Under Dalton's law, we can use the mole fraction of a gas to find the partial pressure of that gas here, we're gonna say, Dalton's law says that the partial pressure of a gas one equals the mole fraction of that gas, one times the total pressure. So if you don't quite remember how to calculate mole Fraction, I suggest you go back and take a look at my topic videos on mole fractions before proceeding further under Dalton's law.