1. Unit 4: Acids and Bases
Chapter 8

2. Section 1 Objectives
Describe the ionization of strong acids in water and the dissociation of strong bases in water.
Distinguish between solutions of weak acids or bases and solutions of strong acids or bases.
Relate pH to the concentration of hydronium ions and and hydroxide ions in a solution.

3. What Are Acids? Substances that have a pH lower than 7
Substances that have more H+ ions than OH- ions
Substances that have a sour taste
When dissolved in water, they ionize to form H+ ions
These H+ ions join with the water molecules to form H3O+ (hydronium) ions
Turn blue litmus paper red

4. Strong v. Weak Acids
If an acid ionizes completely in water, it is a strong acid and has a very low pH
The farther from 7 the pH is, the stronger the substance
If a substance does not ionize completely in water, it is a weak acid and has a pH closer to 7
Strong acids are able to conduct electricity when dissolved in water and are called electrolytes

5. Common Acids ACID FORMULA STRENGTH USES Hydrochloric acid HCl Strong
Cleaning, treating metal, adjusting the pH of pools, digestion
Sulfuric acid
H2SO4
Fertilizer, industrial chemical, car batteries
Nitric acid
HNO3
Fertilizers and explosives
Acetic acid
CH3COOH
Weak
Chemicals, plastics, pharmaceuticals, vinegar
Formic acid
HCOOH
Dyes, stinging ants
Citric acid
H3C6H5O7
Flavorings, soft drinks, citrus fruits

6. What Are Bases? Substances that have a pH higher than 7
Substances that have more OH- ions than H+ ions
Substances that taste bitter and feel slippery
When dissolved in water, they ionize to form OH- ions
Strong bases (those with a pH farther from 7) are more conductive of electricity than weak bases (those with a pH near 7)
Not all bases contain OH- ions; some just produce OH- ions when dissolved in water

7. Common Bases BASE FORMULA STRENGTH USES Potassium hydroxide KOH Strong
Soap, absorbing CO2, dyes
Sodium hydroxide
NaOH
Soap, petroleum refining, cleaning drains, synthetic fibers
Calcium hydroxide
Ca(OH)2
Treating acidic soil and lakes, making mortar and cement
Ammonia
NH3
Weak
Fertilizer, making nitric acid, cleaning
Methylamine
CH3NH2
Dyes, medicines, tanning leather
Aniline
C6H5NH2
Dyes, varnishes, solvent

8. What is pH? Determined by using an indicator, such as litmus paper
A measure of the concentration of hydronium (H3O+) ions
pH is very important in living organisms, as many functions can only occur within a very specific range of pH
pH scale ranges from 0 – 14.
Acids are below 7, bases are above 7, and neutral substances (such as water and salts) are right at 7.

9. The pH scale is based on the power of 10
An acid with a pH of 3 is 10x stronger than an acid with a pH of 4
A base with a pH of 9 is 100x weaker than a base with a pH of 11
A small difference in pH can mean a very large difference in acidity or basicity

10. Calculating pH
Concentrations of substances in a solution are written using the units of molarity, or moles of substance per liter of solute
So, if the concentration of H3O+ ions in pure water is mol/L, it can be written as 10 ^-7 M
The pH is the negative of the power of 10
In this example, the pH of the substance would be 7

11. Practice What is the pH of a 10^-4 M solution of bromic acid (HBr)?
What is the pH of a 0.01 M solution of nitric acid (HNO3)?
HBr = 4
HNO3 = 2