Chapter 25: Acids, Bases & Salts. I. Acids and Bases

Chapter 25: Acids, Bases & Salts

I. Acids and Bases

A. Acids

1. produce H+ ions in solution

2. Hydronium ions (H3O+) are then produced when the H+ interacts with water molecules

B. Properties of Acids1. Taste sour (NEVER TASTE AN ACID IN

THE LAB!)2. Corrosive- can “eat” away at metals3. Damage tissue damage by removing

water from them, causing a chemical burn.

Indicators

4. React with indicators- organic compound that changes color in an acid or base (organic means it is a compound that contains carbon) Examples:

a. litmus paper (blue → red = acid; red→ blue =

base)

b. universal indicator c. red cabbage juice d. phenolphthalein e. bromothymol blue

Litmus Paper

AciDs are ReD, and Bases are Blue Blue to red means it is acidic Red to blue means it is basic No change in color means it is

neutral

C. Common Acids

1. Citric acid (in citrus fruits)2. Lactic acid (in milk products)3. Acetic acid (vinegar is acetic acid +

water)

4. Nitric acid5. Sulfuric acid6. Hydrochloric acid7. Carbonic acid8. Phosphoric acid

Writing Formulas for and Naming AcidsIf the anion ends in –ide, add the

prefix hydro- (root of anion) and the ending –ic acid

If the anion ends in ite, change to –ous acid

If the anion ends in –ate, change to –ic acid

Name the following acids:

a. HBrb. H3PO4

c. HFd. HCle. HClO2

f. H2SO4

Check your work:

A. hydrobromic acid B. phosphoric acid C. hydrofluoric acid D. hydrochloric acid E. chlorous acid F. sulfuric acid

Write formulas for these acids:

a. sulfurous acidb. acetic acidc. nitric acidd. nitrous acid

Check your work:

a.H2SO3

b.HC2H3O2

c.HNO3

d.HNO2

More practice

HClO4

Oxalic acidHBrHydrochloric acidHydrosulfuric acid

Acids

Examples; vinegar (acetic acid), citrus fruits (citric acid), stomach acid (hydrochloric acid), aspirin (acetylsalicylic acid); softdrinks (carbonic acid)

Four acids vital in industry: sulfuric, phosphoric, nitric, and hydrochloric acids.

D. Bases

1. Produce hydroxide ions (OH-) in solution

2. Accepts H+ ions from acids

B. Properties of Bases

1. Taste bitter (never taste to check for the presence of a base!)

2. Feel slippery (like soap, which is a base)

3. Corrosive to metals and skin4. Can cause chemical burns5. React with indicators6. Red litmus paper turns blue in the

presence of a base7. Phenolphthalein turns pink

E. Common Bases

1. Antacids: Milk of Magnesia, “TUMS”2. Soap3. Ammonia (a weak base)4. Sodium Hydroxide is used in the

paper industry to separate fibers of cellulose from wood pulp. The freed cellulose fibers are made into paper.

5. Sodium Hydroxide is also in drain cleaners and oven cleaners

II. Strength of Acids and Bases

A. Strong and Weak Acids and Bases 1. Strong Acids-- ionize almost

completely in water a. Examples of Strong Acids: HCl,

HNO3, H2SO4

2. Weak acids- do not completely ionize in solution

a. Examples of Weak Acids: Acetic Acid

Strength of Acids and Bases3. Strong Bases-- ionize almost

completely in water a. Example of a Strong Base: NaOH

4. Weak bases – do not ionize completely in solution

a. Examples of Weak Base: Ammonia

5. Strength vs. Concentrationa. Strong and Weak describe how

completely acids or bases dissociate in water

b. Dilute and Concentrated indicate how much acid or base is dissolved in a solution.

c. It is possible to have diluted solutions of strong acids and concentrated solutions of weak acids

B. pH of a solution

1. measures the concentration of hydrogen ions. The greater the H+ concentration, the lower the pH

2. pH can be measured using a. universal indicator b. pH meter

3. Blood pH is 7.0 – 7.8; range must be maintained for enzymes that act as catalysts for chemical reactions in the body

4. Buffers – solutions containing ions that react with additional acids or bases to minimize the effects of pH (important to keep pH in the correct range, even when acidic foods are eaten)

III. Salts

A. Neutralization

1. A chemical reaction between an acid and a base that takes place in an aqueous solution.

B. Salts

1. Salt- a compound formed when the negative ions from an acid combine with the positive ions from a base.

2. Acid + Base Salt + Water

3. Salts also form as a result of single replacement reactions when acids react with metals.

C. Titration

1. A solution of known concentration, called the standard solution, is added slowly and carefully to a solution of unknown concentration, to which an indicator is added.

2. The Endpoint has a Color

D. Soaps and Detergents1. Soaps clean so well b/c they have a

polar and a nonpolar end2. Soaps are organic salts.3. Commercial Soaps were developed

because simple soaps can react with metal ions in “hard” water, and form soap scum.

4. Detergents a. have long hydrocarbon chains,

like sopas, but instead of carboxylic acid groups, they have either a sulfonic acid or a phosphoric acid.

E. Versatile Esters

1. Esters for Flavor2. Polyesters