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12th Standard Chemistry English Medium Reduced Syllabus Important Questions with Answer key - 2021 Part - 1

12th Standard

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Chemistry

Time : 02:45:00 Hrs
Total Marks : 165
    Multiple Choice Questions
    15 x 1 = 15
  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. The following set of reactions are used in refining Zirconium 
    \((impure)+2I_{ 2 }\overset { 523k }{ \longrightarrow } ZrI_{ 4 }\)
    \({ ZrI }_{ 4 }\overset { 1800K }{ \longrightarrow } Zr(pure)+{ 2I }_{ 2 }\) 
    This method is known as 

    (a)

    Liquation

    (b)

    van Arkel process

    (c)

    Zone refining

    (d)

    Mond’s process

  3. In diborane, the number of electrons that accounts for banana bonds is

    (a)

    six

    (b)

    two

    (c)

    four

    (d)

    three

  4. The compound that is used in nuclear reactors as protective shields and control rods is

    (a)

    Metal borides

    (b)

    metal oxides

    (c)

    Metal carbonates d) metal carbide

    (d)

    none of these

  5. Which of the following d block element has half filled penultimate d sub shell as well as half filled valence sub shell?

    (a)

    Cr

    (b)

    Pd

    (c)

    Pt

    (d)

    none of these

  6. In acid medium, potassium permanganate oxidizes oxalic acid to

    (a)

    oxalate

    (b)

    Carbon dioxi

    (c)

    acetate

    (d)

    acetic acid

  7. 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.

  8. Which one of the following is not correct?

    (a)

    La(OH)2 is less basic than Lu(OH)3

    (b)

    In lanthanoid series ionic radius of Ln3+ ions decreases

    (c)

    La is actually an element of transition metal series rather than lanthanide series

    (d)

    Atomic radii of Zr and Hf are same because of lanthanide contract

  9. Which one of the following pairs represents linkage isomers?

    (a)

    [Cu(NH3)4][ptCl4] and [pt(NH3)4][CuCl4]

    (b)

    [Co(NH3)5(NO3)]SO4 and [Co(NH3)5(ONO)]

    (c)

    [Co(NH3)4(NCS)2]ct and [Co(NH3)4(SCN)2]Cl

    (d)

    both (b) and (c)

  10. Potassium has a bcc structure with nearest neighbor distance 4.52 A0 . its atomic weight is 39. its density will be

    (a)

    915 kg m-3

    (b)

    2142 kg m-3

    (c)

    452 kg m-3

    (d)

    390 kg m-3

  11. Predict the rate law of the following reaction based on the data given below 
    \(2A+B\longrightarrow C+3D\)

    Reaction number [A] (min) [B] (min) Initial rate (M s-1)
    1 0.1 0.1 x
    2 0.2 0.1 2x
    3 0.1 0.2 4x
    4 0.2 0.2 8x
    (a)

    rate=k[A]2[B]

    (b)

    rate=k[A][B]2

    (c)

    rate=k[A][B]

    (d)

    rate=k[A]1/2[B]1/2

  12. The solubility of BaSO4 in water is 2.42 ×10-3gL-1 at 298K. The value of its solubility product(Ksp) will be (Given molar mass of BaSO4 =233g mol 4-1)

    (a)

    1.08 ×10-14mol2L-2

    (b)

    1.08 ×10-12mol2L-2

    (c)

    1.08 ×10-10mol2L-2

    (d)

    1.08 ×10-8mol2L-2

  13. Electrolyte KCl KNO3 HCl NaOAC NaCl
    Λ-
    (Scm2 mol-1)
    149.9 145.0 426.2 91.0 126.5

    Calculate ΛoHoAC using appropriate molar conductances of the electrolytes listed above at infinite dilution in water at 25oC.

    (a)

    517.2

    (b)

    552.7

    (c)

    390.7

    (d)

    217.5

  14. CH3Br \(\overset { KCN }{ \longrightarrow } (A)\overset { { H }_{ 2 }{ O }^{ + } }{ \longrightarrow } (B)\overset { { PCl }_{ 5 } }{ \longrightarrow } \) (C) product (c) is

    (a)

    acetylchloride

    (b)

    chloro acetic acid

    (c)

    \(\alpha\)- chlorocyano ethanoic acid

    (d)

    none of these

  15. Assertion: p – N, N – dimethyl amino benzaldehyde undergoes benzoin condensation
    Reason: The aldehydic (-CHO) group is meta directing.
    Codes:
    (A) if both assertion and reason are true and reason is the correct explanation of assertion.
    (B) if both assertion and reason are true but reason is not the correct explanation of assertion.
    (C) assertion is true but reason is false
    (D) both assertion and reason are false

    (a)

    if both assertion and reason are true and reason is the correct explanation of assertion.

    (b)

    if both assertion and reason are true but reason is not the correct explanation of assertion.

    (c)

    assertion is true but reason is false

    (d)

    both assertion and reason are false

  16. 2 Marks
    15 x 2 = 30
  17. Discuss the use of an acidic flux in metallurgy.

  18. Name some depressing agents

  19. Name the building block of zeolites. Why zeolites have high porosity?

  20. Why transition elements form complexes? 

  21. Explain briefly seven types of unit cell

  22. A compound made up of two atoms X and Y has a face centred cubic arrangement. X is present in the coners and Y at the centre of each face. If one atom is missing from comer. What is the simplest formula of the compound.

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

  24. The rate law for a reaction of A, B and C has been found to be rate =k[A]2[B][L]3/2 How would the rate of reaction change when
    (i) Concentration of [L] is quadrupled
    (ii) Concentration of both [A] and [B] are doubled
    (iii) Concentration of [A] is halved
    (iv) Concentration of [A] is reduced to \(\left( 1/3 \right) \) and concentration of [L] is quadrupled.

  25. 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 \({ t }_{ \frac { 1 }{ 2 } }\)

  26. Indentify the conjugate acid base pair for the following reaction in aqueous solution
    i) HS- (aq) + HF \(\rightleftharpoons \) F-(aq) + H2S(aq)
    ii) HPO2-+ SO32- \(\rightleftharpoons \) PO43-+HSO3-
    iii) NH4+ CO32-  \(\rightleftharpoons \) NH3+HCO3-

  27. Why is anode in galvanic cell considered to be negative and cathode positive electrode?

  28. Thermal decomposition of KClO in presence of MnO2 proceeds as follows.
    Steps in the reaction 2KClO → 2KCl+3Ocan be given as

  29. How is propanoic acid is prepared starting from
    (a) an alcohol
    (b) an alkylhalide
    (c) an alkene

  30. There are two isomers with the formula  CH3NO2. How will you distinguish between them?

  31. Write short notes on the following
    i. Hofmann’s bromide reaction
    ii. Ammonolysis
    iii. Gabriel phthalimide synthesis
    iv. Schotten – Baumann reaction
    v. Carbylamine reaction
    vi. Mustard oil reaction
    vii. Coupling reaction
    viii. Diazotisation
    ix. Gomberg reaction

  32. 3 Marks
    15 x 3 = 45
  33. What is gravity separation? (or) Explain hydraulic washing?

  34. Explain roasting with an example.

  35. Distinguish Roasting and Calcination

  36. What is meant by aluminotherrnitc process?

  37. List the applications of gold

  38. How is boron trifluoride obtained from boron trioxide?

  39. Find out the oxidation state of carbon in each of the following:
    (i) CaC2
    (ii) H2CO3
    (iii) HCN
    (iv) CO

  40. Name a reaction for the estimation of Ozone.

  41. Discuss the anomalous nature of fluorine.

  42. Predict the product
    (i) PCI5+ C2H5OH \(\longrightarrow \)?
    (ii) P4+ SO2Cl2 \(\longrightarrow \) ?
    (iii) POCl3 + H2O \(\longrightarrow \) ?
    (iv) HBr + PH3\(\longrightarrow \) ? :,
    (v) PCl3+ H2O\(\longrightarrow \) ?

  43. Write the properties of interstitial compound.

  44. Mohr's salt answers the presence of Fe2+, NH4+and SO42- ions, whereas the potassium ferrithiocyanate will not answer Fe3+ and SCN ions give reason.

  45. Give the characteristics of first order reaction.

  46. What are drugs? How are they classified

  47. Write the structural formula of aspirin.

  48. 5 Marks
    15 x 5 = 75
  49. Explain the principle of electrolytic refining with an example.

  50. Deduce the oxidation number of oxygen in hypofluorous acid – HOF.

  51. Why first ionization enthalpy of chromium is lower than that of zinc?

  52. if NaCl is doped with 10-2 mol percentage of strontium chloride, what is the concentration of cation vacancy

  53. The half life of the homogeneous gaseous reaction SO2Cl2 → SO2 + Cl2 which obeys first order kinetics is 8.0 minutes. How long will it take for the concentration of SO2Cl2 to be reduced to 1% of the initial value?

  54. Benzene diazonium chloride in aqueous solution decomposes according to the quation \({ C }_{ 6 }{ H }_{ 5 }{ N }_{ 2 }Cl\longrightarrow { C }_{ 6 }{ H }_{ 5 }Cl+{ N }_{ 2 }\) Starting with an initial concentration of 101 g L-1, the volume of N2 gas obtained at 50 °C at different intervals of time was found to be as under:

    t(min) 6 12 18 24 30 \(\infty \)
    Vol.of N2 (ml) 19.3 32.6 41.3 46.5 50.4 58.3

    Show that the above reaction follows the first order kinetics. What is the value of the rate constant?

  55. Write the expression for the solubility product of Ca3 (PO4)2

  56. Write the expression for the solubility product of Hg2Cl2 .

  57. A copper electrode is dipped in 0.1M copper sulphate solution at 25oC . Calculate the electrode potential of copper.[Given: E0Cu2+|Cu = 0.34V].

  58. Explain any one method for coagulation

  59. Explain intermediate compound formation theory of catalysis with an example

  60. Write the differences between nitro methane and nitro benzene

  61. Elucidate the structure of fructose.

  62. Write a note on drug target interaction.

  63. Explain the prepareation of Bakelite and Give its use.

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