chapter 7.  ELEMENTS OF GROUPS 16, 17 AND 18 class 12 chemistry textbook solution

Answer:-

Rhombic sulfur and monoclinic sulfur are two different allotropes of sulfur, meaning they have the same chemical element but different structural arrangements of sulfur atoms in the solid state. Here are the key distinctions between them:

1. Crystal Structure:

   • Rhombic Sulfur: Rhombic sulfur, also known as α-sulfur, has a crystal structure in which sulfur atoms are arranged in a puckered, puckered or crown-shaped ring structure. This structure consists of S8 rings, where eight sulfur atoms form a ring, and these rings are loosely packed in the crystal lattice.
   • Monoclinic Sulfur: Monoclinic sulfur, also known as β-sulfur, has a crystal structure in which sulfur atoms are arranged in a layered structure. The layers consist of puckered S8 rings similar to those in rhombic sulfur, but the layers are more tightly packed and arranged in a monoclinic crystal lattice.

2. Physical Appearance:

   • Rhombic Sulfur: Rhombic sulfur appears as yellow, translucent crystals or a fine powder. It has a powdery or crystalline texture and is relatively stable at room temperature.
   • Monoclinic Sulfur: Monoclinic sulfur appears as dark red-brown crystals. It tends to have a more amorphous or glassy appearance compared to rhombic sulfur.

3. Stability:

   • Rhombic Sulfur: Rhombic sulfur is the stable form of sulfur at temperatures below 95.5°C. It can exist in a stable state at room temperature and is the most common form of sulfur encountered under standard conditions.
   • Monoclinic Sulfur: Monoclinic sulfur is the stable form of sulfur at temperatures above 95.5°C and below 119°C. It undergoes a phase transition from rhombic to monoclinic sulfur at 95.5°C.

4. Transition Temperature:

   • The transition temperature between rhombic and monoclinic sulfur is 95.5°C. Below this temperature, rhombic sulfur is stable, and above this temperature, monoclinic sulfur is stable.

5. Chemical Properties:

   • Both rhombic and monoclinic sulfur have similar chemical properties because they are both composed of sulfur atoms (S8 molecules). They can undergo reactions such as combustion to form sulfur dioxide (SO2) when exposed to oxygen.

In summary, the primary differences between rhombic sulfur and monoclinic sulfur lie in their crystal structures, physical appearances, stability at different temperatures, and the transition temperature between them. Rhombic sulfur is the stable form at lower temperatures, while monoclinic sulfur is stable at higher temperatures.