Class 12 Chemistry MID Term Examination 2024 set 1

Class 12 Chemistry MID Term  Examination 2024 

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 (Numerical and Theory)
• Section C: 3-mark questions (Numerical and Theory)
• Section D: 5-mark long-answer and comprehension questions
• 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 molarity of a solution is defined as the number of moles of solute per __________.
   • 1. Liter of solvent
   • 2. Liter of solution
   • 3. Kilogram of solvent
   • 4. Kilogram of solution
2. Which of the following is a colligative property?
   • 1. Boiling point
   • 2. Osmotic pressure
   • 3. Surface tension
   • 4. Viscosity
3. In an electrochemical cell, electrons flow from:
   • 1. Anode to cathode
   • 2. Cathode to anode
   • 3. Both ways
   • 4. None of the above
4. The rate constant of a reaction depends on:
   • 1. Temperature
   • 2. Concentration
   • 3. Time
   • 4. Reaction order
5. Transition metals exhibit variable oxidation states due to:
   • 1. High ionization energy
   • 2. Availability of d orbitals
   • 3. Inert pair effect
   • 4. Large atomic size
6. In a first-order reaction, the half-life is directly proportional to:
   • 1. Concentration
   • 2. Temperature
   • 3. Rate constant
   • 4. None of these
7. The activation energy of a reaction is:
   • 1. Independent of temperature
   • 2. Decreased by a catalyst
   • 3. Increased by a catalyst
   • 4. Not required for exothermic reactions
8. The standard reduction potential of a substance indicates its tendency to:
   • 1. Gain electrons
   • 2. Lose electrons
   • 3. Remain neutral
   • 4. Form covalent bonds
9. Which of the following elements does not exhibit variable oxidation states?
   • 1. Scandium
   • 2. Chromium
   • 3. Copper
   • 4. Zinc
10. Colligative properties depend on:
    • 1. The nature of the solute particles
    • 2. The number of solute particles
    • 3. The nature of the solvent
    • 4. None of these
11. In the extraction of copper, FeSiO₃ is produced as:
    • 1. Slag
    • 2. Flux
    • 3. Alloy
    • 4. Ore
12. The rate of a reaction quadruples when the temperature increases from 300 K to 320 K. The reaction follows:
    • 1. Zero-order kinetics
    • 2. First-order kinetics
    • 3. Second-order kinetics
    • 4. None of the above
13. Which one of the following is not an alloy?
    • 1. Brass
    • 2. Bronze
    • 3. Steel
    • 4. Zinc
14. In a galvanic cell, the anode is:
    • 1. Positively charged
    • 2. Negatively charged
    • 3. Neutral
    • 4. None of these
15. The entropy of the universe:
    • 1. Always increases
    • 2. Always decreases
    • 3. Remains constant
    • 4. Is zero

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

16. Calculate the molarity of a solution containing 10 g of NaOH in 500 mL of solution. 
17. Derive the relation between molar conductivity and conductivity for a weak electrolyte. 
18. Write the Nernst equation for the electrochemical cell:
    Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)
    OR
    Calculate the EMF of the cell at 25°C if [Zn²⁺] = 0.1 M and [Cu²⁺] = 0.01 M. (Numerical)
19. Explain the role of adsorption in heterogeneous catalysis. 
20. Calculate the boiling point elevation when 10 g of glucose (C₆H₁₂O₆) is dissolved in 100 g of water. The molal boiling point elevation constant for water is 0.52 K kg/mol. 
21. Define the rate constant and explain how it is related to the order of a reaction. 
22. What is the crystal field theory and how does it explain the color of transition metal complexes? 
23. Define colligative properties. Why is osmotic pressure considered a colligative property? 
24. Calculate the standard Gibbs free energy change (ΔG°) for the reaction at 298 K:
    Zn(s) + 2H⁺(aq) → Zn²⁺(aq) + H₂(g)
    Given: ΔH° = –150 kJ/mol, ΔS° = 50 J/mol·K. (Numerical)
    OR
    Explain how entropy plays a role in determining spontaneity of reactions. (Theory)
25. Discuss the trend of ionization enthalpy across the d-block elements. 
26. Explain the role of zinc in the extraction of silver by cyanide process. 
27. State Raoult’s law for ideal solutions and explain its significance. 
28. Define ligand and give two examples of bidentate ligands. 
29. Explain the effect of temperature on the rate of reaction according to the Arrhenius equation. 

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

30. The rate of a reaction quadruples when the temperature increases from 300 K to 320 K. Calculate the activation energy assuming the temperature dependence of the rate constant follows the Arrhenius equation. (Numerical)
    OR
    Explain the relationship between temperature and reaction rate based on the Arrhenius equation. 
31. Define the crystal field splitting energy and explain its significance in the color of transition metal complexes. 
    OR
    Discuss the role of crystal field theory in determining the magnetic properties of coordination compounds. (Theory)
32. Explain the process of ion exchange in the softening of hard water. 
    OR
    Describe the use of ion-exchange resins in the removal of hardness from water. (Theory)
33. Describe the mechanism of enzyme catalysis. How do enzymes affect the rate of biochemical reactions? 
    OR
    Explain how the Michaelis-Menten equation describes enzyme kinetics. 

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

34. Write the chemical equations for the extraction of copper from its ores and describe the principle behind each step involved. 
    OR
    Explain the extraction of aluminium from bauxite using the Hall-Héroult process. 
35. Explain the working of a galvanic cell and derive the Nernst equation. Give an example of a practical application of a galvanic cell. 
    OR
    Describe the electrochemical series and explain its significance in predicting the feasibility of a redox reaction. 

Comprehension

Read the following passage and answer the questions that follow:

"Enzymes are biological catalysts. Most enzymes are proteins, and their function is to speed up chemical reactions in the body. They work by lowering the activation energy required for a reaction to occur. Each enzyme is specific to a particular substrate, meaning that an enzyme only catalyzes a specific type of reaction. The enzyme's activity can be affected by various factors, such as pH, temperature, and the concentration of the substrate."

1. What is the primary function of enzymes in the body?
2. How do enzymes lower the activation energy of a reaction?
3. What type of molecule are most enzymes?
4. What factors can affect enzyme activity?
5. What does it mean when an enzyme is specific to a substrate?