For the reaction, `H_(2(g)) + Br_(2(g)) to 2HBr_((g))`, the reaction rate `= k [H_(2)][Br_(2)]^(1//2)`. Which statement is true about this reaction?

Options

A. The reaction is of second order
B. Molecularity of the reaction is 3/2
C. The unit of k is `sec^(-1)`
D. Molecularity of the reaction is 2.

Answer

To analyze the reaction \( H_2(g) + Br_2(g) \rightarrow 2HBr(g) \) and determine the correct statement about it based on the given rate law \( \text{Rate} = k [H_2][Br_2]^{1/2} \), we can follow these steps:

### Step 1: Identify the Molecularity of the Reaction
Molecularity refers to the number of reactant molecules involved in an elementary reaction. In this case, we have:
- 1 molecule of \( H_2 \)
- 1 molecule of \( Br_2 \)

Thus, the total molecularity is:
\[ \text{Molecularity} = 1 + 1 = 2 \]

### Step 2: Determine the Order of the Reaction
The order of a reaction is determined by the sum of the exponents in the rate law. From the given rate law:
\[ \text{Rate} = k [H_2]^1 [Br_2]^{1/2} \]
We can see that:
- The order with respect to \( H_2 \) is 1.
- The order with respect to \( Br_2 \) is \( \frac{1}{2} \).

Therefore, the overall order of the reaction is:
\[ \text{Overall Order} = 1 + \frac{1}{2} = \frac{3}{2} \]

### Step 3: Conclusion
Based on the analysis:
- The molecularity of the reaction is 2.
- The order of the reaction is \( \frac{3}{2} \).

Thus, the true statement about this reaction is that the molecularity is 2.

### Final Answer
The correct statement is: **The molecularity of the reaction is 2.**

---