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ChemistryClass 12English

CBSE Chemistry Class 12 Paper 2 Sample 2023

Electrochemistry and kinetics questions in CBSE exams often trip students who confuse cell potential with free energy, or confuse reaction order with molecularity — but understanding these distinctions is the gateway to predicting redox mechanisms and exam stability marks. This sample covers electrode potentials, Gibbs energy, rate laws, and coordination compound stability across authentic MCQ, true/false, and fill-in formats. You'll find the same depth and pacing as the real 2023 board paper, with emphasis on conceptual reasoning over rote calculation. After working through these 15 questions, you'll be able to spot when a reaction is spontaneous without a calculator, and explain why a first-order rate law looks the way it does in a multi-step mechanism.

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  1. Question 1

    A galvanic cell is constructed with zinc and copper electrodes. The standard electrode potentials are E°(Zn2+/Zn)=−0.76E°(Zn^{2+}/Zn) = -0.76 V and E°(Cu2+/Cu)=+0.34E°(Cu^{2+}/Cu) = +0.34 V. What is the standard cell potential (E°cellE°_{cell}) for this cell?

  2. Question 2

    Using the data from the previous question, what is the Gibbs free energy change (ΔG°ΔG°) for the spontaneous reaction at 25°C? (Use F=96500F = 96500 C/mol, R=8.314R = 8.314 J/(mol·K), and the relationship ΔG°=−nFE°cellΔG° = -nFE°_{cell}.)

  3. Question 3

    The Nernst equation at 25°C is Ecell=E°cell−0.0592nlog⁡QE_{cell} = E°_{cell} - \frac{0.0592}{n} \log Q. In a concentration cell with Cu electrodes, if the concentration of Cu²⁺ at the cathode is 1.0 M and at the anode is 0.01 M, what is the cell potential? (n = 2)

  4. Question 4

    True or False: In an electrolytic cell, the anode is always the negative electrode.

  5. Question 5

    A reaction has the rate law: rate=k[A]2[B]rate = k[A]^2[B]. The overall order of this reaction is ____.

  6. Question 6

    The half-life of a first-order reaction is 50 minutes. How much of the reactant remains after 150 minutes?

  7. Question 7

    A reaction proceeds in two steps: Step 1 (slow): A + B → AB. Step 2 (fast): AB + C → D. The rate law derived from this mechanism is rate=k[A][B]rate = k[A][B]. Which species is an intermediate?

  8. Question 8

    True or False: Molecularity and order of reaction are always the same.

  9. Question 9

    In the complex ion [Fe(CN)6]4−[Fe(CN)_6]^{4-}, the coordination number of Fe is ____.

  10. Question 10

    Which of the following complexes is expected to be coloured in solution?

  11. Question 11

    In crystal field theory, the energy splitting between dxyd_{xy} and dz2d_{z^2} orbitals in an octahedral field is denoted by the parameter ____.

  12. Question 12

    The magnetic moment of a transition metal complex depends on the number of unpaired electrons. For a high-spin [Fe(H2O)6]3+[Fe(H_2O)_6]^{3+} complex, the number of unpaired electrons is ____.

  13. Question 13

    Increasing the concentration of a complex ion increases its stability constant. True or False?

  14. Question 14

    A complex with geometry X has a crystal field stabilization energy (CFSE) where the dx2−y2d_{x^2-y^2} orbital is the highest in energy. What is the most likely geometry?