Step-by-step explanation:
It is given that volume is 7.68 L, temperature is 355 k and pressure is 8.57 atm. So, according to ideal gas equation PV = nRT.
Also, it is known that number of moles equal mass divided by molar mass.
Therefore, putting the given values into the ideal gas equation as follows.
PV = nRT
=
![n * 0.082 atm L/mol K * 355 K](https://img.qammunity.org/2019/formulas/chemistry/middle-school/dea8pfh0ov19vae1f4i4rtolwhf9c79qnt.png)
n = 2.26 mol
Thus, we can conclude that the number of moles present in given oxygen is 2.26 mol.