A chemical reaction `A + 2B rArr AB_(2)` follows in two steps
`A + B rArr` AB(slow)
`AB + B rArr AB_(2)` (fast)
Then the order of the reaction is

Options

A. 3
B. 2
C. 1
D. 0

Explanation

To determine the order of the reaction given the two-step mechanism:

1. **Identify the slow step**: The slow step in the reaction mechanism is the first step:
\[ A + B \rightarrow AB \quad (\text{slow}) \]
This step is crucial because it is the rate-determining step.

2. **Write the rate law for the slow step**: The rate of a reaction is expressed in terms of the concentrations of the reactants involved in the rate-determining step. For the slow step, the rate law can be written as:
\[ \text{Rate} = k[A]^1[B]^1 \]
where \(k\) is the rate constant.

3. **Determine the order of the reaction**: The order of the reaction is determined by the sum of the exponents in the rate law. In this case, we have:
- The exponent for \([A]\) is 1.
- The exponent for \([B]\) is also 1.

Therefore, the total order of the reaction is:
\[ \text{Order} = 1 + 1 = 2 \]

4. **Conclusion**: The overall order of the reaction \(A + 2B \rightarrow AB_2\) is 2.