Class 12 Chemistry : Important Questions and Topics for NEB exam.

 Here are important Topics and Questions which are frequently asked in the NEB class 12 exam.

Organic Chemistry:

Preparation of :

• Chloroform (trichloromethane )
• Nitrobenzene
• Formic acid (methanoic acid)
• Aniline
• Diethyl ether (Ethoxy ethane)     

One question sure out of two:

• Identification of 10, 20, and 30 alcohols by Victor Meyer’s method.
• Separation of 10, 20, and 30 amines by Hoffmann’s method.

Name reactions:

1. Aldol condensation reaction
2. Cannizaro’s reaction
3. Perkins condensation
4. Claisen Condensation reaction.
5. Benzoin condensation
6. Carbylamine reaction
7. Reimer Tiemann reaction
8. Coupling reaction( preparation of azo dyes)
9. Diazotization reaction
10. Friedel- Craft’s reaction
11. Hoffmann’s Bromamide reaction( Decarbonylation reaction)
12. Esterification reaction
13. Carbonylation reaction (Oxo process)
14. Williamson's etherification reaction
15. Rosenmund reduction

Test reaction:

1. Iodoform test
2. Silver mirror test( reaction with Tollen’s reagent)
3. Nitrous acid test of 10, 20 and 30 amines.
4. 2,4 – DNP test
5. Carbylamine test ( test of primary amines)

Important reactions:

1. Reduction of nitrobenzene in a different medium.
2. Preparation of alcohols using a Grignard reagent.
3. Oxidation of alcohols.
4. Fermentation
5. All reactions of chloroform

Reactions to prepare : (with one use)

1. DDT                   4. Picric acid
2. BHC                   5. Urotropin
3. Chloropicrin.       6. TNT

Convert:

1. 1-bromopropane to 2- bromopropane and vice versa.
2. 1- propanol to 2- propanol and vice versa.
3. Methanamine to ethanamine and vice versa.
4. Phenol to anisole(methoxy benzene) and vice versa.
5. Ethoxy ethane to methoxy ethane.
6. Phenol/aniline to azo-dye.
7. Ethanal/ ethanol to 3-hydroxy butanal.
8. Ethanol to 2- hydroxy propanoic acid.
9. Propanone(acetone) to 2-hydroxy-2-methyl propanoic acid.
10. Phenol to toluene.
11. Ethanol to propanol/ propanoic acid.
12. Methanamide to ethanamine.

Some Important short questions of Organic Chemistry:

1. Why is chloroform stored in a dark bottle containing ethanol?
2. Why does chloroform not give white ppt. with aq. AgNO3?
3. Why is nucleophilic substitution reaction difficult in haloarene?
4. Why is the boiling point of ethanol greater than that of ethoxy ethane?
5. Why is phenol more acidic than aliphatic alcohol?
6. Why does nitrobenzene undergoes an electrophilic substitution reaction at meta position? ( Explain why –NO2 group is meta directing towards electrophilic aromatic substitution)
7. Why is chlorobenzene o/p – directing towards electrophilic substitution reaction?
8. It is dangerous to boil a sample of ether stored for a long time, give a reason.
9. Ether is stored in a bottle containing iron wire, why?
10. Give a suitable test to distinguish ethanamine from N-methyl methanamine.
11. Write a chemical test to distinguish ethanoic acid(acetic acid) from methanoic acid(formic acid).
12. Why is a chloroacetic acid stronger acid than acetic acid?
13. Why is a formic acid stronger acid than acetic acid?
14. Why an amino group of aniline is protected before nitration? (Aniline can not be nitrated directly, why?)
15. Write the functional isomers of C3H6O with their IUPAC name. Give a chemical test to distinguish them.
16. Write an unsymmetrical ether of C3H8O. How would you prepare this ether using Williamson’s synthesis?
17. Write down possible isomeric amines of C3H9N and give their IUPAC names.
18. What is a peptide bond(linkage)? Write an example of the dipeptide.
19. What are disaccharides? What happens when a disaccharide is hydrolyzed.
20. Define protein. What is meant by denaturation of protein?
21. What is soap? How is soap obtained from fat?(What is saponification?)(What happens when a fat/oil is hydrolyzed?)
22. Write monomers and one use of:

(a)Bakelite    (b)Nylon-6,6

(c)polyvinyl chloride(PVC)     (d) Teflon

23. Write an example and one use of:

• Analgesic, antipyretic, antibiotics, and antiseptic drugs.
• Herbicide and Pesticide
• Germicide and Insecticide
• A synthetic fertilizer – nitrogen fertilizer/Phosphorus (phosphatic) fertilizer, mixed(NPK) fertilizer.

What happens when:

1. Sodium benzoate is heated with soda-lime.
2. Phenol is heated with zinc dust.
3. Chlorobenzene is treated with chloral.
4. Ethyl alcohol(ethanol) is treated with acetic acid(ethanoic acid)
5. Phenol is treaded with aq. Br2.
6. Aniline is treated with aq. Br2.
7. Phenol is treated with benzene diazonium chloride.
8. Ethoxy ethane is treated with excess HI.
9. Methanal(formaldehyde) is treated with ammonia.
10. Methanal/benzaldehyde is treated with NaOH.
11. Ethanal/propanone is treated with NaOH.
12. Aldehyde/ketone is treated with hydroxylamine.
13. Ethanol is heated with conc. H2SO4.
14. Acetic acid is treated with P2O5.

INORGANIC CHEMISTRY :

Extraction of:

1. (Blister) copper from copper pyrites.
2. Steel (Mainly Open Hearth process)
3. Iron from iron pyrites.
4. Zinc from zinc blend ( sulphide ore).
5. Mercury from cinnabar (HgS) ore.

Chemistry of:

1. Blue vitriol ( CuSO4.5H2O)
2. White vitriol ( ZnSO4. 7H2O)
3. Zinc white ( ZnO)
4. Calomel (Hg2Cl2)
5. Corrosive sublimate (HgCl2)

Some Important short questions of Inorganic Chemistry :

1. Copper metal becomes black/green when exposed to air for a long time, why?
2. What happens when copper is treated with conc. HNO3?
3. What is the effect of heat on blue vitriol?
4. What is Rinman’s green? How it is prepared? Write its one important use.
5. Write the molecular formula of Philosopher’s wool. How it is prepared?
6. What is Nessler’s reagent? How is it prepared? Give its one use.
7. What is the composition of stainless steel? Write its one use.
8. Distinguish between quenching and tempering of steel.
9. Rusting (corrosion) of iron and methods of prevention.  — (5 marks too.)
10. Why does silver nitrate produce a permanent black stain on the skin?

PHYSICAL CHEMISTRY :

Short important topics:

1. Selection of indicators.
2. Different concepts of acids and bases and their limitations
3. Common ion effect and solubility product principle and its application.
4. Faraday’s laws of electrolysis.
5. Hess law.
6. Prediction of feasibility/ spontaneity of reactions in terms of free energy change and entropy change.
7. Differences between order and molecularity of a reaction.
8. Collision theory of reaction rate.
9. Factors affecting rate of reaction.

Some Important short questions from physical chemistry :

1. Write hybridization of central atom and geometry of:

• Ethene(ethylene) ,ethane and Ethyne (acetylene)
• NH3  and   BF3           
• H2O and H2S

2. Write any two features and an example of sp3/sp2/sp hybridization.

3. Define the terms:

• Normality and Normality factor
• Endpoint and Equivalent point
• Titration error
• Seminormal solution and Decinormal solution
• Indicator
• Standard solution(primary and secondary) with example.

4. What are primary standard substances? What are the requisites for a substance to be the primary standard?

5. Define molarity and normality. Write their relationship.

6. What happens when HCl is passed through a saturated solution of NaOH?

7. Predict whether the aqueous solution of CuSO4/CaCl2/Na2CO3/NaCl is acidic basic or neutral. Give reason.

8..State Ostwald’s dilution law. What is the limitation of this law?

9. Define pH and pOH. Write their relation.

10. Define the terms:

• Electrochemical equivalent (ECE).
• Standard electrode potential.
• One Faraday

11. Mention one important application of standard hydrogen electrode giving example.

12. State the first law of thermodynamics and point out its limitation.

13. Distinguish between an intensive and extensive property with one example of each.

14. Define enthalpy of combustion and enthalpy of formation.

15. Draw an energy profile diagram for exothermic and endothermic reactions.

16. Draw an energy profile diagram for catalyzed and uncatalyzed reactions.( How does catalyst increases the rate of reaction?)

17. State second law of thermodynamics. Explain this law on the basis of entropy change.

18. What is meant by an effective collision of reacting species? What are the essential conditions for the effective collision of reacting species?

19. Find the unit of rate constant of zero, first, second and third-order reaction.

Note: Numerical problems are most important for physical chemistry, which are not listed here.

Reference: https://chemicalnote.com/