4. Analysis Questions: 1.What does pH measure? the concentration (not “amount”) of hydrogen (H+) ions in a solution. 2.Which pH has the highest concentration of hydrogen ions? 0 lowest concentration of hydrogen ions? 14 3.Which pH has the highest concentration of hydroxide ions? 14 lowest concentration of hydroxide ions? 0

5. Example of “concentration”

6. Indicate whether each of the following “increases” or “decreases”. Fill in the missing arrows. 4. H+ ion concentration INCREASES as pH decreases.pH H+ ____ 5. OH- ion concentration INCREASES as pH increases.pH OH- ____ 6. H+ ion concentration DECREASES as pH increases. pH H+ ____ 7. OH- ion concentration DECREASES as pH decreases. pH OH- ____ 8. At what pH is a substance “neutral”? 7 9.Explain what “neutral” mean in terms of H+ and OH- ions, as demonstrated in the diagram? THE CONCENTRATION OF HYDROGEN IONS IS EQUAL TO THE CONCENTRATION OF HYDROXIDE IONS. H+ = OH-

7. H+ H 2 CO 3 Carbonic acid releases H+ into seawater causing the pH to ______________ Removing H+ from seawater causes the pH to ___________ CO 3 _______ + _________ carbon dioxide water HCO 3 H+ ___________ CaCO 3 _______________ #2 #3 #4 #1 #5 Bicarbonate releases H+ into the seawater, causing the pH to ______________ H2OH2O CO 2 Carbonic Acid DECREASE Bicarbonate Ion Carbonate Ion INCREASE Calcium Carbonate

8. Self-Assessment #1 Carbon Dioxide in the atmosphere, mixes with water to produce carbonic acid. CO 2 + H 2 O  H 2 CO 3 #2 Carbonic acid then disassociates in a H + ion and a bicarbonate ion. H 2 CO 3  H + + HCO 3 H+ released into the seawater causes the pH to decrease.

9. #3 Bicarbonate ions release another H + and becomes a carbonate ion. HCO 3  H + + CO 3 H+ released into the seawater causes the pH to decrease. #4 The carbonate ion can then combine with calcium to form calcium carbonate. CO 3 + Ca  CaCO 3

10. #2 If the pH, becomes basic, then will release H+ which will cause the pH to. H 2 CO 3  H + + HCO 3 increases carbonic acid decrease increase #2 #5

11. #5 If the pH, becomes acidic, ions combine with H + ions to form. HCO 3 + H +  H 2 CO 3 decreases bicarbonate carbonic acid decrease increase #2 #5

12. Releasing H+ ions into seawater, decreasing pH, more acidic Removing H+ ions from seawater, increasing pH, more basic Summary: See Figure 5.18

13. Releasing H+ ions into seawater, decreasing pH, more acidic Removing H+ ions from seawater, increasing pH, more basic Summary: See Figure 5.18

14. Fig. 5.18 Carbonate buffering

17. Ocean acidificationOcean acidification (click for video)