The Henry's law constant (kH) for O2 in water at 20 C is 1.28x10^-3 mol/(L*atm).?

http://chemwiki.ucdavis.edu/Physical_Chemistry/Phy...

The basic equation is

C = kH * Pgas

where

C = the solubility of the gas at a fixed temperature in a particular solvent

kH = Henry's law constant

Pgas = the partial pressure of the gas

However, there are alternative forms of the equation.

http://www.henrys-law.org/

So for your problem, let's have a look:

kH = 1.28 x 10^-3 mol L^-1 atm^-1

When this is multiplied by pressure, we get the units mol/L, which is concentration. Therefore, the original form of the equation can be used.

I'll set the first one up and let you complete it.

"(a) How many grams of O2 will dissolve in 1.75 L of H2O that is in contact with pure O2 at 1 atm? "

First calculate the oxygen concentration:

C = kH * Pgas

C = (1.28 x 10^-3 mo L^-1 atm^-1)*(1 atm)

C = ____ mol/L

Next, multiply the concentration by the volume to calculate the moles of oxygen present in the specified volume:

moles oxygen = (concentration of oxygen)*(volume)

moles oxygen = ( ____ mol/L)*(1.75 L) = ____ moles oxygen

Then calculate the moles of oxygen by the molar mass of oxygen to calculate the mass of oxygen in the specified volume:

mass of oxygen = (moles of oxygen)*(molar mass of oxygen)

mass of oxygen = ( ____ moles of oxygen*(31.9998 g.mol) = ____ g of oxygen

(molar mass calculated from atomic weight of O here: http://www.webelements.com/)

See if you can use that as a guide to do (b) on your own.