chemistry
posted by Anonymous .
A gaseous mixture of O2 and N2 contains 34.8% nitrogen by mass. What is the partial pressure of oxygen in the mixture if the total pressure is 465 mmHg?

0.348 x 465 mm = partial pressure N2.
partial pressure O2 = 465  partial pressure N2 OR
partial pressure oxygen = 465 x (1.00  0.348) = 
This is incorrect, It says "by mass" not "by moles". therefore you must find the number of moles and use the mole fraction

First you find the moles of N2 assuming that you have 34.8 grams of N2. Then you find the moles of O2 assuming that you have 65.2 grams of O2.(100%34.8%=65.2% so there is 65.2g O2). The partial pressure equals mole fraction x the total pressure(mole fraction= moles of O2/total moles in mixture) so in the end you multiply 465mmHg x mole fraction and theres your answer. :)