Class 12 Chemistry Mid Term Sample Paper Set 3

Class 12 Chemistry Mid Term Sample question paper (High Standard)

Maximum Marks: 70

Time Allowed: 3 Hours

General Instructions:

• All questions are compulsory.
• The question paper consists of 4 sections:
• Section A: 1-mark questions (MCQs)
• Section B: 2-mark questions (Theory and Numerical)
• Section C: 3-mark questions (Theory and Numerical)
• Section D: 5-mark long-answer questions and comprehension.
• Internal choices are provided for selected questions.
• Use of a scientific calculator is not allowed.
• Diagrams should be neat and labeled appropriately wherever necessary.

Section A: MCQs (1 Mark Each) [Total: 15 Marks]

1. The oxidation state of nitrogen in NH₄⁺ is:
   • 1. -3
   • 2. -2
   • 3. -1
   • 4. +3
2. Which of the following metals is extracted by the Mond process?
   • 1. Nickel
   • 2. Copper
   • 3. Aluminium
   • 4. Iron
3. What is the shape of SF₆ molecule according to VSEPR theory?
   • 1. Tetrahedral
   • 2. Octahedral
   • 3. Trigonal Bipyramidal
   • 4. Square Planar
4. The role of a salt bridge in an electrochemical cell is to:
   • 1. Complete the circuit and allow current to flow
   • 2. Maintain electrical neutrality
   • 3. Transport electrons
   • 4. Store potential energy
5. The rate of reaction is fastest when:
   • 1. The concentration of reactants is high
   • 2. The concentration of reactants is low
   • 3. The reaction is at equilibrium
   • 4. The activation energy is high
6. In the extraction of aluminium, which compound is used as a flux?
   • 1. CaO
   • 2. Na₂CO₃
   • 3. Cryolite
   • 4. Al₂O₃
7. The entropy of a perfectly crystalline substance at 0 K is:
   • 1. 0
   • 2. 1
   • 3. Infinite
   • 4. -1
8. Which one of the following is a weak electrolyte?
   • 1. NaCl
   • 2. HCl
   • 3. CH₃COOH
   • 4. KOH
9. The equilibrium constant for a reaction is related to the Gibbs free energy change (ΔG) as:
   • 1. ΔG = -RT ln K
   • 2. ΔG = RT ln K
   • 3. ΔG = R ln K
   • 4. ΔG = -R ln K
10. Which of the following is an example of a coordination compound?
    • 1. K₄[Fe(CN)₆]
    • 2. NaCl
    • 3. H₂SO₄
    • 4. NH₃
11. In the chlor-alkali process, chlorine gas is produced at the:
    • 1. Cathode
    • 2. Anode
    • 3. Salt Bridge
    • 4. Both Cathode and Anode
12. The magnetic moment of [NiCl₄]²⁻ (tetrahedral) is:
    • 1. Zero
    • 2. 2.83 BM
    • 3. 3.87 BM
    • 4. 1.73 BM
13. What is the primary product in the hydration of ethene (C₂H₄)?
    • 1. Methanol
    • 2. Ethanol
    • 3. Acetone
    • 4. Ethanoic acid
14. The gas law that relates pressure and volume at constant temperature is:
    • 1. Boyle's law
    • 2. Charles' law
    • 3. Avogadro's law
    • 4. Ideal gas law
15. The number of π bonds in benzene is:
    • 1. 6
    • 2. 3
    • 3. 12
    • 4. 1

Section B: 2 Marks Each [Total: 28 Marks]

16. Derive the relation between free energy change (ΔG) and equilibrium constant (K).
    OR
    Explain Le Chatelier’s principle with an example.
17. Write the electronic configuration of Fe³⁺.
18. Calculate the molarity of a solution containing 36.5 g of HCl in 500 mL of solution. (Numerical)
19. Differentiate between adsorption and absorption with examples.
20. Explain the term "collision theory of reaction rates."
    OR
    Define the "rate-determining step" in a chemical reaction.
21. Write the Nernst equation for a cell reaction and explain its significance.
22. Calculate the pH of a solution with a hydrogen ion concentration of 1 x 10⁻³ M. (Numerical)
23. Define colligative properties. Explain any one of them.
    OR
    Define molal depression constant (Kf) and state its significance.
24. Calculate the number of moles of NaOH required to neutralize 50 mL of 1 M H₂SO₄. (Numerical)
25. Write the structural formula of ethanal and propanone.
26. Define standard electrode potential and its importance in electrochemical cells.
27. What are homogeneous and heterogeneous catalysis? Explain with examples.
    OR
    Write a note on enzyme catalysis.
28. Calculate the oxidation state of chromium in K₂Cr₂O₇. (Numerical)
29. Explain the concept of resonance with reference to benzene.

Section C: 3 Marks Each [Total: 12 Marks]

30. Explain the mechanism of SN1 and SN2 reactions with suitable examples.
    OR
    Discuss the role of a catalyst in increasing the rate of a chemical reaction.
31. Define the common ion effect and its applications in qualitative analysis.
32. Differentiate between cis and trans isomers with examples.
    OR
    Explain geometrical isomerism in alkenes.
33. Explain the significance of the Van't Hoff factor (i) in calculating colligative properties.

Section D: 5 Marks Each [Total: 10 Marks]

34. Describe the extraction of zinc from zinc blende (ZnS).
    OR
    Explain the extraction of iron from haematite using a blast furnace.
35. Explain the electrolysis of brine solution. What are the products formed at each electrode?
    OR
    Write the mechanism for the acid-catalyzed dehydration of ethanol to ethene.

Comprehension [Total: 5 Marks]

Read the following passage and answer the questions that follow:

"Proteins are complex biomolecules made up of amino acids. They serve as structural materials, enzymes, and antibodies in living organisms. Proteins are unique due to their ability to fold into specific three-dimensional shapes, allowing them to carry out diverse functions. The primary structure of a protein is its amino acid sequence, while the higher-order structures include secondary, tertiary, and quaternary levels. The shape and function of a protein can be affected by factors such as pH, temperature, and the presence of inhibitors."

1. What are proteins made of? (1 mark)
2. Name one function of proteins in the human body. (1 mark)
3. What determines the primary structure of a protein? (1 mark)
4. How can temperature affect a protein’s structure? (1 mark)
5. What is a protein inhibitor? (1 mark)