Match the following compounds to their likely solubility in water: -KI -Cl2 -C2H5OH
The Correct Answer and Explanation is:
Correct Matching of Compounds to Their Likely Solubility in Water:
- KI – Soluble
- Cl₂ (Chlorine gas) – Insoluble (Slightly soluble)
- C₂H₅OH (Ethanol) – Soluble
Explanation (Approx. 300 words):
Water is a polar solvent, meaning it has molecules with partial positive and negative charges due to its bent structure and the electronegativity difference between hydrogen and oxygen. The general rule for solubility is “like dissolves like”—polar substances tend to dissolve in polar solvents, and nonpolar substances dissolve in nonpolar solvents.
1. Potassium Iodide (KI): Soluble
KI is an ionic compound, composed of K⁺ and I⁻ ions. Ionic compounds generally dissolve well in water because the polar water molecules surround and stabilize the individual ions through a process called hydration. The partial negative end (oxygen) of water is attracted to K⁺, and the partial positive end (hydrogen) is attracted to I⁻. This effectively pulls the crystal lattice apart, making KI highly soluble in water.
2. Chlorine (Cl₂): Slightly Soluble
Cl₂ is a nonpolar covalent molecule, composed of two identical chlorine atoms sharing electrons equally. Since water is polar and Cl₂ is nonpolar, there are minimal intermolecular interactions between them. Cl₂ has very limited solubility in water (approximately 0.7 g/L at 20°C), and it only dissolves to a small extent due to physical dispersion and minor chemical reactions (e.g., forming hypochlorous acid). Therefore, it’s classified as insoluble or only slightly soluble in water.
3. Ethanol (C₂H₅OH): Soluble
Ethanol contains a polar hydroxyl group (-OH) which can form hydrogen bonds with water molecules. Although the ethyl group (C₂H₅–) is nonpolar, it is small enough that the overall molecule remains highly soluble in water. This balance makes ethanol miscible with water, meaning it can mix in any proportion.
Thus, based on molecular structure and polarity, KI and ethanol are soluble, while Cl₂ is not.
