1. Chemistry Notes: Acids and Bases

2. Properties of Acids and Bases
taste sour (vinegar, lemons)
aqueous solutions of acids are electrolytes
cause indicators to change colors
many metals react with acids to produce H2 gas
react with bases to form a salt and water
most formulas begin with H
bitter taste (soap, unsweetened chocolate)
bases are electrolytes in aqueous solution
cause indicators to change colors
feel slippery
react with acids to form a salt and water
often contain OH- , or ammonia NH3

3. Examples The bolded formulas below to STRONG acids and bases
Common acids
HCl
HNO3
H2SO4
H3PO4
HC2H3O2
H2CO3
Common bases
NaOH
KOH
Ca(OH)2
LiOH
NH3

4. Measuring pH
The pH of a substance can tell us if it’s an acid, a base, or neutral. pH is a measurement of the concentration of hydrogen ions (H+) in a solution. The more hydrogen ions present, the more acidic a substance is.
Acids have large amounts of hydrogen ions, and low pH (pH < 7).
Bases have small amounts of hydrogen ions, and high pH (pH > 7).

5. Another measurement, pOH, tells use the concentration of hydroxide (OH-) ions in a solution. The more hydroxide ions present, the more basic a substance is.
Acids have small amounts of hydroxide ions, and high pOH (pOH > 7).
Bases have large amounts of hydroxide ions, and low pOH (pOH < 7).
Neutral substances have equal amounts of hydrogen and hydrogen ions (pH = 7, pOH = 7).
The pH and pOH of a substance always add up to 14.

7. Practice: Are these solutions acidic, basic, or neutral?
 pH = NH3
Large concentration of OH- ions   Small concentration of H+ ions
pOH = pH = pOH
H2SO4 NaOH
Large concentration of H+ ions HCl

8. Practice: Are these solutions acidic, basic, or neutral?
If the pH of a solution is 6, what is its pOH? Is it an acid or base?
If the pH of a solution is 4, what is its pOH? Is it an acid or base?
If the pOH of a solution is 3, what is its pH? Is it an acid or base?

9. Indicators
Indicators are substances that change color in solutions of different pH
Help determine approximate pH

10. Phenolphthalein
Colorless in acid
Pink in base

11. Universal indicator Mixture of indicators
Changes into different colors at each pH (rainbow)
Red/orange in acid, blue/purple in base, green around pH = 7

12. Litmus paper Blue litmus turns red in acid
Red litmus turns blue in base