1. Definitions and Indicators
To play the movies and simulations included, view the presentation in Slide Show Mode.

2. Acid/Base Definitions
Definition #1: Arrhenius (traditional)
Acids – produce H+ ions (or hydronium ions H3O+)
Bases – produce OH- ions
Problem: Some bases don’t have hydroxide ions!

3. Arrhenius acid is a substance that produces H+ (H3O+) in water
NH3 doesn’t have hydroxide (OH) in it, so it’s not a base according to Arrhenius, but it still produces OH- and is a base.

4. Acid/Base Definitions
Definition #2: Brønsted – Lowry
Acids – proton donor
Bases – proton acceptor
A “proton” is the same as a hydrogen ion. It’s a hydrogen atom that lost its electron.

5. On the Reactant Side: The Brønsted-Lowry acid is the proton donor
The Brønsted-Lowry base is the proton acceptor
On the Product Side: The Conjugate Acid is the molecule with the additional hydrogen. The Conjugate Base is the molecule that lost the Hydrogen.
conjugate acid
conjugate base
base
acid

6. Identify the Acids, Bases, Conjugate Acids and Conjugate Bases

7. Strong and Weak Acids
Acids are defined as “Strong” or “Weak” by how easily the molecules IONIZE or break apart into its ions.
STRONG ACID: HNO3 (aq) + H2O (l) ---> H3O+ (aq) NO3- (aq)
Strong acids like HNO3 almost 100% ionized in water, which means almost all of the molecules break apart.

8. Strong and Weak Acids
Weak acids like HC2H3O2 only partially ionize water.
Many of the acid molecules stay together and do not break apart.

9. Can you rank these unknown acids in terms of their strength?

10. Strong and Weak Acids/Bases
Strong Base: 100% dissociated in water and create lots of hydroxide ions.
NaOH (aq) ---> Na+ (aq) + OH- (aq)

11. Strong and Weak Acids/Bases
Weak base: Only a few molecules dissociate and very few hydroxide ions are created.
NH3 (aq) + H2O (l)  NH4+ (aq) + OH- (aq)

12. H2O can function as both an ACID and a BASE.
More About Water
H2O can function as both an ACID and a BASE.
H2O + H2O  H3O+ + OH -
When water ionizes, the mole ratio between H3O+ and OH – is the same, so the concentration of ions is the same.
[H3O+] = [OH - ]
Thus why pure water is neutral and not an acid or a base even though it has both ions. They balance each other out perfectly!

13. pH testing There are several ways to test pH
Indicators: Indicators contain chemicals that are receptive and change colors in the presence of acids and bases.
Blue litmus paper (red = acid)
Red litmus paper (blue = basic)
pH paper (multi-colored)
Universal indicator (multi-colored)
Indicators like phenolphthalein
Natural indicators like red cabbage, radishes

14. Paper testing Paper tests like litmus paper and pH paper
Put a stirring rod into the solution and stir.
Take the stirring rod out, and place a drop of the solution from the end of the stirring rod onto a piece of the paper
Read and record the color change. Note what the color indicates.
You should only use a small portion of the paper. You can use one piece of paper for several tests.

15. pH meter Tests the voltage of the electrolyte
Converts the voltage to pH
Very cheap, accurate
The probe must be calibrated before using.