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]
The reaction is:
\[ H_2 + Cl_2 \xrightarrow{sunlight} 2HCl \]

This is a photochemical reaction, which means it occurs in the presence of light. Photochemical reactions typically have an order of 0. This is because the rate of the reaction does not depend on the concentration of the reactants; instead, it is controlled by the intensity of light.

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

### Step 2: Analyze Reaction [b]
The reaction is:
\[ H_2 + Br_2 \rightarrow 2HBr \]

For this reaction, we can derive the order experimentally. The rate law for this reaction can be expressed as:
\[ \text{Rate} = k [H_2]^m [Br_2]^n \]

Through experimentation, it has been found that:
- The order with respect to \( H_2 \) is \( \frac{1}{2} \) (m = 1/2).
- The order with respect to \( Br_2 \) is \( 1 \) (n = 1).

Thus, the total order of the reaction is:
\[ \text{Total Order} = m + n = \frac{1}{2} + 1 = \frac{3}{2} \]

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

### Step 3: Analyze Reaction [c]
The reaction is:
\[ H_2 + I_2 \rightarrow 2HI \]

Similar to reaction [b], we can derive the order experimentally. The rate law can be expressed as:
\[ \text{Rate} = k [H_2]^p [I_2]^q \]

Through experimentation, it has been determined that:
- The order with respect to \( H_2 \) is \( 1 \) (p = 1).
- The order with respect to \( I_2 \) is also \( 1 \) (q = 1).

Thus, the total order of the reaction is:
\[ \text{Total Order} = p + q = 1 + 1 = 2 \]

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

### Final Summary
Now we can summarize the orders of the reactions:
- Order of Reaction [a]: 0
- Order of Reaction [b]: \( \frac{3}{2} \)
- Order of Reaction [c]: 2

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

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