Final answer:
Water weakens the electrostatic interaction of ions as its polar molecules solvate and disperse the ions in solution, reducing their interaction and allowing them to move freely.
Step-by-step explanation:
Water weakens the electrostatic interaction of ions due to its properties as a polar solvent with strong ion-dipole interactions. When ionic compounds like KCl are dissolved in water, the water molecules use their polar nature to surround and solvate the ions. This hydration shell significantly reduces the electrostatic forces that hold the ions together in the solid state. As a result, the ions are freed to move independently in solution, which is crucial for processes like electrical conductivity in biological systems and the dissolution of ionic compounds.
The dissolution process leads to an increase in disorder as ions transition from a fixed position in a crystal lattice to a mobile state in solution. According to the Debye-Hückel theory, solvation reduces but does not completely eliminate interionic attraction, affecting the activity of ions. In very dilute solutions, the effective concentrations of ions (activities) approximate the actual concentrations.