1. What makes an acid an acid or a base a base can vary depending on definition being used. The first definition was created by Svante Arrhenius in 1883. Arrhenius said compounds that will ionize to give off H + ions are acids and compounds that will ionize to give off OH - ions are bases.

2. HCl → H + + Cl - NaOH → Na + + OH - ACID BASE

3. The Bronsted-Lowry definition for a base is that it is an H + acceptor. The definition of an acid is still the same as for Arrhenius - an acid gives off H +

4. HCl + NH 3 → NH 4 + + Cl - ACIDBASE

5. NH 4 + + Cl - → HCl + NH 3 ACIDBASE The equation backwards shows chlorine accepting hyrdrogen., making it a base. In the other equation HCL gave off hydrogen, making it an acid. Therefore we call the pair a conjugate acid-base pair.

6. HCl + H 2 O → H 3 O + + Cl - NH 3 + H 2 O → NH 4 + + OH - Substances that can act as both an acid and base are called amphoteric.

7. H 3 PO 4 + H 2 O → H 2 PO 4 - + H 3 O + H 2 PO 4 - + H 2 O → HPO 4 -2 + H 3 O + HPO 4 -2 + H 2 O → PO 4 -3 + H 3 O + Acids that can give off more than one H + (protons) are called polyprotic. H 3 PO 4 is a triprotic acid, and H 2 SO 4 would be a diprotic acid.

9. A concentrated acid has a lot of acid dissolved in water, and a dilute acid has only a little Strong acids ionize completely, and weak ones only ionize a little.

10. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Strong Acid Weak Acid Weak Base Strong Base

11. To determine the pH of a substance requires an indicator. Indicators are substances that turn colors at certain pH’s.

12. When an acid and base are added together in appropriate amounts, the resulting pH is near 7 - neutral. This is why acids and bases are said to “neutralize” each other. In a neutralization reaction the acid and base (according to the Arrhenius definition) react to form water and a salt.

13. HCl + NaOH → HOH + NaCl WaterSalt

14. Neutralizing an acid and base to determine an unknown amount of H + or OH - is called titration. In a titration a small amount of indicator is added that will change color when the neutralization is complete.