Question

The average concentration of nitrogen in open water at 20 degrees C and 1 atm pressure is 18.3 mg/L, Determine the Henrys constant for Nitrogen (N2, Mw 28) in atm -1.

Answer 1

concentration of nitrogen = 18.3 mg/L = 0.183 gm/L

molar mass of N₂= 28 gm/mol that mean 1 mole N₂ = 28 gm then 0.183 gm N₂ = 10.183/28 = 0.0065357 mol

concentration of nitrogen = 0.0065357 mol /L

we know that Henry's law

P = K_HC where, p= partial pressure of solute gas , C= concentration, K_H =henry's constant

nitrogen present 78% in atomosphere thus in 1 atmospheric pressure nitrogens partial pressure is 0.78 atm

P = K_HC thus,

K_H = P/C = 0.78 atm/0.0065357 = 119.34 L atm/mole