Download Bihar Board (BSEB) Class 12th Chemistry Question Paper Exam 7.2.2026. Answer of all the 70 objective questions are given below in quiz or mock test format. Students can check their answer. Practice these questions for next year annual exam.
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Bihar Board (BSEB) 12th Chemistry Solved Paper 2026
Bihar Board Class 12
Chemistry Objective Questions Answer Key 2026
Section-A | 70 Objective Type Questions
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Section - B: Short Answer Type Questions
Note: Question number 1 to 20 are Short Answer Type. Answer any 10 questions. Each questions carry 2 marks. 2 x 10 = 20
1. What is called artificial sweetener? Give an example.
Answer: Artificial sweeteners are synthetic chemical compounds that provide a sweet taste similar to sugar but contain significantly fewer or no calories. They are often used by individuals with diabetes or those looking to reduce calorie intake.
Example: Aspartame or Saccharin.
2. What is Buna-N-rubber?
Answer: Buna-N, also known as Nitrile rubber, is a synthetic rubber copolymer produced from 1,3-butadiene and acrylonitrile. It is highly resistant to oil, fuel, and other chemicals.
3.Mention the utility of DNA fingerprinting.
Answer: DNA fingerprinting is utilized for:
- Identifying individuals in forensic investigations.
- Establishing biological relationships, such as paternity testing.
- Identifying genetic disorders and studying genetic diversity.
4. Write structural formulae of the following:
(a) 2-Aminoethanol
(b) N-Ethylethanamine
Answer:
- (a) 2-Aminoethanol: NH2-CH2-CH2-OH
- (b) N-Ethylethanamine: CH3-CH2-NH-CH2-CH3
5. Write IUPAC names of the following:
(a) Lactic acid
(b) Tartaric acid.
Answer:
- (a) Lactic acid: 2-Hydroxypropanoic acid.
- (b) Tartaric acid: 2,3-Dihydroxybutanedioic acid.
6. What is Fehling's solution?
Answer: Fehling's solution is a chemical reagent used to differentiate between water-soluble carbohydrate and ketone functional groups. It consists of two separate solutions: Fehling's A (aqueous copper(II) sulfate) and Fehling's B (alkaline sodium potassium tartrate).
7. What is metamerism? Give example.
Answer: Metamerism is a type of structural isomerism where isomers have the same molecular formula but differ in the distribution of carbon atoms on either side of a functional group (like -O-, -S-, or -NH-).
- Example: Diethyl ether (C2H5-O-C2H5) and Methyl propyl ether (CH3-O-C3H7).
8. What is called rectified spirit?
Answer: Rectified spirit is highly concentrated ethanol that has been purified by means of repeated distillation.It typically contains about 95% alcohol and 5% water by volume.
9. How would you obtain the following compounds from ethyl bromide?
(a) Ethene
(b) Diethyl ether.
Answer:
- (a) Ethene: By heating ethyl bromide with alcoholic Potassium Hydroxide (KOH).
(CH3CH2Br + KOH(alc.) → CH2=CH2 + KBr + H2O). - (b) Diethyl ether: By reacting ethyl bromide with sodium ethoxide (Williamson's synthesis).
(C2H5Br + C2H5ONa → C2H5-O-C2H5 + NaBr).
10. Write IUPAC names of the following complex compounds:
(a) [Co(NH3)5Cl]Cl2
(b) K3[Fe(C2O4)3]
Answer:
- (a) [Co(NH3)5Cl]Cl2: Pentaamminechlorocobalt(III) chloride
- (b) K3[Fe(C2O4)3]: Potassium trioxalatoferrate(III)
11. Why do transition elements form complex compounds?
Answer: Transition elements form complexes because:
- They have small ionic sizes and high ionic charges.
- They possess vacant (n-1)d orbitals that can accept lone pairs of electrons from ligands.
12. What are called interhalogen compounds? Give examples.
Answer: Interhalogen compounds are molecules containing two or more different halogen atoms and no atoms from any other group.
- Examples: IF7, ClF5, and ICl.
13. Dioxygen is a gas whereas sulphur is solid at room temperature. Give reason.
Answer: Dioxygen (O2) exists as a small diatomic molecule held by weak van der Waals forces.Sulphur (S8) exists as a large puckered ring structure (S8) with much stronger van der Waals forces due to its higher molecular mass, making it a solid.
14. Give the structure and basicity of orthophosphoric acid.
Answer:
- Structure: It consists of a central Phosphorus atom double-bonded to one Oxygen and single-bonded to three -OH groups (H3PO4).
- Basicity: It is a tribasic acid because it contains three replaceable hydrogen atoms bonded to oxygen.
15. Differentiate between Roasting and Calcination.
Answer:
- Roasting: The process of heating ore (usually sulphide ores) in the presence of excess air.
- Calcination: The process of heating ore (usually carbonate or hydrated ores) in the absence or limited supply of air to remove volatile impurities.
16. Write a short note on Brownian movement.
Answer: Brownian movement is the continuous, zig-zag, and random motion of colloidal particles in a dispersion medium.It is caused by the unbalanced bombardment of the particles by the molecules of the dispersion medium.
17. What is Pseudo first order reaction? Give example.
Answer: A reaction that is not truly of first order but becomes first order under certain conditions (usually when one reactant is in large excess) is called a pseudo first order reaction.
- Example: Inversion of cane sugar or Acid-catalyzed hydrolysis of ethyl acetate.
18. What is the function of salt bridge in Electrochemical cell?
Answer: The salt bridge serves two main functions:
- It completes the electrical circuit by allowing the flow of ions.
- It maintains electrical neutrality in both half-cells.
19. What are the differences between Ideal solution and Non-ideal solution?
Answer:
- Ideal Solution: Obeys Raoult's law at all concentrations and temperatures;
Δ Hmix = 0 and Δ Vmix = 0. - Non-ideal Solution: Does not obey Raoult's law;
Δ Hmix ≠ 0 and Δ Vmix ≠ 0.
20. How many tetrahedral and octahedral voids are there in a closed packing of N spheres?
Answer: In a closed packing of N spheres:
- Number of Octahedral voids: N
- Number of Tetrahedral voids: 2N
Section - C: Long Answer Type Questions
Note: Question number 21 to 26 are Long Answer Type Questions. Answer any 3 questions. Each questions carry 5 marks. 3 x 5 = 15
21. How many types of crystals are there? Explain them in brief.
Answer: Crystalline solids are classified into four types based on the nature of intermolecular forces:
- Molecular Crystals: Consist of molecules held together by Van der Waals forces or hydrogen bonds (e.g., Ice, Iodine).
- Ionic Crystals: Consist of positive and negative ions held by strong electrostatic forces (e.g., NaCl, KNO3).
- Covalent (Network) Crystals: Atoms are linked by a continuous network of covalent bonds (e.g., Diamond, Quartz).
- Metallic Crystals: Consist of metal kernels in a sea of delocalized electrons held by metallic bonds (e.g., Iron, Copper).
22. What do you understand by Primary and Secondary cells? Mention giving one example of each.
Answer:
- Primary Cells: These are cells in which the redox reaction occurs only once and the cell becomes dead after use over a period of time. They cannot be recharged.
Example: Dry cell (Leclanché cell). - Secondary Cells: These are cells that can be recharged by passing an electric current through them in the opposite direction. They can be used again and again.
Example: Lead storage battery.
23. Explain extraction of copper from copper pyrite.
Answer: The extraction involves several steps:
- Crushing and Concentration: The ore (CuFeS2) is crushed and concentrated by the Froth Floatation process.
- Roasting: Concentrated ore is heated in excess air. Sulphur and Arsenic are removed as volatile oxides.
2CuFeS2 + O2 → Cu2S + 2FeS + SO2 - Smelting: Roasted ore is heated with sand (SiO2) and coke. Iron is removed as slag (FeSiO3).
- Bessemerization: The molten matte is treated in a Bessemer converter to get "Blister Copper."
- Refining: The crude copper is refined electrolytically to obtain 99.9% pure copper.
24. What are halogens? Write their names and electronic configurations. Throw light on the tendency of halogen to form hydrides.
Answer: Halogens are Group 17 elements. They are highly reactive non-metals.
- Names & Configurations:
- Fluorine (F): [He] 2s2 2p5
- Chlorine (Cl): [Ne] 3s2 3p5
- Bromine (Br): [Ar] 3d10 4s2 4p5
- Iodine (I): [Kr] 4d10 5s2 5p5
- Tendency to form Hydrides: All halogens react with hydrogen to form volatile halides of the formula HX. The reactivity towards hydrogen decreases from Fluorine to Iodine. The stability of these hydrides decreases down the group (HF > HCl > HBr > HI) due to the increase in bond length.
25. What type of compound is an alcohol? How is monohydric alcohol classified?
Answer: Alcohols are organic compounds containing one or more hydroxyl (-OH) groups attached to a carbon atom.
Monohydric alcohols (containing one -OH group) are classified based on the hybridization of the carbon atom to which the -OH is attached:
- Primary (1°) Alcohol: -OH group is attached to a primary carbon (e.g., Ethanol, CH3CH2OH).
- Secondary (2°) Alcohol: -OH group is attached to a secondary carbon (e.g., Isopropyl alcohol).
- Tertiary (3°) Alcohol: -OH group is attached to a tertiary carbon (e.g., tert-Butyl alcohol).
26. Write IUPAC names of the following structures.
Answer: Based on the structures provided in the document images:
- (a) CH3-CH(CH3)-CH2-CHO: 3-Methylbutanal
- (b) CH3-CH2-CHO: Propanal
- (c) CH3-C(CH3)2-CO-CH3: 3,3-Dimethylbutan-2-one
- (d) CHO-CHO: Ethanedial (Glyoxal)
- (e) CCl3CHO: 2,2,2-Trichloroethanal (Chloral)