How Much Acid is Too Much? Target 7-2

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

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 ____________

What We Know The pH of normal ocean water is 8.1-8.2 The pH of the oceans now is 8.0-8.1 Rivers keep the ocean pH stable by ____________

What We Know The pH of normal ocean water is 8.1-8.2 The pH of the oceans now is 8.0-8.1 Rivers keep the ocean pH stable by acting as a buffer

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

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

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

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

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

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

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

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.

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

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