Exponential Decay

[Baza AlAbdullah 2F]

Hello!

What does exponential decay on a graph tell us about a first order reaction?

Thank you!

[Aarushi Anil 1C]

If you were to plot concentration [A] vs time instead of ln[A] vs time for a first order reaction, the graph would exponentially decay.

[JeffreyL]

Just to clarify and expand on the other reply, if you see exponential decay in a graph whether it be [A] vs time, ln[A] vs time, or 1/[A] vs time, it means that the y-axis chosen to represent that graph and the order that corresponds to the y-axis are not a fit for the data. For all of the graphs I mentioned, the data must produce a linear graph in order to be first order, second order, or zero order depending on which corresponding graph you're looking at. Therefore, if you see exponential decay, this means the corresponding order of the graph you're looking at is NOT the order of the reaction.

[Denise Mora 1C]

Let's take the reaction X-> Y, as an example. A first-order reaction changes its rate with the concentration of reactants: rate=k[X]. Since X is being used up in the reaction, the rate will continuously decrease because the amount of X that decomposes during the first minute is different than the amount of X that decomposes during the second minute, resulting in an exponential decay graph.

[106062642]

The concentration of just one reactant determines the reaction's rate in a first-order reaction. This indicates that the concentration of that reactant decreases exponentially over the course of the reaction.