1. Section 2.5—Characteristics of Acids and Bases
Now that we know what acids are, how do they act?

2. Characteristics of Acids & Bases
Produce H3O+1 (hydronium ion) in water
Produce OH-1 (hydroxide ion) in water
Tastes sour
Tastes Bitter
React with active metals to form hydrogen gas
Feels slippery

3. Strength versus Concentration

4. Review of how acids produce ions-
water
acid
Hydrogen cation with some anion

5. Review of how acids produce ions- +1 H O

6. Review of how acids produce ions- +1 H O
Hydronium ion
Anion

7. Strong versus Weak Acids
How many hydronium ion – anion pairs can you find? - + - 3 +
How many intact acid molecules can you find? + - 1
Strong acid
Most of the acid molecules have donated the H+1 to water

8. Strong versus Weak Acids+
How many hydronium ion – anion pairs can you find? 1
How many intact acid molecules can you find? - 3
Weak acid
Only a few of the acid molecules have donated the H+1 to water

9. Concentrated versus Dilute
solvent
solute
Lower concentration
Not as many solute (what’s being dissolved) particles
Higher concentration
More solute (what’s being dissolved) particles

10. Combinations of Concentration & Strength
Concentrated
Dilute
Strong
A lot of acid added & most dissociates
Not much acid added, but most of what’s there dissociates
Weak
A lot of acid added, but most stays together
Not much acid added and most of what is there stays together

11. Other notes
All of the same ideas apply to bases as well (concentration and strength)
Many people think all acids are dangerous and all bases are more safe
Vinegar is an acid we eat…some of them are safe!
Sodium hydroxide is a very caustic base…not all of them are less harmful than acids!
The stronger and acid or base is (and the more concentrated it is), the more dangerous it is for you

12. pH

13. pH Scale Is a scale to measure the acidity of a sample 1 14 7
Highly acidic
Very basic (not acidic)
neutral 7
Chapter 6 will give more detail about how pH is calculated!

14. Ways to measure pH Indicators change color based on pH
Liquid indicators – various indicators change colors at different pH’s
Universal indicator – a combination of liquid indicators to produce a “rainbow” changing colors at several pH’s
Paper Indicators
Paper with a liquid indicator on it (Litmus paper or pH paper)
pH meters or pH probes
Electronically determine pH and give a read-out

15. Common pH indicators
This picture © 1998 David Dice

16. pH of common substances
0.1M HCl 1
Stomach contents 2
Vinegar
2.9
Soda pop 3
Grapes 4
Beer
4.5
Pumpkin pulp 5
Bread
5.5
Intestinal contents
6.5
Milk
Urine
6.6
Bile
6.9
Saliva 7
Blood
7.4
Eggs
7.8
0.1M NH3 (aq)
11.1
0.1M NaOH 13