Lecture Notes on D and F Block Elements

Introduction

• Discussion on questions involving D and F block elements.
• Focus on reactions with H2S and oxidizing agents such as KMnO4 and K2Cr2O7.

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Reactivity of H2S with Oxidizing Agents

Question 1: H2S with KMnO4

• H2S acts as a reducing agent.
• KMnO4 acts as an oxidizing agent in acidic medium.
  • Reaction:
    • Oxidation: H2S → S + 2H+ + 2e-
    • Reduction: MnO4- + 8H+ + 5e- → Mn2+ + 4H2O
• For 5 moles of H2S:
  • Water produced (X) = 8 moles
  • Electrons transferred (Y) = 10 moles
  • Result: X + Y = 18

Question 2: H2S with K2Cr2O7

• Oxidation: H2S → S + 2H+ + 2e-
• Reduction: Cr2O7^2- + 14H+ + 6e- → 2Cr3+ + 7H2O
• Calculation for 5 moles of H2S:
  • Water produced (X) = 35/3 moles
  • Electrons transferred (Y) = 10 moles
  • Result: X + Y = 65/3 ≈ 22

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Magnetic Moment of Manganese Compounds

Question 3: Strongest Oxidizing Ability

• Compare:
  • MnF4 (Mn +4): 3d3
  • MnF3 (Mn +3): 3d4 (strongest oxidizing agent)
  • MnF2 (Mn +2): 3d5
• Magnetic Moment Calculation:
  • \( u = ext{√(N(N+2))} \)
  • For Mn3+: N = 4; (\mu = \text{√(4(4+2))} = \text{√(24)} = 4.9 \text{ Bohr Magnetons}

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Redox Reactions and Conversions

Question 4: I- to I2 Conversion

• Total number of reagents that can convert I- to I2:
  • Acidified KMnO4, alkaline KMnO4, CuSO4, H2O2, Cl2, O3, FeCl3, HNO3, Na2S2O3
  • Excluded: Alkaline KMnO4 and Na2S2O3 (reducing agent)
• Net Redox Reaction Examples:
  • MnO4- → Mn2+ + 4H2O
  • Cu2+ + I- → CuI + I2

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Summary of Key Redox Reactions

Examples:

• Permanganate: Reducing agents and their reactions:
  • H2O2 forms H2O as oxidizing agent.
  • I- gives I2 + 2e-
• Copper Reactions:
  • Reacts with I- and produces I2 and CuI.
• Oxalate Reaction with KMnO4:
  • 225 mg of oxalic acid reacts with KMnO4; stoichiometry for determining weight percentages.

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Additional Notes

Characteristics of Periodic Elements

• Importance of ionic configurations and oxidation states in understanding reactivity and stability.
• Lanthanides and actinides discussed regarding electronic configurations and oxidation states.

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Conclusion

• The lecture emphasized the significance of redox reactions in D and F block elements.
• Students encouraged to practice balancing redox reactions and understanding the implications of electron transfer in chemical reactions.