Question

calcuate the concentration of dissolved oxygen (unit of mol/L and mg/L of water is equilibrated with pure oxygen at 25⁰C at 1.0 atm.

Answer 1

Henry’s law states that, “at a constant temperature the amount of gas dissolved in a given liquid is proportional to the partial pressure of the gas.” The mathematical equation is given as follows:

P=kC

Where, C = concentration of gas in liquid phase

P = partial pressure of gas

k = Henry’s constant

The value of k for oxygen gas is 770 atm/M. Substitute k = 770 atm/M and P = 1 atm in Henry’s equation.

1 atm = (770 atm/M) x C

C = (1 atm) / (770 atm/M)

C = 0.0013 M

C = 0.0013 mol/L

The molar mass of oxygen gas is 32 g/mol. Conversion factor for converting g into mg is (1000 mg/1 g). Calculate molar mass of oxygen in mg/L

Molar mass of oxygen = 32 g/mol x (1000 mg/1 g)

Molar mass of oxygen = 32,000 mg/mol

Calculate concentration of 0.0013 mol/L of oxygen in mg/L as follows:

Concentration of oxygen = (0.0013 mol/L) / (32,000 mg/mol)

Concentration of oxygen = 41.6 mg/L

Therefore, concentration of dissolved oxygen is 0.0013 mol/L or 41.6 mg/L.