For the reaction :
` A +H_2 O to B` rate ` prop [A]` what is its
molecularity

Explanation

To determine the molecularity of the reaction \( A + H_2O \to B \) where the rate is proportional to the concentration of \( A \), we can follow these steps:

### Step 1: Understand the Reaction
The reaction involves the reactants \( A \) and \( H_2O \) (water) combining to form the product \( B \).

### Step 2: Identify the Rate Law
The problem states that the rate of the reaction is proportional to the concentration of \( A \). This can be expressed as:
\[
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