The rate of reaction `A + B rarr` Product is given by the equation `r = k[A][B]`. If `B` is taken in large excess, the order of the reaction would be

Options

A. `a. 2`
B. `b. 1`
C. `c. 0`
D. d. Unpredictable

Explanation

To determine the order of the reaction when reactant B is in large excess, we can follow these steps:

### Step 1: Understand the Rate Law
The rate of the reaction is given by the equation:
\[ r = k[A][B] \]
where \( r \) is the rate of the reaction, \( k \) is the rate constant, and \([A]\) and \([B]\) are the concentrations of reactants A and B, respectively.

### Step 2: Analyze the Excess Reactant
Since reactant B is taken in large excess, its concentration will not change significantly during the reaction. This means that \([B]\) can be considered constant.

### Step 3: Modify the Rate Law
When \([B]\) is constant, we can redefine the rate equation. We can express the rate as:
\[ r = k[A][B] = (k[B]) [A] \]
Let’s denote \( k' = k[B] \), where \( k' \) is a new constant that combines the original rate constant \( k \) and the constant concentration of B.

### Step 4: Simplify the Rate Expression
Now, the rate expression simplifies to:
\[ r = k'[A] \]
This shows that the rate of the reaction depends only on the concentration of A.

### Step 5: Determine the Order of the Reaction
The order of the reaction is determined by the power to which the concentration of the reactants is raised in the rate law. In this case, since the rate depends only on \([A]\) and is raised to the first power, the order of the reaction with respect to A is 1.

### Conclusion
Thus, when B is in large excess, the order of the reaction is 1.

### Final Answer
The order of the reaction is 1.

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