**Assertion (A):** Vapor density of a gas is half of its molecular weight. <br>**Reason (R):** Vapor — Mole Concept and Some Basic Concepts of Chemistry Chemistry Question

💡 Solution & Explanation

By definition, $VD = \frac{\text{Mass of } V \text{ L gas}}{\text{Mass of } V \text{ L } H_2} = \frac{MW_{gas}}{MW_{H_2}} = \frac{MW}{2}$. The reason provides the physical basis for the formula $MW = 2 \times VD$. [1, 13]