NEB Class 12 Chemistry Model Question 2079-2023

Regular Students | Subject Code: 3021'H'
Time: 3hrs | Full Marks: 75 | Pass Marks: 27
Candidates are required to give their answers in their own words as far as practicable. The figures in the margin indicate full marks.

Attempt all the questions

Group A


Rewrite the correct options for each question in your answer sheet.

1. 2R-OH+2Na → 2RONa+H2, is an example of

A) acidic nature of alcohol

B) basic nature of alcohol

C) electrophilic substitution reaction

D) nucleophilic substitution reaction

2.C6H5CH2-CHO and C6H5CHO can be distinguished by:

A) Iodoform test

B) Tollen's test

C) 2, 4 - DNP test

D) Fehling test

3. An organic compound (X) undergoes education. with LiAlHto yield (Y). When vapor of u is passed over freshly reduced copper at 300°C (X) is formed. The compound Y is




D) CH3-O-CH3

4. The number of possible structural isomers of 1° amine of molecular formula C4H11N give

A) 1

B) 2

C) 3

D) 4

5. Acetic anhydride is obtained from acetyl chloride by the reaction of

A) Conc.H2SO4

B) P2O5



6. A metal (M) forms thiosulphate with the molecular formula M2S2O3. The valency of metal is

A) 1

B) 2

C) 3

D) 4

7. The PH of 10-8 M aqueous solution of HCL is

A) less than 7

B) 7

C) 8

D) more than 8

8. A catalyst accelerates the reaction because

A) it brings reactants closer

B) it lowers the activation energy

C) it increases the activation energy

D) it forms complex with the reaction

9. What is the concentration of nitrate ions if an equal volume of 1M NaNOand 1m KCL are mixed

A) 0.25M

B) 0.5M

C) 1M

D) 2M

10. Tailing of mercury is due to the formation of

A) HgO

B) Hg2O

C) HgO2

D) Hg2O2

11. Bell metal is an alloy of

A) Cu. Pb and Sn

B) Sn and Cu

C) Zn and Pb

D) Zn, Cu, and Sn

Group B


12. An electrochemical cell is constructed by using aluminum and silver electrodes whose electrodes' potential values are;

E° Al3+/Al = -1.67V

E° Ag+/Ag = 0.80V

i) What is meant by electrochemical cell?

ii) Represent an electrochemical cell using the above electrodes

iii) Write down complete cell reactions

iv) Calculate the emf of the cell.       (1+1+2+1)


Hess's law is applied to calculate the different types of enthalpy of reactions 

i) Define Hess's Law of constant heat summation.

ii) What is meant by the enthalpy of reaction?

iii) Standard enthalpy of formation of  H2O2(l) and H2O (l) is 188kj/mol and 286 KJ/mol respectively. What will be the enthalpy change of the following reaction:

2H2O2(l) --> 2H2O(l)+O2(g). (1+1+3)

13. Ionic product of water at 25° C is 1x10ˆ-14 and water is a very weak electrolyte.

i) Define the ionic product of water.

ii) Deduce the reaction Kw = [H+] [OH]

iii) Calculate the [OH-] concentration of 0.01M HCL at 25°C

iv) What is the effect of temperature on the ionic product of water?  (1+1+2+1)

14. Ethyl alcohol is common alcohol and is used to manufacture alcoholic beverages. It can be prepared from sugar-containing materials like molasses by a fermentation process.   (1+1+1+1+1)

i) Define fermentation

ii) What is meant by molasses?

iii) MEntion the function of yeast in the fermentation of ethyl alcohol.

iv) Write a chemical reaction for the conversion of cane sugar into ethyl alcohol.

v) Give a difference between absolute alcohol and denatured alcohol.

15. A carbonyl compound (M) contains three carbon atoms and it undergoes the iodoform test. 

i) identify the compound (M)

ii) write down a chemical reaction for the preparation of (M)

iii) How is (M) converted into propane?

iv) Predict the final product obtained when (M) is treated with CH 3Mgl in presence of dry ether and followed by hydrolysis?

v) Give a laboratory test reaction of the carbonyl compound.


Convert ethoxy ethane from a halo alkane C25Br by using Williamson's reaction.

i) What product is obtained when ethoxyethane is heated with excess Hl?

ii) Why are old samples of ether not distilled to dryness in the air?

iii) Convert phenol into anisole.   (1+2+2)

16. For the following reaction sequence.

i) Write down reagents and conditions for reaction (1), reaction (2), reaction (3), and reaction (4).

ii) Identify the compound (z) giving IUPAC name.  (4+1)

17. How would you apply Hoffmann's method for the separation of 1°, 2°, and 3° amine from their mixture?   (5)

18. An important compound nontypical transition metal zinc which is used as an eye lotion and is also called white vitriol.  (5x1)

i) Write down a method of preparation of white vitriol.

ii) What happens when white vitriol is heated to 800°C?

iii) Define double salt giving an example of it

iv) How is Lithopone obtained from white vitriol.

v) Why is zinc considered a non-typical transition metal.

19. Steel manufactured by open Hearth process.   (1+2+1+1)

i) What is the open Heart process?

ii) Write down the chemical reactions occurring in Open-Hearth Furnace.

iii) Why is Speigeleisen added in the Open-Hearth Furnace?

iv) Write down the composition of stainless steel.   

Group C



20. a) Write an example of each of the following reactions. 

i) Hydroboration oxidation

ii) Decarbonylation

iii) Sandmeyer's reaction 

iv) iodoform reaction

v) Elimination reaction

vi) Cannizzaro's reaction

vii) Reimer-Tiemann reaction

viii) Fridel Craft alkylation


An unsaturated hydrocarbon (C3H6) undergoes Markovikov's rule to give (A). Compound (A) is hydrolyzed with aqueous alkali to yield (B). When (B) is treated with PBr3, compound (C) is produced. (C) reacts with AgCN (alc.) to give another compound (D). The compound (D) if reduced with LiAlH4, produces (E).

i) Define Markovikov's rule.

ii) Identify (A), (B), (C), (D) and (E) with chemical reaction.

iii) How does E react with nitrous acid?

iv) How would you convert (B) into C3H8?  (1+5+1+1)

21. a) For a hypothetical chemical reaction mP + n Q--> z; the rate Law is, rate = K [P]ˆm [Q]ˆn. Where K is the rate constant of the reaction (m+n) is the overall order.   (4+1) 

i) Define rate Law.

ii) Why is rate law an experimental parameter? 

iii) What is meant by the rate constant?

iv) Mention a difference between the order and molecularity of a reaction.

b) For the above reaction, the order reaction with respect to P and Q are first order and Zero order respectively. Experimental data obtained from the reaction are; as below.


i) Identify the value of A, B, and C

ii0 Calculate rate constant [K].   (3+1)


a) Crystal of oxalic acid is generally used to prepare a primary standard solution.  (1+1+1+1)

i) Define the Primary Standard solution.

ii) Which chemical indicator is used in the titration of KMnOsolution versus oxalic acid solution?

iv) Mention a major application of titration in a quality control laboratory.

b) An aqueous solution of a dibasic acid containing 17.7 gm of an acid per liter of the solution, has a density of 1.0077 gm/liter (molar mass of the acid = 118gm/mol) Calculate; i) molarity ii) morality (2+2)

22. a) i) What is Portland cement?

ii) Name the major components present in Portland cement.

iii) Why is gypsum used in clinker during the cement production process?

iv) Give any two instruments used for quality control of cement.  (1+1+1+1)

b) i) Differentiate between homo-polymer and co-polymer given an example of each.

ii) Name the monomers of the following polymer and also write their molecular formula.

a) Polystyrene

b) Bakelite. (2+2)