Question

A gaseous mixture of O2 and N2 contains 32.8% nitrogen by mass

How do i figure out wat the mass is?

Answer 1

Mass of what? I don't think there is enough information to determine the mass of either oxygen or nitrogen. You know, of course, that percent oxygen = 100-32.8.

Answer 2

oh sry, didn't the whole question

A gaseous mixture of O2 and N2 contains 32.8% nitrogen by mass. What is the partial pressure of oxygen in the mixture if the total pressure is 665mmHg ?

would i start by calculating the number of moles of nitrogen? if so how?

Answer 3

Have you had anything about mole fractions? There may be a short way of solving this problem but I would suggest the following, although it is long.
I would assume a mass of total gas of some number. Then 67.2% of that number and 32.8% of that number will give you grams of N2 and grams O2. Then convert each to mols, determine mole fraction from that, then partial pressure = mole fraction x 665 to give pressure of each.