Question

What is the molar concentration (mmol/mL) of oxygen in ultrafiltrate/plasma consisting only of air? And of pure oxygen?

Assume: ultrafiltrate=plasma=water, only worry about oxygen solubilty, the aqueous oxygen solubilty is variable with temperature, total gas pressure over the aquesous phase is 1 ATM, in equilibrium.

I'm trying to use Henry's Law to solve this.

Answer 1

The oxygen will form an equilbrium between dissolved oxygen and undissolved oxygen in plasma.

O2(aq( --> O2(g)

K = pO2 / [O2]

And this is known as henry's law that the concentration of dissolved gas in water is directly proportional of partial pressure of gas.

Now the concentration of oxygen in air is 20.94 moles %

at 1 atm pressure the partial pressure of oxygen = 0.209 atm

Now Henry's constant of oxygen in water at 298 K is 756.7 atm mol^-1L-1

so moalr concentration = pO2 / K = 0.209 / 756.7 = 2.761 X 10^-4 moles / L

or 0.2761 millimoles / L