`alpha-"sulphur" Leftrightarrow beta-` sulphur is an example to

Options

A. Physical equilibrium
B. chemical equilibrium
C. Irreversible reaction
D. Both physical and chemical equilibrium

Answer

To determine the type of equilibrium represented by the reaction between alpha-sulfur and beta-sulfur, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reaction**: The reaction given is alpha-sulfur ↔ beta-sulfur. This indicates that alpha-sulfur can transform into beta-sulfur and vice versa.

2. **Understand Physical Equilibrium**: Physical equilibrium occurs when a substance changes its state or phase, such as solid to liquid or liquid to gas, without altering its chemical composition. In this case, alpha-sulfur and beta-sulfur are different forms (allotropes) of sulfur, but they are still sulfur.

3. **Understand Chemical Equilibrium**: Chemical equilibrium is established when a chemical reaction occurs, and the rate of the forward reaction equals the rate of the reverse reaction. This typically involves a change in the chemical identity of the substances involved.

4. **Understand Irreversible Reactions**: An irreversible reaction is one that proceeds in only one direction, where reactants are converted into products without the possibility of reverting back to the original reactants.

5. **Analyze the Given Reaction**: In the case of alpha-sulfur and beta-sulfur, the reaction involves a change in the physical state or allotrope of sulfur, but does not involve a change in its chemical identity. Therefore, it is not a chemical reaction in the traditional sense.

6. **Conclusion**: Since the reaction involves a change in the form of sulfur without changing its chemical composition, it is an example of physical equilibrium.

### Final Answer:
The reaction alpha-sulfur ↔ beta-sulfur is an example of **physical equilibrium**.