The decomposition of HI into `H_2` AND` I_2` is an example of

Options

A. first order reaction
B. second order reaction
C. zero order reaction
D. pseudo first order reaction

Answer

To determine the type of reaction for the decomposition of HI into H2 and I2, we can follow these steps:

### Step 1: Write the balanced chemical equation
The decomposition of hydrogen iodide (HI) can be represented by the balanced equation:
\[ 2 \, \text{HI} \, \rightarrow \, \text{H}_2 \, + \, \text{I}_2 \]

### Step 2: Identify the order of the reaction
To classify the reaction, we need to determine its order. The order of a reaction is defined based on the rate law, which is derived from experimental data.

### Step 3: Write the rate law expression
For the given reaction, the rate law can be expressed as:
\[ \text{Rate} = k [\text{HI}]^n \]
where \( k \) is the rate constant and \( n \) is the order of the reaction.

### Step 4: Determine the order from experimental data
In this case, it has been experimentally determined that the rate of the reaction is proportional to the square of the concentration of HI:
\[ \text{Rate} \propto [\text{HI}]^2 \]
This indicates that the reaction is second order with respect to HI.

### Step 5: Conclusion
Since the reaction follows a rate law where the exponent of the concentration of the reactant (HI) is 2, we conclude that the decomposition of HI into H2 and I2 is an example of a **second-order reaction**.