See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Solution: Why Cyclohexane Floats on Water **Step 1: Identify the fundamental principle** An object floats on a liquid when its density is less than the liquid's density. This is the basic criterion for buoyancy (Archimedes' principle). **Step 2: Compare densities** - Density of cyclohexane: $\approx 0.78 \text{ g/cm}^3$ - Density of water: $1.00 \text{ g/cm}^3$ Since $\rho_{\text{cyclohexane}} < \rho_{\text{water}}$, cyclohexane will float. **Step 3: Evaluate other options** - **(A) & (B) & (C):** These refer to conformational isomers of cyclohexane (boat, chair, crown forms). While cyclohexane does adopt the **chair conformation** in reality, the *reason* for floating is not its molecular shape—it's the density difference. - **Chair vs. boat** conformations affect stability and steric strain, not flotation behavior. **Step 4: Why (D) is correct** The direct cause of floating is that cyclohexane is **less dense than water**. This density difference allows the buoyant force to exceed the weight of the cyclohexane, causing it to float regardless of its molecular conformation. **Answer: (D)** — Cyclohexane floats because it is less dense than water. This is the fundamental thermodynamic reason, independent of molecular structure.