NEB-Grade- XII Chemistry Question-2076 (2019)

Sub. Code: 212 ‘B’

NEB-GRADE XII

2076(2019)

Chemistry

Time: 3hrs                                                                               Full Marks:75

                                     Pass Marks: 27 (only for partial students)

Candidates are required to give their answers in their own words as far as practicable. The figure in the margin indicates full marks.

Group ‘A’

Attempt any fifteen questions.                                                          15x2=30

1.    How would you confirm that B in BF₃ gets SP² hybridization?

2.    Distinguish between decinormal and decimolar solution.

3.    Find the P^H of 1x10^-5 N H₂So_4.

4.    How many coulombs are required to produce?

                     i.        27gm of silver from AgNO₃?

                    ii.        50gm of Aluminum from Al₂O₃?

[At. Wt. of Ag= 108, At. wt. of Al=27]

5.    Define state function. Write any two examples of it.

6.    Calculate entropy change (ΔS) and free energy change (ΔG) for the conversion of ice into water at equilibrium condition when enthalpy change (ΔH) is 9KJ/ mol.

7.    You are given a rate law equation, Rat= K [A]² [B]. By how many times will the rate increase or decrease for the reaction if

8.    Write down correct reactions for the conversion of ethyne into BHC.

9.    Why is haloarene less reactive than benzene in electrophilic substitution reaction?

10.  Starting from phenol how would you obtain

i.             phenolphthalein

ii.            p-hydroxy azobenzene.

12.  An organic compound C₃ H₆ O gives orange precipitate with 2-4 dinitrophenyl hydrazine but does not produce silver mirror with tollen’s reagent. Identify the compound and write the reaction involved.

13.  Why is nitro group called an ambident group?

14.  Write an example of each of the following reactions:

i.             Decarboxylation

ii.            Coupling reaction

15.  Write down the functional isomer of methyl methanoate. What product would you expect when the isomer is heated with P₂ O₅?

16.  How does DNA differ from RNA in respect of sugar and base units present in it?

17.  Define sugar and non-sugar giving an example of each.

18.  Mention an important function of each of the following:

i.             DDT

ii.            Nitrogen fertilizer

iii.           Broad spectrum antibiotics

iv.           Tranquilizers

19.  What is meant by homo-polymerization? Write an example of such polymer.

20.  How is lithophone prepared? Write its one important application.

21.  Why is silver nitrate solution used for staining fingers of voters during election?

22.  What is meant by

i.             quenching of steel

ii.            annealing of steel

Group ‘B’

Attempt any five questions.                                                     5x5=25

23.  Are all standard solutions, primary standard solutions or not? Give reason.

I am of a divalent metal was dissolved in 25ml of 2NH₂SO₄ (f= 1.01). The excess acid required 15.1ml of 1N-NaOH (f=0.8) for complete neutralization. Find the atomic weight of the metal. 

24.  Mention the important application of standard hydrogen electrode. 

i.             Draw the standard cell notation.

ii.            Identify the anode and cathode as the current drawn from it.

iii.           Write the cell reaction taking place at the electrodes.

iv.           Calculate standard cell potential.

25.  Define bond dissociation energy. The bond dissociation energy of H₂(g) and Cl₂ (g) are 435 KJ/ mol and 243 KJ / mol respectively. The enthalpy of formation of HCl(g) = - 92 KJ/mol. Calculate the bond dissociation energy of HCl(g).

26.  How is blister copper extracted from copper pyrites?

27.  Starting form CH₂ Mgl how would you prepare

i.             Propan-2-ol

ii.            2- methyl propan-2-ol.

28.  How is trichloromethane prepared in the laboratory? Why is chloroform stored in a dark room air tied bottle containing a little ethyl alcohol?

 

Group ‘C’

Attempt any two questions.                                                    2x10=20

 The compound  can be obtained by heating toluene in presence of  CeO₂ / H⁺.

   31.  a. How is ethanal prepared from

i.             ethyne

ii.            But-2-ene

iii.           1, 1-dichloroethane?

Write down suitable method for the conversation of ethanal into 2-hydroxy propanoic acid.

b.          Write down a structural formula of primary, secondary and tertiary amine of each from C₃ H₉ N. How is Hoffmann’s method applied to separate them from their mixture?

         32.  Define the terms

i.           activation energy

ii.          order of reaction

iii.         molecularity of reaction

iv.         effective collision

v.          rate law equation. 

Why does powder sugar dissolve faster than grain sugar?

The following data were obtained for a hypothetical reaction

.

Expt.	[x] mol L-1	[y] mol L-1	Formation of z mol L-1 S-1
1.     1	0.20	0.20	3x10-3
2.     2	0.40	0.20	1.2 x10-2
3.     3	0.20	0.40	6x10-3
4.     4	0.60	0.20	9x10-3

  Calculate the rate constant and find out rate of disappearance of y when [x]=0.2 mol L^-1.

33.   Write short notes on any two.                                                 2x5=10

i.             Chemistry of rusting theory of iron

ii.            Extraction of mercury from cinnabar

iii.           Laboratory preparation of anhydrous formic acid

iv.           Lewis concept of acid and base.

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