microsoft word - chemistry conceptual and important questions for cbse

8/8/2019 Microsoft Word - Chemistry Conceptual and Important Questions for CBSE

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DPS MIS DOHA QATAR [email protected]

Assignment- I / Important questions Mr. S Gul Hasan

Students have to write the answers in the space provided; no separate sheet should be used.

PART I Organic Chemistry

Q. 1. Among the isomeric alkanes of molecular formula C5H12, identify the

one that on photochemical chlorination yields (i) A single monochloride (ii)

Three isomeric monochlorides. (1 mark)

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Q. 2. While separating a mixture of ortho and para nitrophenols by steam

distillation, name the isomer which will be steam volatile. Give reason. (1 mark)

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Q. 3. Write the IUPAC name of the following. (2 mark)

(i) (ii) (iii) (iv)


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Q. 8.Account for the following. (3 marks)

a. It is necessary to avoid even traces of moisture from aGrignard reagent.

b. Chloroform is stored in closed dark coloured bottlescompletely filled.

c. The carbon oxygen bond length in phenol is slightlyless than that in methanol.

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Q. 9. (a) Explain the fact that in aryl alkyl ethers (i) the alkoxy group activates

the benzene ring towards electrophilic substitution and

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(ii) it directs the incoming substituents to ortho and para positions in benzene

ring. (2 mark)

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(b) Arrange the following compounds in increasing order of their acid strength:

(1 mark)

Propan-1-ol, 2,4,6-trinitrophenol, 3-nitrophenol, 3,5-dinitrophenol, phenol,4-methylphenol

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Q. 10. Give equations of the following reactions: (3 mark)

a. Preparation of Sec-Butyl alcohol from ethanalb. Preparation of Phenol from Aniline.c. Treating phenol with chloroform in presence of aqueous

NaOH.

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Q. 11. How will you distinguish between the following: (3 marks)

a. Propanoic acid and propanalb. Ethanal and Benzaldehydec. Pentan-3-one and Pentan-2-one

Compound Propanoic acid propanal

Test

Compound Ethanal Benzaldehyde

Compound Pentan-3-one Pentan-2-one

Q. 12. How will you bring about the following conversions in not more than

two steps. (5 marks)

a. Propanone to Propeneb. Benzene to m-Nitroacetophenonec. Chlorobenzene tobenzoic acidd. Propanoic acid to propenee. Propyne to propan-2-ol


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Q. 13. Explain the following with the help of suitable examples: (5 marks)

(a) Limitation of Williamsons synthesis (b) Stephen reaction. (c) Hell-

Volhard-Zelinsky reaction (d) Aldol Condensation (e) Wolff-Kishner reduction.

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Q. 14. (a) An organic compound (A) (molecular formula C8H16O2) was

hydrolysed with dilute sulphuric acid to give a carboxylic acid (B) and an alcohol

(C). Oxidation of (C) with chromic acid produced (B). (C) on dehydration gives

but-1-ene. Write equations for the reactions involved.

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(b) Predict the products formed when cyclohexanecarbaldehyde reacts with

following reagents.

i. PhMgBr and then H3O+ii. Tollens reagent

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Q. 15. Primary alkyl halide C4H9Br (a) reacted with alcoholic KOH to give

compound (b). Compound (b) is reacted with HBr to give (c) which is an isomer

of (a). When (a) is reacted with sodium metal it gives compound (d), C8H18

which is different from the compound formed when n-butyl bromide is reacted

with sodium. Give the structural formula of (a) and write the equations for all the

reactions.

(ii) Out of C6H5CH2Cl and C6H5CHClC6H5, which is more easily hydrolysed by

aqueous KOH.

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Q. 16. (a) Write the reactions ofglucose with (i) HI (ii)HNO3 (iii)(CH3CO)2O

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(b) Discuss the amphoteric nature of amino acid with suitable example.

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Q. 17. (a) Discuss the following

i. Denaturationii. invert sugar

iii. Globular proteinsAns:

(b) What is glycogen? How is it different from starch?

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(c) Draw the cyclic structures of anomers of glucose.

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Q. 18. (a) CompoundAof molecular formula C3H7Br, yields a compound B

of molecular formula C3H8O when treated with aq. NaOH. On oxidation the

compound B yields a ketone C. Compound C on treating with methyl magnesium

bromide and then H2O in acidic medium gives tertiary butyl alcohol. Deduce the

structures of A, B and C and write the reactions involved. (3 marks)

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(b) Draw the structures of major mono halo products in each of the following

reactions. (2 marks)

(i) (ii)

(2 marks)

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Or

i. Carboxylic acid is a stronger acid than phenol. Why? 2ii. How will you convert ethanal into the following

compounds? 2

(i)Butane-1,3-diol

(ii) But-2-enal

iii. Predict the products formed whencyclohexanecarbaldehyde reacts with Semicarbazide and

weak acid (1 mark

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Inorganic Chemistry

Q. 19. (a) Discuss the chemistry involved in Brown ring test for nitrate ion.

Give equations also. 2 marks

(b) Complete the following equations: 3

i. P4 + SOCl2 ---------------ii. 4 AgNO3 + 2H2O + H3PO4 ------------

iii. NaCl + MnO2 + H2SO4 ------------------Ans:


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Or

(a) Account For the Following: 3

i. H3PO2 act as monobasic acid.ii. Interhalogen compounds are more reactive than

halogens

iii. Bond dissociation energy of F2 is smaller than Cl2.(b) Discuss the quantitative method for estimating O3 gas. (2 marks)

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Q. 20. (i) What are interstitial compounds? Why are such compounds well

known for transition metals? (1 marks)

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(ii) How is the variability in oxidation states of transition metals different

from that of the non transition metals? Illustrate with examples. (1 marks)

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(iii)Describe the preparation of potassium dichromate from iron chromite

ore. What is the effect of increasing pH on a solution ofpotassium dichromate? (2

+ 1 marks)

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Or

(i) Account for the following. (1 x 3 marks)

a. Sc, the first member of first transition series doesntexhibit variable oxidation state. Account for the

following

b. Transition metals have a strong tendency to formcomplexes.

c. Zirconium (atomic no 40) and hafnium (atomic no 72)exhibit similar properties.

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(ii) How does acidified solution of potassium dichromate react with (a) FeSO4

and (b) H2S?

Inorganic Chemistry (p Block Elements)

Q. 1. There is a considerable increase in covalent radius from N to P but from

As to Bi only a small change is observed.

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Q. 2. Ionisation enthalpy of group 15 elements is much higher than that of

group 14 elements.

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Q. 3. Ionic radius of Sb and Bi are very less when compared to the ionic

radius of N,P and As.

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Q. 4. Metallic character of group 15 elements decreases on going down the

group.

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Q. 5. Tendency to show +3 oxidation states in group 15 decreases on going

down the group.

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Q. 6. Nitrogen cant form penta halides.

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Q. 7. Nitrogen exhibits------ bonding while heavier members exhibit--------bonding.

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Q. 8. N2 is a gas while P4 is a solid.

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Q. 9. Catenation tendency is weaker in nitrogen.

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Q. 10. N2 molecule is chemically inert while white phosphorus is more

reactive.

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Q. 11. In group 15, +3 oxidation states is more stable than +5 oxidation state

on going down the group.

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Q. 12. R3 P=O is known but R3 N=O is unknown.

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Q. 13. Basicity of hydrides NH3> PH3 > AsH3 > SbH3 > BiH3

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Q. 14. Stability of hydrides NH3> PH3 > AsH3 > SbH3 > BiH3

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Q. 15. Reducing character of hydrides NH3AsH3


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Q. 21. Both PCl3 and PCl5 fumes in air.

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Q. 22. PH3 has lower boiling point than NH3.

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Q. 23. NH3 acts as a lewis base.

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Q. 24. NO2 molecule dimerises to become N2O4.

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Q. 25. Aluminium is rendered passive in concentrated HNO3.

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Q. 26. Concentrated HNO3 becomes yellow when exposed to light.(Or)

concentrated HNO3 is an oxidizing agent.

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Q. 27. White phosphorus is more reactive than red phosphorus. Black

phosphorus is least reactive.

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Q. 28.Bond angle in PH4+ is higher than that of PH3.

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Q. 29. HNH bond angle in NH3 is less than the tetra hedral bond angle of109.50.

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Q. 30. Bond angles of HPH,HAsH and HSbH are closer to 900.

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Q. 31. H3PO4 is tri protic, H3PO3is diprotic while H3PO2 is mono protic.

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Q. 32. H3PO2 is a good reducing agent.

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Q. 33. H3PO2 is a stronger reducing agent than H3PO3.


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Q. 34. NO is an odd electron molecule but does not dimerise to give N2O2.

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Q. 35. Sulphur has very high boiling and melting point when compared to

oxygen.

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Q. 36. In group 16 tendencies to show -2 oxidation state decreases on going

down the group.

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Q. 37. In group 16 +4 oxidation state become more stable than +6 oxidation

state on going down the group.

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Q. 38. Oxygen can show a maximum covalency of 4 and it can not form hexavalent Ans:compound.

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Q. 39. Acidity of group 16 hydrides arrange in increasing order

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Q. 40. Reducing character of group 16 hydrides arrange in increasing order

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Q. 41. Boiling point of H2O is higher than that of H2 S.

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Q. 42. Sulphur exhibit +6 oxidation state when it combines with fluorine.

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Q. 43. SF6 is exceptionally stable or it cannot be hydrolysed easily.

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Q. 44. SF6 is known while SCl6 is unknown.

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Q. 45. SF6 is known while SH6 is unknown.

Q. 46. H2O is a liquid while H2S is a gas.

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Q. 47. MnO is basic while Mn2O7 is acidic.

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Q. 48. O3 is thermo dynamically unstable than O2 (or) . O3 in higher

concentration is explosive.

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Q. 49. NO gas depletes ozone layer.

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Q. 50. Sulphur in vapour state is paramagnetic.

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Q. 51. HCl and HNO3 are prepared by reacting NaCl and NaNO3 respectively

with H2SO4 while HBr and HI cannot be prepared by this method.


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Q. 52. Cane sugar chars in concentrated sulphuric acid.

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Q. 53. Concentrated sulphuric acid is a good oxidizing agent.

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Q. 54. Two S-O bonds in SO2 are equivalent.

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Q. 55. Ka2 of H2SO4 is


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Q. 57. Fluorine has lesser negative value of electron gain enthalpy than

chlorine.

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Q. 58.All halogens are colored.

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Q. 59. F2 has smaller enthalpy of dissociation than Cl2.

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Q. 60. Fluorine has lesser negative value of electron gain enthalpy than

chlorine but fluorine is a stronger oxidizing agent than chlorine.

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Q. 61. Fluorine shows only -1 oxidation state. Other halogens can exhibit

positive oxidation state.

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Q. 62. Halogens show positive oxidation state when they combine with

oxygen and fluorine atoms.

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Q. 63. Halogens are good oxidizing agent and oxidizing power (reactivity)

decreases with the increase in atomic number.

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Q. 64. Most of reactions of fluorine are exothermic.

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Q. 65. HF is a liquid while other hydrogen halides are gases.

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Q. 66. HF has highest boiling point while HCl has lowest boiling point among

hydrogen halides.

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Q. 67.Acidic strength of hydrogen halides HF HI


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Q. 69. Thermal stability of group 16 hydrides H2O > H2S > H2Se > H2Te

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Q. 70. OF2 is fluoride of oxygen and not oxide of fluorine.

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Q. 71. Oxygen and chlorine has similar electro negativity. Oxygen form

hydrogen bonding but not chlorine.

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Q. 72. Ionic character of halides MF>MCl>MBr>MI

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Q. 73. Electron gain enthalpy of O O- is 141 KJ/mole and O O --> O2- is +

702 KJ/mole.

Large number of oxides having O2- is known and not O-.

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Q. 74. In metal halides, halides in higher oxidation state of the metal is more

covalent than the one in lower oxidation state.(PbCl4 is more covalent than PbCl2)

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Q. 75. Inter halogen compound is more reactive than the halogens from

which it is formed.

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Q. 76. Chlorine is a powerful bleaching agent.

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Q. 77. HCl reacts with Fe to give FeCl2 and not FeCl3

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Q. 78. Fluorine forms only one oxo acid HOF

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Q. 79. Acidity of oxo acids HClO4> HClO3> HClO2> HClO.

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Q. 80. Acidity of oxo acids HOCl>HOBr>HOI

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Q. 81. Oxidizing power of HClO4> HClO3> HClO2> HClO

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Q. 82. Fluorine form fluoride of oxygen while other halogens form oxides of

halogen.

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Q. 83. Group 18 elements are chemically uncreative.

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Q. 84. Group 18 elements have very high ionization enthalpy and it decreases

on going down the group.

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Q. 85. Group 18 elements have positive value of electron gain enthalpy.

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Q. 86. Group 18 elements have lower value of boiling and melting point and

it increases on going down the group.

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Q. 87. Group 18 elements have larger atomic radius.

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Q. 88. Bartlett synthesized XePtF6 from his knowledge of earlier known

compound O2PtF6.

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Q. 89. Xenon forms noble gas compounds.

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Q. 90. Xenon forms compounds only with oxygen and fluorine.

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Q. 91. Helium is used in diving apparatus.

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Q. 92. Oxygen has lesser negative value of electron gain enthalpy than

Sulphur.

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Q. 93. What type of defect reduces the density of unit cell?

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Q. 94. What is the effect of temperature on osmatic pressure of the solution?

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Q. 95. Determine the order of the reaction if its half life is inversely

proportional to theinitial concentration of the reactant.

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Q. 96. Mention two uses of formaldehyde.

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Q. 97. Write the IUPAC name of the compound CH3 OCOCH2 CH2 COO CH3

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Q. 98. The outer electronic configuration of two elements of lanthanoids are

given below

i. 4f1 5d1 6s2ii. 4f7 5d0 6s2. Determine the atomic number of these

elements.

Determine the stable oxidation state of these elements.

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Q. 99. Mention the differences between thermo setting and thermo plasticpolymers.

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Q. 100. Distinguish chemically between

i. Phenol and methanolii. Propan-1-ol and propan-2-ol.

Q. 101. Complete the following chemical equations:

Q. 102. An element A crystallizes in FCC structure. 200g of this element has24x1023 atoms. Density of unit cell is 7.2g/cm3. Calculate the radius of A.

Avagadro number= 6x 1023 mole- 1

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Q. 103. The activation energy of a first order reaction at 270C is 54 KJ/mole.

Activation energy of the same reaction at the same temperature in the presence of

a catalyst is 44 KJ/mole. How many times the reaction rate changes in the

presence ofcatalyst at this temperature? (R=8.314J/K/mole)

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Q. 104. 0.85% solution of NaNO3 is 90% dissociated at 300K.Determine the

osmatic pressure of the solution.( R= 0.0821 L atm/K/mole. Molar mass of

NaNO3=85u) OR Determine the boiling point of 1M solution of KCl. Assume that

KCl is 90% dissociated. Density of KCl solution is 1.05g/cm3. Molar mass of

KCl=74.5u. Kb= 0.52 K Kg mole- 1

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Q. 105

a. How is potassium dichromate prepared from chromiteore?


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b. Write the ionic equation of the reaction involved whenKMnO4 is treated withferrous sulphate solution in acid

medium.

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Q. 106. Using Valence bond theory compare the structure and magnetic

behavior of

i. Ni (CO)4ii. [Ni (CN)4]2- Atomic number of Ni=28

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Q. 107.

i. A radio active element of group 18 undergoes a decay.Determine the position ofthe new nuclide.


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ii. Calculate the mass of 140 La in a sample whose activityis 3.7x1010Bq. Given half life of 140 La = 40 hours.

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Q. 108. Carry out the following conversions:

i. Benzoyl chloride to benzaldehyde.ii. Hex-1-ene to pentanal

iii. Hexane nitrile to 1-amino pentane.Ans:

Q. 109.Account for the following:

i. In ammonalysis of halo alkanes primary amine is theonly product when NH3is taken in large excess.

ii. Tert amine has lower boiling point than primary amineof comparable molarmass,

iii. Amide formed in acylation reaction ofamine, does notreact further withacid halide.


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Q. 110. Describe the following with suitable examples:

i. Double base propellantii. Mordant dyes

iii. Broad spectrum antibiotics.Ans:

microsoft word - chemistry conceptual and important questions for cbse

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