# What is an example of a rate of reactions practice problem?

##### 1 Answer

Here's an example of a rate of reaction problem:

*What is the rate constant k for the* **first-order** *decomposition of* *at* *if the half-life of* *at that temperature is* *seconds? Under these conditions, what percentage of* *molecules will not have reacted after 1 day?*

We know that half-life represents the time needed for a reactant's concentration to reach half of its initial value. The equation for the half-life of a reactant in a **first-order** reaction is given by

Since we know that

Since this is a first-order reaction, the equation we'll use to determine what percentage is left unreacted is

Since

Converting **1 day** to **seconds** will give

This means that

Therefore, the percentage left unreacted is