Question

In the reaction, A → Products, the rate constant is 3.6 × 10−4 s−1. If the initial concentration of A is 0.548 M, what will be the concentration of A (in M) at t = 99.2 s? Only enter the numerical value with three significant figures in the answer box below. Do NOT type in the unit (M).

Answer 1

Answer:

        $\large\boxed{\large\boxed{0.529M}}$

Explanation:

Since the rate constant has units of s⁻¹, you can tell that the order of the reaction is 1.

Hence, the rate law is:

       $r=d[A]/dt=-k[A]$

Solving that differential equation yields to the well known equation for the rates of a first order chemical reaction:

      $[A]=[A]_0e^{-kt}$

You know [A]₀, k, and t, thus you can calculate [A].

       $[A]=0.548M\times e^{-3.6\cdot 10^{-4}/s\times99.2s}$

       $[A]=0.529M$