Solid potassium permanganate, KMnO4, is much more soluble in water than in hexane (C6H14). Which one of the following is primarily responsible for the greater solubility of KMnO4 in water than in hexane? ionic bonding B. ion-dipole forces C. London dispersion forces D. dipole-dipole forces E. the molecular weight of the solvent.
The Correct Answer and Explanation is :
The correct answer is B. ion-dipole forces.
Explanation:
Potassium permanganate (KMnO4) is an ionic compound, meaning that it consists of positively charged potassium ions (K⁺) and negatively charged permanganate ions (MnO₄⁻). When KMnO4 is added to water, the ions dissociate and interact with the water molecules.
Water is a polar solvent, meaning that it has a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom. This makes water capable of interacting with charged species, such as ions, through ion-dipole interactions. These interactions occur when the charged ions (like K⁺ and MnO₄⁻) are surrounded by water molecules, with the negative end of water molecules (oxygen) attracting the positive potassium ions and the positive end of water molecules (hydrogens) attracting the negative permanganate ions. The ion-dipole interactions are strong enough to overcome the electrostatic forces holding the ions together in the solid KMnO4, allowing it to dissolve readily in water.
In contrast, hexane (C₆H₁₄) is a nonpolar solvent. It lacks the ability to form strong interactions with the ions in KMnO4. The only intermolecular force present in hexane is London dispersion forces, which are weak, transient attractions between nonpolar molecules. These forces are not strong enough to break apart the ionic bonds in KMnO4 and facilitate its dissolution.
Therefore, the reason KMnO4 is much more soluble in water than in hexane is primarily due to the ion-dipole forces between the ions in KMnO4 and the polar water molecules. These forces are much stronger than the London dispersion forces present in hexane, leading to greater solubility in water.