1. Acid-Base Reactions
Monday, 4/21/14

2. Acid + Base  Water + Salt
Acid-Base Reactions
When an acid and a base are placed together, they react to neutralize the acid and base properties, producing a salt and water.
The H+ cation of the acid combines with the OH- anion of the base to form water.
The compound formed by the remaining ions is called a salt.
Acid Base  Water + Salt
Ex: HCl + NaOH  H2O + NaCl

3. H2SO4 + Ca(OH)2 → ??? Predicting Products
What are the most likely products of the following acid-base reaction?
H2SO4 + Ca(OH)2 → ???

4. Check: Do the charges on the salt =0 (remember criss-cross)?
Predicting Products
What are the most likely products of the following acid-base reaction?
H2SO4 + Ca(OH)2 → H2O + CaSO4
Check: Do the charges on the salt =0 (remember criss-cross)?

5. Neutralization vs. Buffers

6. Types of Acids and Bases
Strong Acids: completely dissociate (break apart) in solution to form H+ ions.
Strong Bases: completely dissociate in solution to form OH- ions.
Weak Acids: Only partially dissociate; some H+ ions stay bonded to the rest of the acid molecule.
Weak Bases: Only partially dissociate; some OH- ions stay bonded to the rest of the base molecule.

7. Strong Acids and Strong Bases
Both fully ionize (break apart)
The reaction leads to a pH=7 solution, with only the water and salt remaining.

8. Weak Acids and Weak Bases
These do not fully break apart
There is more than just water and salt remaining!
Weak Acid: HA, H+, A-
Example: HCN leads to HCN, H+, and CN-
Weak Base: BOH, OH-, B+
Example: NH4OH leads to NH4OH, NH4+, and OH-

9. Buffer Reactions
Having the extra weak acid and weak base present means that the solution can still neutralize additional acids or bases.
This allows the solution to RESIST a change in pH. Left over weak acid and base neutralizes whatever else is added in!
This is called a “buffer.”

11. If I were to add a base to this kind of solution, there is still acid left to “buffer” a potential change in pH.
It will resist a change in “equilibrium.”

12. Your Job
Complete the Neutralization and Buffer Practice for tomorrow!
We will begin our unit project on Wednesday. (It will be partner/small group)