In the first order reaction A --> products, where beginning A concentration C0 0.1 0.5 1 1.5 2 5 mol/dm3, with given k value as 0.1 0.2 0.5 1 2 1/s, calculate the molar concentration of substrate A for every second of reaction for 5 10 15 20 30 40 50 60 .

To calculate the progress of reaction, and, the concentration change, we will use the following formula:

where k - first order rate constant[1/s], t -time [s], C0 - starting concentration[mol/dm3]

Then, for every second ( starting from 0) as t value, and for k putting 1/s, we can calculate the concentration value over time.

Take few k-values from the list and observe, that the higher k-value is, the faster our A concentration drops, means - the faster process goes from A ---> products.

Time	[unit]	[A]	[unit]
0	s	0	mol/dm3

As you probably noticed, the change of concentration between selected two seconds is lower comparing to previous two secods period. It is because the the concentration of our A substrate drops, so the driving force as well. Due to that the change of concentration in time is not linear

Having k constant we can also calculate a half-life, which is a period, in which the concentration drops by half

The formula is a following:

So, in our case, when k = [1/s], the half-life will equal INF s

And indeed, when you see the concentration at e.g. the beginning, and then after the half-life time ( in seconds) you will see that the value two times lower. It works also for any other INF s period