PUNJAB BOARD CLASS 12 CHEMISTRY PAPER PDF ANSWER KEY 2025

PUNJAB BOARD CLASS 12 CHEMISTRY PAPER ANSWER KEY 2025

 

Class 12 Biology & Chemistry Question Paper with Answers

Instructions:

• You must write the subject code (paper-code: 053) in the box provided on the title page of your answer book.
• Make sure that the answer book contains 32 pages (including title page) and is properly intact.
• Questions 1-5 are very short-answer type questions carrying one mark each.
• Questions 6-21 are short-answer type questions carrying two marks each.
• Questions 22-25 are long-answer type questions carrying three marks each.
• Questions 26-30 are very long-answer type questions carrying five marks each.
• All questions are compulsory.
• There will be internal choices in two-mark, three-mark, and five-mark questions.
• The English version of the question is considered correct in case of any confusion.

Question Paper:

1. Read the following paragraph and answer the questions given below:

It has been observed that nucleus of a living cell is responsible for the transmission of inherent characters, so-called heredity. The purines, sugar, and phosphoric acid react chemically with the product and absorbance type of behavior and called nucleic acids. These are mainly of two types, the deoxyribonucleic acids (DNA) and ribonucleic acids (RNA). These are thread-like macromolecules. DNA molecules are long chain types and they perform duty as genes, so they are called polynucleotides. RNA molecules are of three types and they perform different functions. They are named as messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).

Questions:

1. Give full form of DNA and RNA.
2. How many types of RNA are there?
3. How many types of nucleic acids are there?
4. Define heredity.
5. Who is responsible for heredity?

2. True/False:

1. CO is a stronger ligand than Cl⁻. True
2. The colour produced in Victor Meyer test for primary alcohol is deep blue. False
3. Formic acid is obtained from red ants. True

Answers:

1. Read the paragraph and answer:

1. Full form of DNA and RNA: DNA - Deoxyribonucleic Acid, RNA - Ribonucleic Acid.
2. Types of RNA: There are three types of RNA - Messenger RNA (mRNA), Ribosomal RNA (rRNA), and Transfer RNA (tRNA).
3. Types of nucleic acids: There are two types - DNA and RNA.
4. Definition of heredity: Heredity is the transmission of genetic characteristics from parents to offspring through DNA.
5. Who is responsible for heredity? DNA is responsible for heredity.

2. True/False:

1. CO is a stronger ligand than Cl⁻. True
2. The colour produced in Victor Meyer test for primary alcohol is deep blue. False
3. Formic acid is obtained from red ants. True

Class 12 Chemistry Multiple Choice Questions with Answers

Multiple Choice Questions:

1. IUPAC name of Acetone is:
   • (a) Butanone
   • (b) Propanone (✔ Correct Answer)
   • (c) Pentanone
   • (d) Ethanol
2. Ni(CO)₄ is diamagnetic because:
   • (a) It has unpaired electrons
   • (b) It has paired electrons (✔ Correct Answer)
   • (c) It has an odd number of electrons
   • (d) None of these
3. The units of ebulloscopic constant is:
   • (a) K kg mol⁻¹(✔ Correct Answer)
   • (b) mol kg⁻¹
   • (c) kg mol⁻¹ K⁻¹
   • (d) K mol kg⁻¹
4. Galvanisation is applying a coating of:
   • (a) Cu
   • (b) Cr
   • (c) Zn (✔ Correct Answer)
   • (d) Pb
5. The unit of first-order reaction rate constant is:
   • (a) mol L⁻¹ s⁻¹
   • (b) s⁻¹ (✔ Correct Answer)
   • (c) L⁻¹ s⁻¹
   • (d) mol L⁻¹
6. The mole fraction of benzene in a solution containing 30% by mass in carbon tetrachloride is:
   • (a) 0.540
   • (b) 0.459 (✔ Correct Answer)
   • (c) 0.500
   • (d) 0.300
7. The porous membrane used in reverse osmosis plant is made up of:
   • (a) Potassium nitrate
   • (b) Starch nitrate
   • (c) Cellulose acetate (✔ Correct Answer)
   • (d) Mercuric iodide
8. What is DDT among the following?
   • (a) Fertilizer
   • (b) Degradable pollutant
   • (c) Non-biodegradable pollutant (✔ Correct Answer)
   • (d) Greenhouse gas
9. In the following, the strongest acid is:
   • (a) CH₃COOH
   • (b) C₆H₅COOH (✔ Correct Answer)
   • (c) C₂H₅COOH
   • (d) HCOOH
10. Benzoic acid reacts with LiAlH₄ to give:
    • (a) Ethane
    • (b) Methyl benzene
    • (c) Benzyl alcohol (✔ Correct Answer)
    • (d) Phenol
11. Vinegar is a dilute aqueous solution of:
    • (a) Citric acid
    • (b) Benzoic acid
    • (c) Oxalic acid
    • (d) Acetic acid (✔ Correct Answer)
12. The oxidation state of Fe in [Fe(CN)₆]^3- is:
    • (a) +2
    • (b) +3 (✔ Correct Answer)
    • (c) +4
    • (d) -3

Two Mark Questions

1. Write two differences between double salt and coordination compounds.
2. Give two differences between ideal and non-ideal solutions.
3. Define monodentate ligands and give an example.
4. Why do alcohols have a higher boiling point than haloalkanes of the same molecular mass?
5. How will you convert propan-1-ol to propan-2-ol?
6. Describe Rosenmund reduction. OR
7. Lower carboxylic acids are highly soluble in water. Explain.
8. How will you obtain chlorobenzene from aniline?
9. Give two differences between DNA and RNA.
10. Calculate the molal elevation constant of water if a 0.1 molal aqueous solution of a substance boils at 100.052°C.
11. 1.8 gm of glucose (C₆H₁₂O₆) is dissolved in 1 kg of water in a saucepan. At what temperature will the water boil at 1.013 bar pressure? (K_b for water is 0.52 K kg mol^-1)
12. Give two differences between Galvanic Cell and Electrolytic Cell.
13. How many Coulombs of electricity are required for the complete oxidation of 50 gm of H₂O?
14. Give two differences between the order of reaction and the molecularity of reaction.

Three Mark Questions

1. The rate constant for a first-order reaction (k) is 60 sec^-1. How much time will it take to reduce the concentration of the reaction to 1/10^th of its initial value?
2. Calculate the half-life time of a first-order reaction having k = 8 min^-1.
3. Why do Zr and Hf exhibit similar properties?
4. Calculate the two-third life of a first-order reaction having k = 5.48 × 10^-4 s^-1.
5. Compare the acidic character of Primary, Secondary, and Tertiary alcohols. OR
6. Explain the Reimer-Tiemann reaction of Phenols.

Five Mark Questions

1. Why is aniline less basic than ethylamine?
2. Calculate the molar conductance (Λ_m) for CaCl₂ given that Λ⁰ (Ca²⁺) = 119.5 S cm² mol^-1 and Λ⁰ (Cl^-) = 76.3 S cm² mol^-1. OR
3. Write the Nernst equation and calculate the emf of the following cell at 298K:
   Fe(s) | Fe²⁺ (0.001M) || H⁺ (1M) | H₂(atm) | Pt.
   Given E° (Fe²⁺/Fe) = -0.44 V
4. Write the reaction for:
   
   1. Wurtz-Fittig reaction
   2. Ullmann reaction
   3. Gattermann reaction
   4. Hunsdiecker reaction
   5. Balz-Schiemann reaction

Five Mark Questions

1. Write four differences between S_N2 (substitution nucleophilic bimolecular reaction) and S_N1 (substitution nucleophilic unimolecular reaction). (4+1=5)

Three Mark Questions

1. Define Optical activity.
2. Give the following:
   
   1. Three differences between Lanthanoids and Actinoids.
   2. Explain why Cu²⁺ salts are coloured while Zn²⁺ salts are colourless? OR
   3. Why do transition metals form alloys with other metals? Explain.
3. How many unpaired electrons are present in Fe³⁺, Zn²⁺, and Mn²⁺?

PUNJAB BOARD CLASS 12 CHEMISTRY PAPER PDF 2025