Lecture 7 – Ocean Chemistry
1. We talked about C flow from the atmosphere, biosphere etc.
2. There is more C in the soil than in the atmosphere.
3. C in the atoms is the one which motivates us a lot.
Terri Biosphere Atmosphere
Upper Oceans -
Soils Lower Oceans –
40,000 4. How do cO2 get into the oceans, and how to access the lower oceans molecules.
5. If co2 goes into the ocean what would happen?
6. Of co2 was like a simple molecule like N /Ar or a non acid basemolecule then it would be
simple. We know the volume of the ocean, and we can calculate the amount of them. But in
here it is not that simple.
7. Henry’s Law : how much of a gas dissolves in the water.
8. Henry’s law of constant of equilibrium constant describes how much of a gas dissolves in water.
9. If Co2 was like Ar, or N or a non acid- base molecule, then we can say an equilibrium of the
ocean and we can calculate the amount in water. 10. Reaction #3 Co2 +(g) H2C03 (aq) K = 3.4x10^-2
a. Reaction #1 H2Co3 H +HCo3 K=4.5 X10&-7
b. R EACTION #2 HCO3 +CO 32- K A1.7 X10^-11
c. K A1H ][HCO3 ]/[H2 CO 3]=K A1/[H+] ( PH= PKA)
11. KA 1EQUATION SAYS THAT WHEN HCO 3- IS EQUAL TO THE 2 CO3, THAT OCCURS WHEN THE ACIDITY EQUALS TO
THE VALUE OF THE EQUILIBRIUM .WHEN PH = PKA
12. PKA BECOMES VERY USEFUL TO FIND IF THAT ACID IS GOING TO BE PART OF THAT FORM OR NOT .
13. IF THERE CONCENTRATIONS ARE EQUAL THAT ’S WHEN THEIR PKA =PH
14. PKA 1=6.3, PKA 2=10.4,
15. IF WE TAKE CO2 DISSOLVE IN WATER AND FORM CARBONINC ACID ,AND IF THE SOLUTION ENDS UP BEING HIGHLY
ACIDIC,(WITH PH 6.3) THEN THE SPECIES IN CARBONIC ACID.
16. IF THE PH IS HIGER THAN THA,THE SYSTEM SHIFTS OVER TO THE CARBONATE FORM .AT A HIGHER PH,THE SYSTEM
SHIFTS TO THE CARBONATE FORM .THE CROSS OVER BETWEEN BICARBONATE AND CARBONATE IS WHEN PKA = PH
17. pH of the ocean is 8.2. when we start to dissolve water in the ocean then
18. if you start dissolving co2 in water and in order to pull co2 all the way to the form of carbonate,
you have to have a basic solution 19. calculation: when we start to dissolve co2 in ocean we are going to end up mostly with
bicarbonate. This is what the next calculation will show.
20. The most important species we have that we have around to effect this equilibrium is CaCo3.
After co2 gets delivered into the atmosphere from volcanoes, it starts living in the atmosphere,
then it goes to the ocean, where it helps form CaCo3.
21. There are about 10 million units of Co3 in the ocean. It is kind of overwhelming.
22. Because co3 is a base, it will react with water, and form HcO3-. 23. Not a bad assumption, but this shows that most of the carbonate is as bicarbonate.