Question

1. Compute the concentration of oxygen that will dissolve in seawater at equilibrium with the earth's atmosphere at 15oC. (Chlorinity of seawater = 19g/L or 19,000mg/L.

Answer 1

in order to find out the concentration of dissolved oxygen in sea water at equillibrium we need to find out the salinity,Salinity is defined as the number of non-carbonate salts dossolved in water even though there are other ions but 91% of chlorine ions present in sea water.The salinity level is fairly constant which is 35ppt(35,000 mg/L).The following formula is used for calculating salinity-salinity(ppt)=0.0018066*Cl^- (mg/Cl)=0.0018066*19000=34.3254ppt

Relationships have been derived if temperataure and salinity are given-

ln [O₂] (ml/L) = A₁ +A₂(100/T)+A₃ ln (T/100)+ A₄(T/100)+S[B₁ + B₂(T/100)+ B₃(T/100)²

where:T=288k(15 degree celcius as given)

• A₁ = -173.4292
• A₂ = 249.6339
• A₃ = 143.3483
• A₄ = -21.8492
• B₁ = -0.033096
• B₂ = 0.014259
• B₃ = -0.0017000.after substituting the values answer would be as

-173.4292+249.6339(100/288)+143.3483*1.0577+(-21.8492)(288/100)+34.3254[-0.033096+0.014259(288/100)+(-0.0017000)(288/100)=1.9427mL/l