Final answer:
To calculate the time required for the concentration of XY to decrease from 0.160 M to 6.40×10−2 M, the rate constant of the first-order reaction is required. Without this or additional details about the reaction, the exact time cannot be determined.
Step-by-step explanation:
To determine how long it will take for the concentration of substance XY to decrease from an initial concentration of 0.160 M to 6.40×10−2 M, we need to know the order of the reaction and the rate constant (k). Assuming it follows a first-order reaction, the relationship between time (t), the initial concentration ([A]0), and the final concentration ([A]) can be described by the following equation derived from the integrated rate law for a first-order reaction:
ln([A]0/[A]) = kt
If we have the rate constant (k), we can solve for time (t) using the given concentrations. However, without the rate constant or additional information about the reaction mechanism, it's not possible to calculate the exact time required. Additional information such as the reaction temperature and the presence of any catalysts would also be relevant in an actual scenario.