1. Acids and Bases

2. Arrhenius’ Definition
Acids give H+ when dissolved in water. Bases give OH- when dissolved in water.

3. Acid or Base?
The measure of the concentration of H+ ions in a solution is called pH
The pH scale measures how acidic or basic a solution is
The scale ranges from -1 to 14
-1 = extremely strong acid
14 = extremely strong base

4. pH Examples

5. Metal + Acid  Salt + H2(g) Acid + Base  Salt + H2O(l)
Properties of Acids
Affects the color of indicators.
React with metals to produce hydrogen gas.
Metal + Acid  Salt + H2(g)
Neutralization of bases to form water.
Acid + Base  Salt + H2O(l)
Taste sour
Citris fruits, vinegar, sour milk are all composed of acids.

6. Strong and Weak Acids Strong acids will completely dissociate.
(all of molecules become ions)
HCl(aq) + H2O(l)  H3O+(aq) + Cl-(aq)
Weak acids do not dissociate easily.
(only a few molecules become ions)
HC2H3O2(aq) + H2O(l)  H3O+(aq) + C2H3O2-(aq)
H3O+ = Hydronium (same thing as H+)
Notice the H+ bonds with the H2O to form H3O+.

7. Examples of Acids Strong Acids HCl Hydrochloric acid
HBr Hydrobromic acid
HI Hydroiodic acid
HNO3 Nitric acid
H2SO4 Sulfuric acid
HClO3 Chloric acid
HClO4 Perchloric acid

8. Examples of Acids Weak Acids H2CO3 Carbonic acid HC2H3O2 Acetic acid
Citric Acid
H2O

9. Mono and Polyprotic acids
Monoprotic Acids
Poly = many
These acids donate more than one H+ (per molecule) when they dissociate
Polyprotic acids ionize in steps
H2S  H+ + HS-
HS-  H+ + S-2
H3PO4  H+ + H2PO4-
H2PO4-  H+ + HPO42-
HPO42-  H+ + PO43-
Mono = 1
These acids donate one H+ (per molecule) when they dissociate
HCl  H+ + Cl-
HNO3  H+ + NO3-

10. Acid + Base  Salt + H2O(l)
Properties of Bases
Affects the color of indicators.
Neutralization of acids to form water.
Acid + Base  Salt + H2O(l)
Taste bitter. (NaHCO3 – Baking Soda)
Feel slippery.

11. Strong and Weak Bases Strong bases: yield OH- in solution.
Group 1a: LiOH, NaOH, KOH, RbOH, CsOH
Group 2a: Ca(OH)2 , Sr(OH)2 , Ba(OH)2
Weak bases do not dissociate in solution,
they just accept a H+
NH3, H2O, CO32-, HClO-
Many others

12. Bronsted-Lowry Definition
Acids are any substance that can donate an H+.
Bases are any substance that can accept an H+.
HCl(g) + H2O(l)  H3O+(aq) + Cl-(aq)
Acid
Proton Donor
Base
Proton Acceptor

13. HCl(g) + H2O(l)  H3O+(aq) + Cl-(aq)
Conjugate Pairs
Reversible reactions have an acid and base on both sides
Pairs that differ by only one proton (H+) are called conjugate pairs
HCl(g) + H2O(l)  H3O+(aq) + Cl-(aq)
Acid
Base
Conjugate
Acid
Conjugate
Base

14. A strong acid will make a weak conjugate base
A weak acid will make a strong conjugate base.
Same for strong & weak bases.

15. What about H2O? Acid or Base?
HCl(g) + H2O(l)  H3O+(aq) + Cl-(aq)
Acid
Base
Conjugate
Acid
Conjugate
Base
NH3(g) + H2O(l)  NH4+(aq) + OH-(aq)
Conjugate
Acid
Acid
Conjugate
Base
Base

16. Water is amphoteric
Amphoteric means a substance can either accept a proton (base) or donate a proton (acid).
Water will act as a base when in solution with an acid
Water will act as an acid when in solution with a base