Which of the following is arranged in decreasing order of ionic mobility?

The correct answer is F^- → Cl^- → Br^- → I^-.

Key Points

• Ionic mobility refers to the speed at which an ion moves through a solvent under the influence of an electric field.
• Ionic mobility generally decreases with an increase in the size of the ion. Smaller ions move faster because they experience less resistance in the solvent.
• Among halide ions (F^-, Cl^-, Br^-, I^-), fluoride (F^-) has the highest ionic mobility, followed by chloride (Cl^-), bromide (Br^-), and iodide (I^-).
• The decreasing order of ionic mobility for halide ions is F^- → Cl^- → Br^- → I^-.

Additional Information

• Ionic Mobility:
  • Ionic mobility is influenced by factors such as ionic size, charge, and the viscosity of the solvent.
  • In an electric field, ions migrate towards the electrode of opposite charge, and their mobility is measured as the velocity per unit electric field strength.
• Hydration Energy:
  • Hydration energy is the amount of energy released when an ion is surrounded by water molecules.
  • Smaller ions like F^- have higher hydration energy, which enhances their mobility in an aqueous solution.
• Viscosity of Solvent:
  • The viscosity of the solvent affects the ionic mobility. Higher viscosity results in lower ionic mobility due to increased resistance.
  • Water, having low viscosity, is a common solvent used in studies of ionic mobility.
• Electrophoresis:
  • Electrophoresis is a technique used to separate ions based on their mobility under an electric field.
  • This method is widely used in biochemical analysis to separate proteins, nucleic acids, and other charged particles.