To calculate the concentration remaining after a certain time, we can use the equation
. Using the given information, we can substitute the values and solve for the concentration remaining after 20.0 min.
To calculate the concentration remaining after a certain time, we can use the equation:

Where C is the concentration at the specified time, C₀ is the initial concentration, k is the rate constant, and t is the time.
Using the given information, we have:
C₀ = 0.0200 M

t = 20.0 min = 20.0 min * (1 min / 60 s) = 0.333 hours
Substituting these values into the equation, we can calculate the concentration remaining after 20.0 min:

Solving this equation will give us the final concentration.