Acids and Bases

By: Nick Yanik

What we will be learning

• To determine the difference between Acids and Bases

• Discuss the importance of studying acids and bases

What is the pH scale?

• The pH scale measures how Acidic or how Basic a solution is.

The pH scale

• The pH scale is the concentration of hydrogen ions in a given substance

• pH=-log[H+] • Sadly we will not be doing log calculations for

regents chemistry.

Identifying Acids

• Acids have a pH from 0-7• A lower pH value indicates a stronger acid• Neutralizes bases• Corrosive-reacts with most metals to form

Hydrogen gas• Good conductors of electricity• Weak acids do not ionize completely: Acetic, Boric,

Nitrous, Phosphoric, Sulfurous• Strong acids ionize completely: Hydrochloric, Nitric,

Sulfuric, Hydroiodic,

Common Acids

• HCL-Hydrochloric-stomach acid• H2SO4-Sulfuric acid-car batteries• HNO3-nitric acid-explosives• HC2H3O2-acetic acid-vinegar• H2CO3-carbonic acid-sodas• H3PO4-phosphoric acid-flavorings

Identifying Bases

• Bases have a pH from 7-14• A higher pH value indicates a stronger base.• Neutralizes acids• Dissolves fats and oils• Weak Bases-ammonia, potassium carbonate,

sodium carbonate• Strong bases- sodium hydroxide, sodium phosphate,

barium hydroxide, calcium hydroxide

Common Bases

• NaOH-sodium hydroxide (LYE)-soaps, drain cleaner

• Mg(OH)2-magnesium hydroxide-antacids• Al(OH)3-aluminum hydroxide-antacids,

deodorants• NH4OH-ammonium hydroxide-”ammonia”

Arrhenius definition of Acids and Bases

• An Arrhenius acid is a substance that breaks into [H+] ions in an aqueous solution

• An Arrhenius base (alkaline) is a substance that breaks into [OH-] ions in an aqueous solution

• Note: aqueous solution is any solution where H2O is the solvent (the substance in a higher quantity that dissolves the other substance)

Neutral Substances

• What happens when the pH of a substance is 7?

• A pH level of 7 indicates a neutral substance i.e: Water!

Test your knowledge

• What is the range of an acid on the pH scale?• 0-7• What is the range of a base and what is

another name for a base?• 7-14, Alkaline

Characteristics of acids

• Acids can be characterized as:– A sour taste– It turns blue litmus paper red– It tastes sour. Try drinking lemon juice (citric acid)

Characteristics of Bases

• A base is characterized by:– A bitter taste (milk of magnesia)– It feels slippery. (Soapy water)– It turns Red litmus paper Blue

Bronsted-Lowry Acid and Base theory

• A Bronsted-Lowry acid is also considered a “Proton donor” or [H+] donor

• A Brontsted-Lowry base is also considered a “Proton acceptor” or [H+] acceptor

• Conjugate acid-compound formed when a base gains a hydrogen ion

• Conjugate base-compound formed when an acid loses a hydrogen ion

Buffers

• A buffer is a solution that resists changes in pH when small amounts of acids and bases are added

• pH is controlled in situations like: Heartburn, planting vegetables and flowers, fish tanks and ponds, blood, and swimming pools

Acid Rain

• Pollution in the air (Sulfur Dioxide, Carbon Dioxide, Nitrogen Dioxide) combines with water to form various acids