Question

Be sure to answer all parts. The Henry's law constant (k_H) for in water at 20degreeC is 1.28 x 10^-3 mol/(L*atm). How many grams of will dissolve in 3.50 L of H_2O that is in contact with pure at 1.00 atm? How many grams of O_2 will dissolve in 3.50 L of H_2O that is in contact with air where the partial pressure of CK is 0.209 atm?

Answer 1

Henry's constant k_H = 1.28 x 10^-3 mol / L.atm

a)

pressure = 1.00 atm

Molarity = k_H x pressure

             = 1.28 x 10^-3 x 1

             = 1.28 x 10^-3 M

moles = molarity x volume

           = 1.28 x 10^-3 x 3.5

          = 4.48 x 10^-3

moles = mass / molar mass

4.48 x 10^-3 = mass / 32

mass of O2 = 0.143 g

b)

partial pressure = 0.209 atm

Molarity = k_H x pressure

             = 1.28 x 10^-3 x 0.209

              = 2.68 x 10^-4 M

moles of O2 = Molarity x volume = 2.68 x 10^-4 x 3.50

                    = 9.36 x 10^-4

mass of O2 = moles x mola mass

                   = 9.36 x 10^-4 x 32

                    = 0.030 g

mass of O2 = 0.030 g