Answer:
is the correct answer to the given question.
Explanation:
Given k=6.40 x 10-3 min-1.
According to the first order reaction .
The concentration of time can be written as
![[\ A\ ]\ = \ [\ A_{0}\ ] * e \ ^\ {-kt}](https://tex.z-dn.net/?f=%5B%5C%20A%5C%20%5D%5C%20%3D%20%5C%20%5B%5C%20%20A_%7B0%7D%5C%20%5D%20%20%2A%20e%20%5C%20%5E%5C%20%20%7B-kt%7D)
Here
= Initial concentration.
So ![[\ A\ ]_{0}= 0.0314 M](https://tex.z-dn.net/?f=%5B%5C%20A%5C%20%5D_%7B0%7D%3D%200.0314%20M)
Putting this value into the above equation.

=0.211 M
This can be written as

Both elements and compounds are pure substances. While elements are not made of simpler substances, compounds are made up of two or more chemical elements that are chemically combined.