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Using Equilibrium with Calcite and CO2.

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KH = 3.3 x 10-7
Ka1 = 4.5 x 10-7 (carbonic acid)
Ka2 = 4.7 x 10-11 (bicarbonate)
Ksp = 5 x 10-9 (calcite)

Assuming equilibrium between the atmosphere, seawater, and calcite:

[H+]3 = KH2Ka12Ka2PCO22

[HCO3-] = 2Ksp{H+]2

[CO32-] = Ka1Ka2KHPCO2

[Ca2+] = Ksp{H+]2

(a) Predict seawater pH, [CO32-], [Ca2+] at an atmospheric concentration of 280 ppmv
Predict seawater pH, [CO32-], [Ca2+] at an atmospheric concentration of 840 ppmv

(b) How would these changes affect the tendency for calcite or aragonite to dissolve or precipitate from seawater? Explain how this affects the carbonate pump for removing CO2 from the atmosphere?

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Solution Summary

This solution describes how to:

1) Calculate pH, carbonate concentration, calcium concentration given an equilibrium equation and atmospheric CO2 concentration.
2) Explain how pressure impacts the carbonate pump