Decomposition of `Hl (g)` on Gold surface is zero order reaction. Initially, few moles of `H_(2)` are present in container then which of the following graph is correct ?

Options

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B.
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D.

Answer

To determine the correct graph for the decomposition of HI (g) on a gold surface, which is a zero-order reaction, we need to analyze the characteristics of zero-order reactions and the initial conditions given in the problem.

### Step-by-Step Solution:

1. **Understanding Zero-Order Reactions**:
- In a zero-order reaction, the rate of reaction is constant and does not depend on the concentration of the reactants. The rate law for a zero-order reaction can be expressed as:
\[ \text{Rate} = k \]
- The integrated rate law for a zero-order reaction is:
\[ [A] = [A_0] - kt \]
where \([A]\) is the concentration of the reactant at time \(t\), \([A_0]\) is the initial concentration, and \(k\) is the rate constant.

2. **Initial Conditions**:
- The problem states that initially, few moles of \(H_2\) are present in the container. This means that the concentration of \(H_2\) is not zero at the start of the reaction.

3. **Graph Characteristics**:
- For a zero-order reaction, if we plot the concentration of the reactant (or product) versus time, the graph will be a straight line with a negative slope, starting from the initial concentration.
- Since \(H_2\) is already present, the graph will start from a positive value (the initial concentration of \(H_2\)) and will decrease linearly over time.

4. **Identifying the Correct Graph**:
- The graph should show a straight line that starts above the origin (due to the initial concentration of \(H_2\)) and slopes downward as time progresses.
- The correct graph will not pass through the origin but will be parallel to the time axis, starting from the initial concentration of \(H_2\) and decreasing linearly.

5. **Conclusion**:
- Based on the characteristics of zero-order reactions and the initial conditions, the correct graph is the one that starts from a positive concentration value and decreases linearly over time.

### Final Answer:
The correct graph is the one that starts from the initial concentration of \(H_2\) and decreases linearly over time.