1. How Much Acid is Too Much?
Target 7-2

2. What We Know The pH of normal ocean water is_____
The pH of the oceans now is ________
Rivers keep the ocean pH stable by ____________

3. What We Know The pH of normal ocean water is 8.1-8.2
The pH of the oceans now is ________
Rivers keep the ocean pH stable by ____________

4. What We Know The pH of normal ocean water is 8.1-8.2
The pH of the oceans now is
Rivers keep the ocean pH stable by ____________

5. What We Know The pH of normal ocean water is 8.1-8.2
The pH of the oceans now is
Rivers keep the ocean pH stable by acting as a buffer

6. Recap
Acids are substances that increase the amount of H3O+ in a sample

7. Recap Weak Acids: Dissociate partially (not completely)
Stay at equilibrium
Ex) C2H5COOH + H2O <-> C2H5COO- + H3O+

8. Recap When a weak acid dissociates, it creates its conjugate base
Ex) C2H5COOH + H2O <-> C2H5COO- + H3O+

9. Recap
Conjugate Base: a molecule made when an acid loses its acidic hydrogen
Acts like a very weak base
Is able to react with H+ to re-form the original acid

10. Buffers
A buffer solution is a solution containing a weak acid and its conjugate base or a weak base/conj. acid
Solution is at equilibrium
Will react with a strong acid or strong base

11. Buffers
Remember that when acid is added to water, H3O+ ions are formed:
HCl  H+ + Cl-
H+ + H2O  H3O+

12. Buffers
When acid is added to a buffer solution, those H+ ions react with the weak base in the buffer before they react with the water
HCl  H+ + Cl-
H+ + H2O + NaHCO3  NaH2CO3 + H2O
The H3O+ ion doesn’t form, so the pH changes less

13. Demo
We are going to add strong acid to water and to a buffer solution.
Record the pH of each solution after each drop is added.

14. Reflect What happened when we added acid to water?
What happened when we added acid to the buffer?

15. In the Ocean Primary Ocean Buffer System: Na2CO3 + H+ <-> NaHCO3
NaCO3 is formed when:
Carbonate ions (CO32-) from bedrock flow from rivers into the ocean
Carbonate reacts with sodium ions (Na+) from the salt in ocean water