SOLUTIONS
2024 BOARD EXAM
CBSE CLASS 12-PCM CHEMISTRY Board Paper 2024 — Set 1
2024
CHEMISTRY
CLASS 12-PCM
CBSE EXAMINATION PAPER-2024
CHEMISTRY
(Solved)
General Instructions :
Read the following instructions carefully and follow them :
- This question paper contains 29 questions. All questions are compulsory.
- This question paper is divided into 3 sections.
- Section A – questions number 1 to 13 are case based questions
- Section B – questions number 14 to 27 are multiple choice questions
- Section C – questions number 28 to 29 are very short answer
- There is no overall choice given in the question paper. However, an internal choice has been provided in few questions.
- Use of calculator is NOT allowed.
Section A
Batteries and fuel cells are very useful forms of galvanic cell. Any battery or cell that we use as a source of electrical energy is basically a galvanic cell. However, for a battery to be of practical use it should be reasonably light, compact and its voltage should not vary appreciably during its use. There are mainly two types of batteries secondary batteries. primary batteries and In the primary batteries, the reaction occurs only once and after use over a period of time the battery becomes dead and cannot be reused again, whereas the secondary batteries are rechargeable. Production of electricity by thermal plants is not a very efficient method and is a major source of pollution. To solve this problem, galvanic cells are designed in such a way that energy of combustion of fuels is directly converted into electrical energy, and these are known as fuel cells. One such fuel cell was used in the Apollo space programme.
Answer the following questions :
Batteries and fuel cells are very useful forms of galvanic cell. Any battery or cell that we use as a source of electrical energy is basically a galvanic cell. However, for a battery to be of practical use it should be reasonably light, compact and its voltage should not vary appreciably during its use. There are mainly two types of batteries secondary batteries. primary batteries and In the primary batteries, the reaction occurs only once and after use over a period of time the battery becomes dead and cannot be reused again, whereas the secondary batteries are rechargeable. Production of electricity by thermal plants is not a very efficient method and is a major source of pollution. To solve this problem, galvanic cells are designed in such a way that energy of combustion of fuels is directly converted into electrical energy, and these are known as fuel cells. One such fuel cell was used in the Apollo space programme. Answer the following questions :
Batteries and fuel cells are very useful forms of galvanic cell. Any battery or cell that we use as a source of electrical energy is basically a galvanic cell. However, for a battery to be of practical use it should be reasonably light, compact and its voltage should not vary appreciably during its use. There are mainly two types of batteries secondary batteries. primary batteries and In the primary batteries, the reaction occurs only once and after use over a period of time the battery becomes dead and cannot be reused again, whereas the secondary batteries are rechargeable. Production of electricity by thermal plants is not a very efficient method and is a major source of pollution. To solve this problem, galvanic cells are designed in such a way that energy of combustion of fuels is directly converted into electrical energy, and these are known as fuel cells. One such fuel cell was used in the Apollo space programme. Answer the following questions :
Batteries and fuel cells are very useful forms of galvanic cell. Any battery or cell that we use as a source of electrical energy is basically a galvanic cell. However, for a battery to be of practical use it should be reasonably light, compact and its voltage should not vary appreciably during its use. There are mainly two types of batteries secondary batteries. primary batteries and In the primary batteries, the reaction occurs only once and after use over a period of time the battery becomes dead and cannot be reused again, whereas the secondary batteries are rechargeable. Production of electricity by thermal plants is not a very efficient method and is a major source of pollution. To solve this problem, galvanic cells are designed in such a way that energy of combustion of fuels is directly converted into electrical energy, and these are known as fuel cells. One such fuel cell was used in the Apollo space programme. Answer the following questions :
Batteries and fuel cells are very useful forms of galvanic cell. Any battery or cell that we use as a source of electrical energy is basically a galvanic cell. However, for a battery to be of practical use it should be reasonably light, compact and its voltage should not vary appreciably during its use. There are mainly two types of batteries secondary batteries. primary batteries and In the primary batteries, the reaction occurs only once and after use over a period of time the battery becomes dead and cannot be reused again, whereas the secondary batteries are rechargeable. Production of electricity by thermal plants is not a very efficient method and is a major source of pollution. To solve this problem, galvanic cells are designed in such a way that energy of combustion of fuels is directly converted into electrical energy, and these are known as fuel cells. One such fuel cell was used in the Apollo space programme. Answer the following questions :
Section B
Which one of the following first row transition elements is expected to have the highest third ionization enthalpy ?
Two among the three components of DNA are β-D-2-deoxyribose and a heterocyclic base. The third component is :
For an electrolyte undergoing association in a solvent, the vant factor :
The correct answer is 'is always less than one'. This is because when an electrolyte associates, the number of particles in solution decreases compared to the number expected based on the formula units, leading to a lower van 't Hoff factor (v) which is a measure of the degree of dissociation or association in the solution.
For the reaction X + 2Y → P, the differential form equation of the rate law is :
Acetic acid reacts with PCl₅ to give :
The formation of cyanohydrin from an aldehyde is an example of :
The correct answer is 'nucleophilic addition' because the reaction involves a nucleophile (cyanide ion) attacking the electrophilic carbonyl carbon of the aldehyde, leading to the formation of cyanohydrin.
The reaction of an alkyl halide with sodium alkoxide forming ether is known as :
The correct answer is Williamson synthesis. In Williamson synthesis, an alkyl halide reacts with a sodium alkoxide to produce an ether. This reaction is a common method for synthesizing ethers from alcohols and alkyl halides.
The correct order of the ease of dehydration of the following alcohols by the action of conc. H₂SO₄ is :
Which functional groups of glucose interact to form cyclic hemiacetal leading to pyranose structure ?
Assertion (A) : When NaCl is added to water a depression in freezing point is observed.
Reason (R) : NaCl undergoes dissociation in water.
Assertion (A) : Separation of Zr and Hf is difficult.
Reason (R) : Zr and Hf have similar radii due to lanthanoid contraction.
Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A). The similar ionic radii of Zr and Hf, resulting from the lanthanoid contraction, indeed make their separation challenging.
Assertion (A) : The pKₐ of ethanoic acid is lower than that of Cl -CH₂- COOH.
Reason (R) : Chlorine shows electron withdrawing ( I) effect which increases the acidic character of Cl -CH 2- COOH.
Assertion (A) is false, but Reason (R) is true. The pKₐ of Cl-CH₂-COOH is actually lower than that of ethanoic acid due to the electron-withdrawing effect of chlorine, which does increase the acidic character of Cl-CH₂-COOH. Therefore, while Reason (R) correctly describes the influence of chlorine on acidity, Assertion (A) is incorrect.
Assertion (A) : Aniline is a stronger base than ammonia.
Reason (R) : The unshared electron pair on nitrogen atom in aniline becomes less available for protonation due to resonance.
Which of the following compounds will give a ketone on oxidation with chromic anhydride (CrO₃) ?
Section C
Calculate the potential of Iron electrode in which the concentration of
Fe2+ ion is 0·01 M.
(E°Fe2+/Fe = 0·45 V at 298 K)
[Given : log 10 = 1]
E = E° - (0.0592 / n) * log [Fe2+]
Here, E° = 0.45 V, n = 2, and [Fe2+] = 0.01 M
So, E = 0.45 - (0.0592 / 2) * log 0.01
= 0.45 - 0.0296 * (-2) since log 0.01 = -2
= 0.45 + 0.0592
= 0.5092 V
Therefore, the potential of the iron electrode is approximately 0.51 V.
Define molecularity of the reaction. State any one condition in which a bimolecular reaction may be kinetically of first order
(b) Condition when a bimolecular reaction is kinetically first order: If one reactant is in large excess so that its concentration remains nearly constant during the reaction, the rate depends effectively only on the concentration of the other reactant. Thus, the reaction appears to follow first order kinetics even though it is bimolecular in molecularity.
Other Years — CHEMISTRY