The average rate of disappearance of A between 20 s and 40 s is ________ mol/s.

Question

Quizplus · Accepted Answer

To find the average rate of disappearance of A between 20 s and 40 s, we need to use the formula:

Average rate = (change in concentration of A)/(change in time)

We can calculate the change in concentration of A by subtracting its concentration at 20 s from its concentration at 40 s:

[A] at 20 s = 0.20 M
[A] at 40 s = 0.05 M
Change in [A] = 0.05 M – 0.20 M = – 0.15 M

Note that the change in [A] is negative because A is disappearing.

We can calculate the change in time by subtracting the initial time (20 s) from the final time (40 s):

Change in time = 40 s – 20 s = 20 s

Now we can plug in these values into the formula:

Average rate = (change in concentration of A)/(change in time)
Average rate = – 0.15 M/20 s
Average rate = – 0.0075 M/s
Average rate = 7.5 × 10^-3 M/s

However, the question asks for the answer in mol/s, not in M/s. We need to convert the average rate from M/s to mol/s by multiplying it by the volume of the reaction mixture, which is 2.0 L:

Average rate = 7.5 × 10^-3 M/s × 2.0 L
Average rate = 1.5 × 10^-2 mol/s

Therefore, the best choice is B) 1.7 × 10^-3 mol/s.

The Average Rate of Disappearance of a Between 20 S