Solvation with Water as the Solvent
- When you add sugar to your tea, the sugar disappears, leaving a sweet solution.
- This process, called solvation, is driven by the unique properties of water.
Definition
Solvation
Solvation is the process where solvent molecules surround and interact with solute particles, stabilizing them in solution.
Water Is a Good Solvent Because of Its Polarity and Hydrogen Bonding
1. Polarity of Water
- Water molecules have a bent shape, with oxygen at one end and hydrogen atoms at the other.
- Oxygen is more electronegative than hydrogen, meaning it pulls shared electrons closer to itself.
- This creates a partial negative charge ($\delta^-$) near the oxygen atom and a partial positive charge ($\delta^+$) near the hydrogen atoms.
Think of a water molecule as a tiny magnet, with one end slightly negative and the other slightly positive.
2. Hydrogen Bonding
- The partial charges in water molecules allow them to form hydrogen bonds:
- The $\delta^+$ hydrogen of one water molecule is attracted to the $\delta^-$ oxygen of another.
- When sodium chloride (NaCl) dissolves in water, the Na+ ions are surrounded by the partially negative oxygen ends of water molecules.
- On the other hand, the Cl- ions are surrounded by the partially positive hydrogen ends.
Solvation Depends on The Nature of The Solute
- These interactions depend on the nature of the solute: ionic or polar.
Solvation of Ionic Compounds
- Ionic compounds, like NaCl, are made of positively charged cations (e.g., Na⁺) and negatively charged anions (e.g., Cl⁻).
- When NaCl is added to water:
- Water molecules surround the ions.
- The partial negative charge of oxygen is attracted to Na⁺.
- The partial positive charge of hydrogen is attracted to Cl⁻.
