Need assistance with this osmotic pressure problem?

Question

I know how to use the formula for osmotic pressure, however the way that this problem incorporates partial pressure into it just confuses the sh*t outta me. Please help me, before I cut my wrists.


The partial pressure of O2 in air at sea level is 0.21 atm. The solubility of O2 in water is 1.38 x 10-3 M at 20°C and Poxygen = 1.00 atm. Calculate the molar concentration of O2 in the surface water of a mountain lake saturated with air at 20°C and an atmospheric pressure of 662.8 torr.

Answer 1

You need no osmotic pressure but henry law

c=kp here the number of mole of O2 dissolved is c p is the pressure k is expreesed for a voume of 1L

so here c =1.38 10^-3 * 0.21 * 662.8/760= 2.53 10^-4mole/L

I explain 1.38 10^-3 is for 1 atm =760 torrs so here you have only 662.8 torr hence the ratio 662.8/760 and the number 0.21 since O2 IS ONLY 0.21

Answer 2

8.55 = CRT = C x 0.08206 x 280 C = 0.372 = moles sucrose / 0.548 moles sucrose = 0.204 multiply by the molar mass