What pressure in kPa will be exerted by 4.78 grams of oxygen gas in a 2.5 liter container at 20 degrees celsius? just confused on what to put in for n in PV=nRT

Use number of mole=mass (in grams) divided by molar mass

AKA n=m/Mr

->Using the mass (4.78g) given to you until he question. Then put the number of mole in pV=nRT but rearrange to

p=nRT divided by volume (V).

AKA p=nRT/V

Also don't forget to convert your temperature to Kelvins (add 273 to your temperature)