1. I. Intro to Acids & Bases Definitions Properties Uses
Ch Acids & Bases
I. Intro to Acids & Bases
Definitions
Properties
Uses

2. HCl + H2O  H3O+ + Cl– A. Definitions Acids
Substances that donate hydrogen ions (H+) form hydronium ions (H3O+) in water
HCl + H2O  H3O+ + Cl–

3. Properties of Acids sour taste corrosive electrolytes turn litmus red
react with metals to form H2 gas
Strength of acid depends on how well they form H+ in water.
pH less than 7

4. Some examples of Acids HNO3 + H2O  H3O+ + NO3-
Nitric acid water hydronium ion nitrate ion

5. Some Examples of Acids

6. Digesting Your Food
Your stomach contains two strong acids: HCl (hydrochloric acid and pepsin).

7. More examples of Acids ACIDS
H3PO4 - soft drinks, fertilizer, detergents
H2SO4 - fertilizer, car batteries
HCl - gastric juice
HC2H3O2 - vinegar
ACIDS

8. Bases
A base is a substance that either contains hydroxide ions-OH-, or reacts with water to form hydroxide ions.
NH3 + H2O  NH4+ + OH-
Hydroxide

9. Properties of Bases bitter taste corrosive electrolytes
turn litmus blue
slippery feel
pH greater than 7

10. Some examples of Bases KOH  K+ + OH- Many soaps contain bases!
potassium hydroxide -> potassium ion plus hydroxide
Many soaps contain bases!

11. Some Common Bases & Uses
NaOH - lye, drain and oven cleaner, hair relaxers
Mg(OH)2 - laxative, antacid- “MOM” Milk of magnesia
NH3 - cleaners, fertilizer
Al(OH)3 aluminum hydroxide Maalox (antacid)

12. Strengths of Acids and Bases
Strong Acid/Base
100% ions in water
strong electrolyte
HCl, HNO3, NaOH, LiOH
Weak Acid/Base
few ions in water
weak electrolyte
HC2H3O2, NH3 - + - +

13. Concept Test!
Which of the following "molecular" pictures best represents a concentrated solution of the weak acid HA? A. B.

14. pH Scale- measuring the strength of acids and bases
a measure of the concentration of H3O+ ions in solution
measured with a pH meter or an indicator with a wide color range 7
INCREASING
ACIDITY
NEUTRAL
BASICITY 14

15. The pH scale is a way of expressing the strength of acids and bases
The pH scale is a way of expressing the strength of acids and bases. Instead of using very small numbers, we just use the NEGATIVE power of 10 on the Molarity of the H+ (or OH-) ion. Under 7 = acid = neutral Over 7 = base

16. pH of Common Substances
0-3 strong acids 4-6 weak acids weak bases strong bases
pH pH pH pH

17. pH Testing Indicator substance that changes color in an acid or base
Examples:
Litmus paper - red/blue
phenolphthalein - colorless/pink
goldenrod - yellow/red
red cabbage juice (natural indicator)- pink/green

18. Neutralization Reactions
When an acid and a base react, they produce a salt and water.
Acid + Base  salt + water
HCl + NaOH  NaCl + H2O
The pH of the products will be nearly neutral or 7.0.
Neutralization to the rescue! When a strong acid is spilled in the lab, it can be neutralized using a base – like baking soda.
When a strong base is spilled, it can be neutralized using an acid-like vinegar.
Both will produce salt-water with a pH of near 7.0.

19. A common neutralization reaction!
People use antacids such as Tums or Rolaids to neutralize stomach acid (HCl) from overeating and drinking.
Antacids are weak bases. Baking soda and water can also be used.
What do these weak antacids do to the excess stomach acid?