1. Identify the number of oxygen atoms per molecule:

* The formula CH3CO2H represents acetic acid.

* There are two oxygen atoms in each molecule of acetic acid (O2).

2. Calculate the total number of oxygen atoms:

* Multiply the number of oxygen atoms per molecule by the total number of molecules: 2 oxygen atoms/molecule * 300 molecules = 600 oxygen atoms

Therefore, there are 600 oxygen atoms in 300 molecules of CH3CO2H (acetic acid).