Solubility of O2.....

Henry's law relates the partial pressure of the gas to the concentration of the gas. The ratio is equal to an empirically determined constant which is unique for each gas. The Henry's law constant you have given and (checked at https://chemengineering.wikispaces.com/Henry%27s+L... ) has units of mole/Latm. Therefore, the pressure in torr must be converted to atm (1 atm = 760 torr, exact). It is very important to include the proper units with every number.

140. torr x (1 atm / 760 torr) = 0.184 atm

c = k(H) p ......where c = concentration of the gas, k(H) = Henry's law constant, p = partial pressure

c = 1.3x10^-3 mol/Latm x 0.184 atm = 2.39x10^-4 mol/L ......... this is the molar solubility

Solubility of O2 = 2.39x10^-4 mol / 1L x (32.0g O2 / 1 mol O2) x (0.1L / 100 mL) = 7.65x10^-4 g O2 / 100 mL water

Note: This is the solubility when the partial pressure is 0.184 atm, not 1 atm. Published values of the solubility of a gas are usually for a partial pressure of 1 atm. When corrected to 1 atm, the calculated solubility is in line with published values.

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