1. Acids and Bases
PGCC CHM 101 Sinex

2. General properties ACIDS Taste sour Turn litmus
React with active metals – Fe, Zn
React with bases
BASES
Taste bitter
Turn litmus
Feel soapy or slippery (react with fats to make soap)
React with acids
blue to red
red to blue

3. Definitions Acids – produce H+ Bases - produce OH- Acids – donate H+
Bases – accept H+
Acids – accept e- pair
Bases – donate e- pair
Arrehenius
only in water
Bronsted-Lowry
any solvent
Lewis
used in organic chemistry,
wider range of substances

4. Examples The hydrogen ion in aqueous solution
H H2O  H3O+ (hydronium ion)
Examples
Arrhenius
HCl
NaOH
Bronsted-Lowry
HCl
HCN
NH3
Lewis
BF3
:NH3

5. The Bronsted-Lowry Concept
Conjugate pairs
HCl Cl-
CH3COOH CH3COO-
NH NH3
HNO3 NO3-
How does a conjugate pair differ?
H+ transfer

6. Neutralization HCl + NaOH  NaCl + HOH HCl + Mg(OH)2 
In general: Acid Base  Salt + Water
All neutralization reactions are double displacement reactions.
HCl NaOH  NaCl HOH
HCl Mg(OH)2 
H2SO NaHCO3 

7. How are (H+) and (OH-) related?
Does pure water conduct electrical current?
Water is a very, very, very weak electrolyte.
H2O  H OH-
How are (H+) and (OH-) related?
(H+)(OH-) = 10-14
For pure water: (H+) = (OH-) = 10-7M
This is neutrality and at 25oC is a pH = 7.
water

8. Let’s examine the behavior of an acid, HA, in aqueous solution.
CHM 101
Let’s examine the behavior of an acid, HA, in aqueous solution.
Sinex HA
What happens to the HA molecules in solution?

9. 100% dissociation of HA HA H+ Strong Acid A-
Would the solution be conductive?

10. Partial dissociation of HA
Weak Acid A-
Would the solution be conductive?

11. At any one time, only a fraction of the molecules are dissociated.
HA  H A- HA H+
Weak Acid A-
At any one time, only a fraction of the molecules are dissociated.

12. Strong and Weak Acids/Bases
Strong acids/bases – 100% dissociation into ions
HCl NaOH
HNO3 KOH
H2SO4
Weak acids/bases – partial dissociation, both ions and molecules
CH3COOH NH3

13. pH acid rain (NOx, SOx) pH of 4.2 - 4.4 in Washington DC area
0-14 scale for the chemists 2 3 4 5 6 7 8 9 10 11 12
acidic
(H+) > (OH-)
25oC
(H+) = (OH-)
distilled water
basic or alkaline
(H+) < (OH-)
normal rain (CO2)
pH = 5.3 – 5.7
fish populations
drop off pH < 6 and to zero pH < 5
natural waters pH =

14. When life goes either way amphoteric (amphiprotic) substances
Acting like
a base
Acting like an acid
HCO3-
+ H+
- H+
H2CO3
CO3-2
accepts H+
donates H+

15. pH The biological view in the human body acidic basic/alkaline saliva1 2 3 4 5 6 7 8 9 10 11
saliva
blood
urine
gastric juice
vaginal fluid
pancreatic juice
bile
cerebrospinal fluid
Tortora & Grabowski, Prin. of Anatomy & Physiology, 10th ed., Wiley (2003)

16. Show how water can be amphoteric.

17. Dilution Mfinal x Vfinal = Minitial x Vinitial water (solvent) solute
moles of solute remain constant
diluted, Mfinal
Vfinal
molesinitial = molesfinal
Vinitial
concentrated, Minitial
adding water lowers the solute concentration
Mfinal x Vfinal = Minitial x Vinitial

18. Titration Calculation
indicator
HCl NaOH  NaCl HOH
A way to analyze solutions!
at equivalence point: moleHCl = moleNaOH
moles = M x VL
Macid x Vinitial acid = Mbase x Vburet