1. Acids and Bases
Everyday Chemistry!
IVORY

2. Properties of Acids and Bases
have a sour taste. (Remember, never taste a chemical in the lab!)
react with many metals to produce H2 (g).
conduct electricity.
turn litmus paper red.
start with H (HCl, HNO3, H2SO4, etc.)
Examples?

3. Properties of Bases IVORY Bases: are sometimes called alkalis
have a bitter taste. (Again, no tasting!)
are generally smooth and slippery feeling.
do not react with metals.
conduct electricity.
turn litmus paper blue.
often (but not always) end in -OH (hydroxide).
Examples?
IVORY

4. The pH Scale Acids have a pH from 0-6.9 Bases have a pH from 7.1-14
Neutral solutions have a pH of 7.0
pH is based on the amount of H+ ion in a solution.

6. What’s “H+” got to do with it?
There are two definitions for acids and bases.
The Arrhenius Definitions:
Acid - a substance that dissociates to produce hydrogen ions (H+) in water.
ex. HCl(aq) --> H+(aq) + Cl-(aq)
Base - a substance that dissociates to produce hydroxide ions (OH-) in water.
ex. NaOH(aq) --> Na+(aq) + OH-(aq)

7. Definition #2 BrØnsted - Lowry Definition
H+ is a naked proton (no electrons), so:
Acid - Any substance that can donate H+ ions. A proton donor.
ex. H2SO4 (aq) --> H+ (aq) + HSO3- (aq)
Base - Any substance that can accept H+ ions. A proton acceptor
ex. NH3(g) + H2O(l) --> NH4+(aq) + OH-(aq)

8. Water--Acid or Base? neutral base? acid?
It can behave like an acid and a base-amphoteric
Lose an H+ to become a hydroxide ion (OH-)
Gain an H+ to become a hydronium ion (H3O+)
2H2O (l)  H3O+(aq) + OH-(aq)
neutral
base?
acid?

9. pH Calculations [H+] [OH-]
pH is based on the concentration of H+ ion in a solution. The formula is:
pH = -log[H+]
Or it may be rearranged to:
[H+] = 10-pH (10 to the power of -pH)
So, since pure water has pH = 7:
[H+]H2O = 1.0 x M
Acid------Neutral-----Base
[H+]
[OH-]

10. Example Calculations
The concentration of hydrogen ions in a solution is 5.21 x 10-2 M. What is its pH?
pH = -log[H+]
= -log(5.21 x 10-2 M)
= 1.28
Calculate [H+] for a solution with a pH of 8.32.
[H+] = 10-pH =
= 4.8 x 10-9 M

11. Strong & Weak Acids
Strong Acid - an acid that dissociates fully into ions:
HA(aq)  H+(aq) + A-(aq)
ex. hydrochloric acid , sulfuric acid, nitric acid
Weak Acid - an acid that has an equilibrium with both the original acid compound and ions:
HA (aq)  H+(aq) + A-(aq)
ex. acetic acid, carbonic acid, phosphoric acid

12. Strong & Weak Bases
Strong Base - a base that dissociates fully into ions:
BOH(aq)  B+(aq) + OH-(aq)
ex. sodium hydroxide, potassium hydroxide, ammonia (B-L base--written differently)
Weak Base - an base that has an equilibrium with both the original base compound and ions:
BOH(aq)  B+(aq) + OH-(aq)
ex. calcium hydroxide

13. Acid + Base ==> ??
Acids and bases neutralize each other. When equal amounts of H+ and OH- come together, they make H2O!
Acid + Base --> Salt + Water
ex. HCl (aq) + NaOH (aq) --> NaCl (aq) + H2O(l)
Acid plus a Base
make a Salt plus Water!

14. Buffers
Buffers:
A buffer is a mixture of chemicals that resists a change in pH.
Therefore, a buffer is at a “set” pH.
These contain weak acids and their salts.
There are buffers keeping your blood at pH =

15. Indicators
A chemical that shows whether something is an acid or base by changing color over a relatively narrow pH range.
ex. Phenolphthalein -- used in alkali metals experiment; showed that the water turned basic by turning pink
ex. Natural indicators: Hydrangeas (see picture), brewed tea, cabbage juice

16. What else are we doing in this unit?
Naming Acids and Bases
Calculating pH, pOH, [H+], [OH-]
Write neutralization reactions
IVORY