Chemistry: Solved Previous Year’s Question Paper for NCERT/CBSE  Class 12th Chemistry Paper Code (HSEIIRKN15–6417—X)

Chemistry: Solved Previous Year’s Question Paper for NCERT/CBSE  Class 12th Chemistry Paper Code (HSEIIRKN15–6417—X)

Short Answer Type Questions (Each carry 3 Marks)

Question: What is Arrhenius Equation? What is its importance?

Answer: The Arrhenius equation is a mathematical equation used to calculate the rate at which a reaction occurs.

It is an important tool for understanding the effects of temperature on reaction rates. The equation takes into account the energy required for the reaction to occur and the temperature at which the reaction occurs. The equation states that the rate of a reaction is proportional to a constant multiplied by the exponential energy required for the reaction, divided by the absolute temperature of the reaction. This equation is important for predicting how various factors, such as temperature and pressure, will affect the rate of a reaction.

Question: Give the points of difference between Absorption and Adsorption.

Answer: Absorption:

1. It is a process of taking in one substance by another.

2. It is a diffusion process.

3. It involves the transfer of molecules from a less concentrated region to a more concentrated region.

4. It is a physical process.

5. It is irreversible.


1. It is a process in which molecules of one substance become attached to the surface of another.

2. It is a surface phenomenon.

3. It involves the transfer of molecules from a more concentrated region to a less concentrated region.

4. It is a physical-chemical process. 5. It is reversible.

Very Short Answer Type Questions (Each carry 2 Marks)

Question: What is a Fuel cell? Write the equation which occurs at the electrode in a fuel cell.

Answer: A fuel cell is an electrochemical device that converts chemical energy from fuel into electrical energy. It works similarly to a battery, but unlike a battery, a fuel cell does not run down or require recharging. The equation which occurs at the electrode in a fuel cell is as follows:

 Anode: Oxidation of fuel (Hydrogen) → 2H+ + 2e-

Cathode: Reduction of oxidant (Oxygen) → O2 + 4e-

Overall Reaction: 2H2 + O2 → 2H2O + electrical energy

Question: How is activation Energy affected by the rise in temperature?

Answer: As temperature rises, activation energy is lowered. This means that reactions will occur faster as temperature increases, as less energy is required to initiate the reaction.

Question: Describe the purification of Bauxite ore by Baeyer’s Process

Answer: Baeyer’s Process is a chemical process used to purify bauxite ore. The process involves treating the ore with a solution of caustic soda and hot water, which dissolves the aluminum hydroxide and other impurities. The aluminum hydroxide is then precipitated out of the solution by the addition of carbon dioxide gas, leaving a solution of sodium aluminate. The sodium aluminate is then filtered and purified to produce a white powder, which is pure aluminum oxide. The purified aluminum oxide is then mixed with other chemicals to produce aluminum metal.

Question: Starting from phenol how phenolphthalein is obtained?

Answer: Phenolphthalein can be obtained by reacting phenol with sodium and ethylene glycol in the presence of an acid catalyst. The reaction produces a phenol-ethanol ester, which is then treated with a solution of sodium hydroxide to form phenolphthalein.

Question: Give Hinsberg’s test by which amines can be identified.

Answer: Hinsberg’s test is a chemical test used to differentiate primary, secondary, and tertiary amines. It is based on the reaction of amines with benzene sulfonyl chloride (PhSO2Cl). Primary amines react with PhSO2Cl to form a precipitate of the corresponding sulfonamide, while secondary and tertiary amines remain in the solution.

Question: What are Antimicrobials? Give an example.

Answer: Antimicrobials are substances that can kill or inhibit the growth of microorganisms such as bacteria, fungi, and viruses. Examples of antimicrobials include antibiotics, antifungals, antivirals, and antiseptics.

Objective Type Questions (Each carries 1 Marks)

(i) In b.c.c unit cell the total number of atoms per unit cell is ————-

Answer: 8

(ii) Zinc is mainly extracted from———————-

Answer: Sulfide ores.

(iii) Methyl Isocyanide on reduction with hydrogen in presence of Ni forms —————————

Answer: Methyl Cyanide

(iv) Penicillin is a broad-spectrum antibiotic (True/False)

Answer: True

(v) Lipids are nucleic acids occurring in plants (True/False)

Answer: False

(vi) Acetaldehyde when heated with caustic alkalies it forms Ethyl alcohol and sodium acetate (True/False)

Answer: True

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