AP Chemistry help? Number of molecules and partial pressure?

First you need to figure out how much oxygen is in 1.05L. 0.21* 1.05 = .2205 L of oxygen. There is 16 g in 1 mole of oxygen. Molarity is moles / liter. So 16 / .2205 =72.56moles x 6.023E23 =4.369E25

PV=nRT, where P= pressure in atmospheres (760 torr=1atm), V = volume in Liters, n= number of moles, R= gas constant .0821, and T= temperature in K (C + 273)

Plugging in the numbers:
(740/760 atm)(1.05)=n(.0821)(37 + 273)
n= .0402 moles.

1 mole = 6.02 x 10^23
(.0402)( 6.02 x 10^23) = 2.42 x 10^22 molecules of air.

Molecules of Oxygen is 21 % of that amount.
(2.42 x 10^22) (0.21) = 5.08 x 10^21 molecues O2

For partial pressure, use PV = nRT, using the moles of air you just solved for, and solve for P first.
PV= nRT
P(1.05)=(.0402)(.0821)(310)
P= .9744 atm

oxygen is 21% of this pressure:
.9744 x .21= .2046 atm O2

Subtract the pressure of Oxygen from the whole , or find 79% of the whole to find the partial pressure of Nitrogen:
.9744 - .2046= .7698 atm N2