Solid, potassium permanganate, KMnO4, is much more soluble in water than in CH2Cl2 (a non-polar solvent). Which of the following intermolecular forces is primarily responsible for the greater solubility of KMnO4 in water than in CH2Cl2? O dipole-dipole forces London dispersion forces hydrogen bonding ion-dipole forces ionic bonding
The Correct Answer and Explanation is :
The correct answer is ion-dipole forces.
Explanation:
Potassium permanganate (KMnO₄) is an ionic compound, consisting of potassium ions (K⁺) and permanganate ions (MnO₄⁻). The solubility of ionic compounds like KMnO₄ in solvents depends on the interactions between the ions in the compound and the solvent molecules.
- Water as a solvent: Water is a highly polar solvent, with a strong ability to form hydrogen bonds due to the electronegativity of oxygen. When KMnO₄ is added to water, the polar water molecules surround the K⁺ and MnO₄⁻ ions, forming ion-dipole interactions. The positively charged potassium ion is attracted to the partial negative charge of the oxygen in water molecules, and the negatively charged permanganate ion is attracted to the partial positive charge of the hydrogen atoms in water. These ion-dipole forces are strong and effectively break the ionic bonds in KMnO₄, allowing the compound to dissolve.
- CH₂Cl₂ (dichloromethane) as a solvent: CH₂Cl₂ is a non-polar solvent, which has weaker intermolecular forces compared to water. It primarily experiences London dispersion forces, which are much weaker than ion-dipole forces. Non-polar solvents cannot effectively interact with the K⁺ and MnO₄⁻ ions in KMnO₄, meaning that KMnO₄ will not dissolve well in CH₂Cl₂.
Conclusion: The greater solubility of KMnO₄ in water compared to CH₂Cl₂ is due to the strong ion-dipole interactions between the ions of KMnO₄ and the polar water molecules. These interactions are significantly stronger than the London dispersion forces that would operate in CH₂Cl₂, leading to a greater solubility in water.