Consider the given reactions:
[a] `H_2+Cl_2 to^(sun light) 2HCL`
[b] `H_2+Br_2 to 2HBr [c] H_2+I_2 to 2HI`
The order of reaction a,b,c respectively is:

Options

A. 2,1,0
B. `0,3/2,2`
C. `1,2,2`
D. 2,1,1

Answer

To determine the order of the reactions given in the question, we will analyze each reaction step by step.

### Step 1: Analyze Reaction [a]
**Reaction:** \( H_2 + Cl_2 \xrightarrow{sunlight} 2HCl \)

- This reaction occurs in the presence of sunlight, indicating that it is a photochemical reaction.
- The order of a photochemical reaction is generally considered to be zero because the rate of reaction does not depend on the concentration of the reactants.

**Order of Reaction [a]:** 0

### Step 2: Analyze Reaction [b]
**Reaction:** \( H_2 + Br_2 \rightarrow 2HBr \)

- This reaction is not a photochemical reaction and requires experimental determination to find its order.
- The rate expression can be derived from experimental data. It is typically found that:
\[ r = k[H_2]^1[Br_2]^{1/2} \]
- Here, the order with respect to \( H_2 \) is 1 and with respect to \( Br_2 \) is \( \frac{1}{2} \).
- To find the overall order, we sum the powers:
\[ \text{Order} = 1 + \frac{1}{2} = \frac{3}{2} \]

**Order of Reaction [b]:** \( \frac{3}{2} \)

### Step 3: Analyze Reaction [c]
**Reaction:** \( H_2 + I_2 \rightarrow 2HI \)

- This reaction can also be analyzed similarly to reaction [b].
- The rate expression can be derived as:
\[ r = k[H_2]^1[I_2]^1 \]
- Both \( H_2 \) and \( I_2 \) have an order of 1.
- Thus, the overall order is:
\[ \text{Order} = 1 + 1 = 2 \]

**Order of Reaction [c]:** 2

### Final Summary of Orders
- Order of Reaction [a]: 0
- Order of Reaction [b]: \( \frac{3}{2} \)
- Order of Reaction [c]: 2

### Conclusion
The order of reactions a, b, and c respectively is:
**0, \( \frac{3}{2} \), 2**