When hydrogen molecules decompose into its atoms, which conditions give the maximum yield of hydrogen atoms ?

Options

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

Answer

To determine the conditions that give the maximum yield of hydrogen atoms when hydrogen molecules decompose into their atomic form, we need to analyze the reaction and apply Le Chatelier's principle.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
The decomposition of hydrogen molecules (H₂) into hydrogen atoms (H) can be represented by the following reaction:
\[ \text{H}_2(g) \rightleftharpoons 2\text{H}(g) \]
This reaction involves the conversion of 1 mole of hydrogen gas into 2 moles of hydrogen atoms.

2. **Identifying the Nature of the Reaction**:
The decomposition of hydrogen molecules into atoms is an endothermic process. This means that it requires heat to proceed. Therefore, heat is a reactant in this reaction.

3. **Applying Le Chatelier's Principle**:
According to Le Chatelier's principle, if a system at equilibrium is subjected to a change in temperature, pressure, or concentration, the system will adjust itself to counteract that change.

4. **Effect of Temperature**:
- Since the reaction is endothermic, increasing the temperature will favor the forward reaction (decomposition of H₂ into H). This is because the system will try to absorb the added heat.
- Therefore, **higher temperatures** will lead to a greater yield of hydrogen atoms.

5. **Effect of Pressure**:
- The reaction involves a change in the number of moles of gas. On the left side, there is 1 mole of H₂, and on the right side, there are 2 moles of H.
- According to Le Chatelier's principle, increasing the pressure will favor the side with fewer moles of gas. In this case, that is the reactant side (H₂).
- Therefore, to maximize the yield of hydrogen atoms, **lower pressure** is favorable.

6. **Conclusion**:
To achieve the maximum yield of hydrogen atoms from the decomposition of hydrogen molecules, the optimal conditions are:
- **High temperature**
- **Low pressure**

### Final Answer:
The conditions that give the maximum yield of hydrogen atoms are **high temperature and low pressure**.

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