1. Unit 6:
ACIDS
BASES
SALTS

2. Acids, Bases, and Salts When dissolved, these compounds ionize
Example: HCl  H+ + Cl-
These charged atoms (ions) are free to move,
so the solutions conduct electricity
Compounds that conduct in solution are
called electrolytes
Strong electrolytes ionize completely;
in weak electrolytes, only some molecules ionize
100
100
HCl  H+ + Cl-
HF  H+ + F-

3. Properties of Acids Properties of Bases -- dilute acids taste sour
-- cause indicators to change color
-- react with many metals to produce
hydrogen gas
Example: 2HCl + Zn  ZnCl2 + H2
-- react with bases to produce water
and a salt neutralization
Properties of Bases
-- dilute bases taste bitter, and feel
soapy
-- cause indicators to change color
-- can neutralize acids to produce
water and a salt

4. Acid/Base Theories 1. Arrhenius
a. acids produce H+ as the only + ion in solution
(or H3O+ -- hydronium ion)
Example: HCl  H+ + Cl-
OR HCl + H2O  H3O+ + Cl-
b. bases produce OH- as the only – ion in solution
Example: Ca(OH)2  Ca OH-
2. Brönsted - Lowry
a. acids can donate a proton to another molecule
(H+)
Example: HBr + H2O  H3O+ + Br-
{HBr donates to H2O}
b. bases can accept a proton (H+) from another molecule
Example: NH3 + H2O  NH OH-
{NH3 accepts from H2O}
Some substances can act as acids or bases, like water (above)

5. Arrhenius Bronsted Summary: Acid Base H+ OH-
proton donor proton acceptor
(lose H+ ) (gain H+ )

6. Acid-Base Reactions Neutralization occurs when H+ + OH-  H2O
acid base water
Neutralization pattern:
Acid Base  Salt Water
Ex. HCl NaOH  NaCl H2O
Ex. H2SO4 + Ca(OH)2  CaSO H2O
1 mole of acid (H+) will neutralize 1 mole of base (OH-)
Example: Suppose you spill 8.0L of 6.0M NaOH. How much
3.0M HCl is required to neutralize it?
Solution: MA VA = MB VB (Table T)
(3.0)(x) = (6.0)(8.0)
x = 16L

7. The solution with the higher molarity will have the smaller volume
You must adjust for the number of H+ or OH- by multiplying the
molarity by the number of moles of ions that will be produced
Example: Ca(OH)2  Ca+2 + 2OH-
for 3M Ca(OH)2, use 6M OH-
Example: H3PO4  3H+ + PO4-3
for 3M H3PO4, use 9M H+
Titration:
a lab procedure that uses neutralization to find the
molarity of an unknown acid or base
obtain a measured amount of acid
with known molarity
2. slowly add base with unknown
molarity--
until the mixture is exactly
neutralized: the end point

8. Example: Suppose you start with 15.0 mL of 2.0M HCl. To
reach endpoint, you add 5.0 mL of unknown NaOH
Solution: MA VA = MB VB
(2.0)(15.0) = (x)(5.0)
x = 6.0M
H2O  H+ + OH-
Water ionizes to a slight extent:
Or, H2O + H2O  H3O+ + OH-
In all aqueous solutions:
[H+ ] x [OH-] = 1 x 10-14
[A] means “the molarity of A”
or “the concentration of A”

9. Any solution: where [H+ ] is greater than [OH-]
= 1 x 10-7
In pure water, [H+ ] = [OH-]
(1 x 10-7 ) x (1 x 10-7) = 1 x 10-14
{to multiply powers of 10, add exponents}
Example: in a 1 x 10-3M solution of HCl, what is [H+]? [OH-]?
Solution: since HCl ionizes completely, [H+] = 1 x 10-3
[H+ ] x [OH-] = 1 x 10-14
(1 x 10-3) x [OH-] = 1 x 10-14
[OH-] = 1 x 10-11
Any solution: where [H+ ] is greater than [OH-]
= Acid
where [H+ ] is less than [OH-]
= Base
where [H+ ] is equal to [OH-]
= Neutral

10. The pH scale -- measures the acidity/basicity of a solution
-- ranges from 0 to 14
very acidic
very basic
-- pH 7 is neutral

11. pH is the negative logarithm of [H+]
-- if [H+ ] = (1 x 10-4),
pH = 4
-- if [H+ ] = (1 x 10-13) ,
pH = 13
Example: What is the pH of pure water?
Solution: [H+ ] = 1 x 10-7
pH = 7
Example: What is the pH of a 1 x 10-2M HCl solution ?
pH = 2
Solution: [H+ ] = 1 x 10-2
Example: What is the pH of a 1 x 10-4M NaOH solution?
Solution: [OH-] = 1 x 10-4
pH = 10
[H+] = 1 x 10-10

12. Some pH values: lemon juice -- 2.3
vinegar
soft drinks
rain (clean)
rain (polluted)
sea water
Example: In a carbonated soft drink, what is [H+]? [OH-]?
Solution: pH = 3, so [H+] = 1 x 10-3M
[OH-] = 1 x 10-11M
Example: How many times more acidic is acid rain, compared to clean?
Solution: Acid, pH Clean, pH 6
1 x 10-3M [H+] x 10-6M
.001M
.001
= times as acidic

13. Since the pH scale is logarithmic; each unit of pH represents a
10x change in acidity [H+]
pH times more acidic than pH 7
= 10 times
= 100 times
= times
Table M can help predict indicator colors at different pH’s
Example: What color would the following indicators be in a
neutral solution?
methyl orange =
yellow
thymol blue =
yellow
bromcresol green =
blue
litmus =
purple?