Chemistry | General Stream | Question Paper 2081-2024 of Class 12 | NEB

Group 'A' [11x1=1]

Question No. 1 to 11 (Multiple Choice Questions) will be provided after 30 minutes of starting examination. Rewrite its (MCQ) correct options (answer) in the same answer sheet.

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Group - 'B' 8x5=40

12. An electrochemical cell (galvanic cell) is designed by coupling Zn-electrode with standard hydrogen electrode (SHE).

Given, EZn++/ Zn= - 0.76 V.

1. Draw the galvanic cell. [2]
2. Write down complete cell reaction. [2]
3. Calculate the emf of the cell. [1]

Or

What is Hess's law of constant heat summation ? Calculate the heat of formation of ethanol from the following data :  [1+4]

H ( g ) + 1 O ( g ) → H O(l), H = –286.2 KJ / mol
C (s) + O2 ( g ) → CO2 ( g ), H = –393.2 KJ / mol
C2 H5OH(l) + 3O2 (g) → 2CO2 (g) + 3H2O(l),  H = –1368 KJ / mol

13. Define the following terms.

Lewis base     ii) Basic buffer  [2]
Calculate the pH of solution obtained by mixing equal volumes of two solutions having pH =3 and pH= 5. [3]

14. A heavy metal is extracted from its oxide ore. During extraction, smelting of the calcined ore is done in a blast furnace.

a) Name the metal and the ore. [1]
b) Draw the clean and labelled diagram of the blast furnace showing different zones. [3]
c) Write down the balanced chemical equations of slag formation reactions. [1]

15. Write two methods of preparation of corrosive sublimate. Give its action with

a) excess of KI
b) NH3   [2+2+1]

16. i) Starting from nitrobenzene, how would you prepare aniline ? Convert aniline into :

a) phenyl isocyanide
b) azo-dye  [1+2]

ii) Nitrobenzene prefers electrophilic substitution reaction at meta-position. Explain.  [2]

17. A sequence of chemical reactions is represented as:

a) Identify the compounds (A) and (B).  [1]
b) Write the laboratory test of compound (B).  [1]
c) Starting from compound (B), how would you obtain nitrolic acid ? [2]
d) Predict the product when compound (A) is heated with chloroform in alcoholic medium. [1]

Or,

Make a correct sequence of reactions using suitable conditions and reagents of the following compounds.

Benzene, Benzaldehyde, Toluene, Cinnamic acid, Sodium benzoate, Benzoic acid.

18. Write a chemical equation for each of the following.

a) 2, 4- DNP test [1]
b) Oxo-process [1]
c) Claisen condensation reaction [1]
d) Wurtz-Fittig reaction [1]
e) Carboxylation reaction [1]

19. The chlorinated compound 'A' reacts with acetone to give sleep-inducing drug.

a) How would you prepare compound 'A' by using one of the isomers of C2H6O ? [2]
b) What happens when compound 'A' is:
i) Exposed in air ? [1]
ii) Heated with phenol in the presence of aq. NaOH ? [2]

Group - 'C' 3x8=24

20. a) Distinguish between pseudo first order and first order reaction giving an example of each. [2]
b) Draw an energy profile diagram showing energy of activation for endothermic reaction. [2]
c) The hypothetical data for the reaction, 2A+B→ C, are,

Calculate the rate of formation of 'C' when the concentration of 'A' and 'B' are [0.6] molL-1 and (0.3) molL-1, respectively.  [1+1+1+1]

Or

a) Deduce normality equation.  [2]

b) Give reason.

i) Methyl orange is used as indicator for the titration between H2SO4 and Na2CO3. [1]
ii) Oxalic acid solution is warmed by adding dil.H₂SO₄ before titration with KMnO₄. [1]

c) 0.70 g of a sample of Na2CO3.xH2O was dissolved in water and volume was made 100 ml. 20 ml of this solution required 19.8 ml of N/10 HCl for complete neutralization. Find the value of x. [4]

21. a) Give any two chemical reactions for the preparation of ethanoic acid. [2]
b) How does ethanoic acid react with [2]
i) P2O5         ii) NH3 ?
c) A carbonyl compound 'A' gives both Tollen's and iodoform tests positively.
i) Identify the compound 'A'. [1]
ii) How does the compound 'A' react with dil. NaOH ? Give chemical equation involved. [1]
iii) Write the chemical equation when compound 'A' reacts with HCN followed by hydrolysis. [2]

Or,

a) An aromatic compound (A) undergoes Sandmeyer's reaction to give (B). The compound (B) is reduced with Ni-Al in presence of alkali to give compound (C). The compound (C) further reacts with CH3Cl in the presence of Anhydrous AlCl3.The compound (B) when heated with chloral in acidic medium gives a common insecticide. Identify (A), (B), (C) and (D) giving complete reaction. [4]

b) How do you separate the isomers of C H N by Hoffmann's method? Explain with suitable chemical equations. [4]

22. a) Define homopolymer and co-polymer. [2]
b) Differentiate between paper and pulp. [2]
c) Distinguish between OPC and PPC cement. [2]
d) Write down any two uses of radioisotopes in medical field. [2]

Chemistry General Stream Question Paper 2081-2024 of Class 12 NEB.

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