Hich is true about the dissolving process in water?
A Polar solutes do not dissolve easily in water.
B Water molecules are attracted by solute ions at the surface of the solute.
C Water molecules move throughout the solute.
D Solute molecules pull water molecules away from the surface.
The Correct Answer and Explanation is :
The correct answer is B: Water molecules are attracted by solute ions at the surface of the solute.
Explanation
The dissolving process, particularly with polar solutes in water, is a fascinating example of molecular interactions. Water is a polar solvent, meaning it has a partial positive charge on one side (the hydrogen atoms) and a partial negative charge on the other (the oxygen atom). This polarity allows water molecules to interact strongly with other polar substances or ionic compounds (solutes).
When a polar solute, such as table salt (NaCl), is introduced to water, the process of dissolution begins. Water molecules approach the surface of the solute and form interactions with the solute’s ions. In the case of NaCl, the positively charged sodium ions (Na⁺) are attracted to the partial negative charge of the oxygen atom in water, while the negatively charged chloride ions (Cl⁻) are attracted to the partial positive charges of the hydrogen atoms in water. This attraction causes the water molecules to cluster around the solute ions, effectively pulling them away from the solid structure of the solute.
As this process continues, water molecules surround the individual solute ions, a phenomenon known as solvation. The energy released during the solvation process compensates for the energy needed to break the ionic bonds in the solute, allowing it to dissolve in water. The movement of water molecules throughout the solute is not as accurate as stating that they are specifically attracted to solute ions at the surface (option B).
Other options (A, C, and D) are incorrect because polar solutes do dissolve easily in water due to strong interactions, water does not simply move throughout the solute without interacting first, and while solute molecules interact with water, the primary driving force is the attraction between water molecules and solute ions rather than the solute pulling water molecules away. Thus, option B accurately captures the essence of the dissolving process in water.