partial pressure of O2 = mole fraction x total pressure
                                     Â
= 0.210 x 1.13
                                     Â
= 0.2373 atm
Henry's law constant = 1.30 × 10^-3 M/atm.
concentration of O2 = 1.30 × 10^-3 x 0.2373
                                 Â
= 3.085 x 10^-4 M
Molarity = moles / volume
3.085 x 10^-4 = moles / 5
moles of O2 = 1.54 x 10^-3
moles = mass / molar mass
1.54 x 10^-3 = mass / 32
mass of O2 = 0.0493 g
