102. Part - C

22 x 3 = 66
103. (A) Predict the conditions under which
(i) Aluminium might be expected to reduce magnesia.
(ii) Magnesium could reduce alumina.
(B) Carbon monoxide is more effective reducing agent than carbon below 983K but, above this temperature, the reverse is true –Explain.
(c) it is possible to reduce Fe2O3 by coke at a temperature around 1200K

104. Mention the uses of copper

105. Write a short note on hydroboration

106. How is boron trifluoride obtained from boron trioxide?

107. Write the molecular formula and structural formula for the following molecules.
a) Nitric acid
b) dinitrogen pentoxide
c) phosphoric acid
d) phosphine

108. Explain the structure of ammonia

109. What are interstitial compounds?

110. Discuss the general characteristic of the 3d series of the transition elements with special reference to their
(i) Atomic size
(ii) Enthalpies of atomisation

111. [Ni(CN)4]2- is diamagnetic, while [NiCl4]2- is paramagnetic , explain using crystal field theory.

112. Explain optical isomerism.

113. How do the spacings of the three planes (100), (101) and (111) of simple cubic lattice vary?

114. The decomposition of NH3 on platinum surface is zero order reaction what are the rates of production of N2 and H2 if k = 2.5 X 10-4 mol+ L S-1.

115. Show that in case of first order reaction, the time required for 99.9% completion is nearly ten times the time required for half completion of the reaction.

116. The Ka value for HCN is 10-9 . What is the pH of 0.4M HCN solution?

117. Based on Arrhenius concept, defme acid and bases and give an example for each.

118. A solution of silver nitrate is electrolysed for 20 minutes with a current of 2 amperes. Calculate the mass of silver deposited at the cathode.

119. Explain the process of recharging of lead storage battery.

120. Why are lyophillic colloidal sols are more stable than lyophobilc colloidal sol.

121. Give any three application of adsorption.

122. How do primary, secondary and tertiary alcohols differ in terms of their oxidation?

123. When tertiary butyl alcohol and 1-butanol are separately treated with a few drops of KMnO4, in one case only the purple colour disappears and a brown precipitate is formed. Which of the two alcohols gives the above reaction and what is that brown precipitate?

124. Explain Stephen's reaction.

125. Part - D

12 x 5 = 60
126. How can you separate alumina from silica in a bauxite ore

127. Distinguish between diamond and graphite.

128. An element A occupies group number IS and period number 3, exhibits allotropy and it is tetra atomic. A reacts with caustic soda to give B which is having rotten fish odour. A reacts with chlorine to give C which has a pungent odour Identify A, Band C. Write the reactions.

129. Why is there a variation of atomic andionic size as we move from Sc to Zn?

130. Give the IUPAC name for the following compounds.
(i) [Ag(NH3)2]CI
(ii) K3[Fe(CN)5NO]
(ill) [Cr(PPh3)(CO)3]
(iv) [Ag(NH3)2]+
(v) [FeF6]4-

131. Ionic solids, which have anionic vacancies due to metal excess defect, develop colour. Explain with the help of a suitable example.

132. A first order reaction laws on rate constant 1.15 x 10-3 S-1. How long will 5 g of this reactant take to reduce to 3g?

133. Calculate the pH of solution with HO+ concentrations in mol dm-3.
(i) 10-4
(ii) 10-7
(iii) 6.8 x 10-3
(iv) 3.2 x 10-5
(v) 0.035
(vi) 0.25
(vii) 5.4 x 10-9
(viii) 7.1 x 10-7

134. Calculate the emf of the cell having the cell reaction 2Ag+ + Zn ⇌ 2Ag + Zn2+ and Eocell= 1.56 V at 25°C when concentration of Zn2+ = 0.1 M and Ag+ = 10 M in the solution.
$[{ E }_{ cell }={ E }_{ cell }^{ o }-\frac { RT }{ nF } In\frac { [{ Zn }^{ 2+ }] }{ [{ Ag] }^{ 2 } } ]$

135. Write a note on Freundlich adsorption isotherm.

136. Distinguish between (a) Ethanol and phenol (b) Phenol and acetic acid (c) Phenol and aniline (d) Phenol and anisole.

137. An organic compound A (C7H6O) forms a bisulphite. A when treated with alcoholic KCN forms B (C14H12O2) and A on refluxing with sodium acetate and acetic anhydride forms an add C (C9HsO2). Identify A, B and C. Explain the conversion of A to Band C.