Naphthalene is a volatile solid. It is best purified by :

Options

A. crystallisation
B. distillation
C. steam distillation
D. sublimation

Answer

To determine the best method for purifying naphthalene, a volatile solid, we can follow these steps:

### Step 1: Understand the Properties of Naphthalene
Naphthalene is a solid at room temperature but has a relatively low boiling point. It can easily be converted into vapor when heated.

**Hint:** Consider the physical state and boiling point of the substance when thinking about purification methods.

### Step 2: Identify the Purification Methods
Common methods for purifying solids include recrystallization, distillation, and sublimation. Each method has its own applicability based on the properties of the substance being purified.

**Hint:** Recall the characteristics of each purification method and their suitability for different types of compounds.

### Step 3: Analyze Sublimation
Sublimation is the process where a solid converts directly into vapor without passing through the liquid phase. Since naphthalene is a volatile solid, sublimation is a suitable method for its purification.

**Hint:** Think about how sublimation can separate a solid from impurities that do not sublime.

### Step 4: Conclude the Best Method
Given that naphthalene can be easily converted into vapor, the best method for purifying it is sublimation. This process will allow naphthalene to be separated from non-volatile impurities effectively.

**Hint:** Consider the efficiency of sublimation in removing impurities while retaining the desired compound.

### Final Answer
Naphthalene is best purified by sublimation.