Under what conditions of temperature and pressure the formation of atomic hydrogen from molecular hydrogen will be favoured most ?

Options

A. High temperature and high pressure
B. Low temperature and low pressure
C. High temperature and low pressure
D. Low temperature and high pressure

Answer

To determine the conditions of temperature and pressure under which the formation of atomic hydrogen from molecular hydrogen is favored, we can analyze the reaction using Le Chatelier's principle.

### Step-by-Step Solution:

1. **Understand the Reaction**:
The formation of atomic hydrogen (H) from molecular hydrogen (H₂) can be represented as:
\[ H_2 \rightleftharpoons 2H \]
This reaction indicates that one molecule of hydrogen gas dissociates into two hydrogen atoms.

2. **Identify the Nature of the Reaction**:
- The reaction is endothermic, meaning it requires energy (heat) to proceed. This is because breaking the H-H bond in molecular hydrogen requires energy input.

3. **Effect of Temperature**:
- According to Le Chatelier's principle, if we increase the temperature of an endothermic reaction, the equilibrium will shift in the direction that absorbs heat (the forward direction in this case).
- Therefore, to favor the formation of atomic hydrogen, we need to **increase the temperature**.

4. **Effect of Pressure**:
- The reaction involves a change in the number of moles of gas. On the left side, we have 1 mole of H₂, and on the right side, we have 2 moles of H.
- According to Le Chatelier's principle, increasing the pressure will favor the side with fewer moles of gas. Since the left side has 1 mole and the right side has 2 moles, increasing the pressure will shift the equilibrium to the left, favoring the formation of H₂.
- To favor the formation of atomic hydrogen, we need to **decrease the pressure**.

5. **Conclusion**:
- The optimal conditions for the formation of atomic hydrogen from molecular hydrogen are **high temperature** and **low pressure**.

### Final Answer:
The formation of atomic hydrogen from molecular hydrogen is favored under conditions of **high temperature and low pressure**.