Acids and

bases

Properties of acids & bases

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15-1 objectives

• List 5 general properties of aqueous acids and bases

• Name common binary acids and oxyacids

• List 5 common industrial and laboratory acids and give 2 properties of each

• Define Arrhenius acids and bases

• Explain the difference between strong

and weak acids and bases

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Properties of Acids

1. Taste sour

2. Change the color of pH indicators

(turn blue litmus paper red)

3. React with active metals to produce hydrogen gas

4. React with bases to produce salts and water

5. Conduct an electric current

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Properties of Bases

1. Taste bitter

2. Change the color of acid-base indicators

(turn red litmus paper blue)

3. Feel slippery

4. React with acids to produce salts and water

5. Conduct an electric current

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Commonly Used AcidsSulfuric acid (H2SO4)

dehydrating agent; batteries; metals, paper; dyes, paints & detergents

Nitric acid (HNO3)stains proteins yellow; very smelly; explosives

Phosphoric acid (H3PO4)fertilizer; ceramics; detergents; flavoring

Hydrochloric acid (HCl)“pickling” metals; food processing; pools; cleaning masonry

Acetic acid (CH3COOH)smelly; vinegar; freezes at 17oC; plastics; fungicide

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Arrhenius Acid & Bases

Arrhenius acid – increases the concentration of hydrogen ions in aqueous solution

HNO3(l) + H2O(l) H3O+(aq) + NO3

-(aq)

The H3O+ ion is called the hydronium ion

Arrhenius base – increases the concentration of hydroxide ions in aqueous solutions

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Strong AcidsStrong acids ionize completely in aqueous

solutions and are strong electrolytes

Examples:

H2SO4

HClO4

HCl

HNO3

HBr

HI

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Weak Acids

Do not ionize completely and are weak electrolytes

Examples:

H3PO4

CH3COOH

H2CO3

H2S

HCN

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Strong Bases

A strong base completely dissociates in water to produce OH- ions

Solutions are called alkaline

Examples:

NaOH

KOH

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Weak Bases

Weak bases do not dissociate completely in solution

Example:

NH3

C6H5NH2 (aniline)

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Acid-Base Theories

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15-2 Objectives

• Define and recognize Brønsted-Lowry acids and bases

• Define a Lewis acid and a Lewis base

• Name compounds that are acids under the Lewis definition but are not acids under the Brønsted-Lowry definition

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Brønsted-Lowry Acids

• A molecule or ion that is a proton donor is Brønsted-Lowry acid

Example:

HCl dissolved in ammonia

HCl dissolved in water

H2O dissolved in ammonia

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Brønsted-Lowry Bases

• A molecule or ion that accepts a proton is a Brønsted-Lowry base

Example:

HCl dissolved in ammonia

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Monoprotic Acids

Monoprotic acids can donate only one proton

Example:

HCl(g) + H2O(l) H3O+(aq) + Cl-(aq)

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Polyprotic Acids

Polyprotic acids can donate more than one proton

Example:

H2SO4(l) + H2O(l) H3O+(aq) + HSO4

-(aq)

HSO4-(aq) + H2O(l) H3O

+(aq) + SO42-(aq)

This is a diprotic acid (2 ionizations)

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Lewis Acids and Bases

An atom, ion, or molecule that accepts an electron pair to form a covalent bond is a Lewis acid

An atom, ion, or molecule that donates an electron pair to form a covalent bond is a Lewis base

Acid-base reactions

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15-3 Objectives

• Describe a conjugate acid, conjugate base, and amphoteric compound

• Explain the process of neutralization

• Explain how acid rain damages marble surfaces

Amphoteric

• A molecule or ion that can be classified as an acid or a base.

• Ex– HSO4

-

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Conjugate Acids & Bases

The species that remains after a Brønsted-Lowry acid has given up a proton is the conjugate base of that acid.

Example:

base

conjugate acid

(aq)OH aq)(F O(l)H HF(aq) 3-

2

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Conjugate Acids & Bases

The species that is formed when a Brønsted-Lowry base gains a proton is the conjugate acid of that base.

Example:

acid

conjugate base

(aq)OH aq)(F O(l)H HF(aq) 3-

2

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Brønsted-Lowry acid-base reactions are equilibrium systems (can occur both forward and reverse) and involve two acid-base pairs known as conjugate acid-base pairs.

acid base base acid

(aq)OH aq)(F O(l)H HF(aq)

2121

3-

2

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Strength of Conjugate Acids and Bases

The stronger the acid is the weaker its conjugate base

The stronger the base, the weaker its conjugate acid

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Neutralization Reactions

Are reactions between hydronium ions and hydroxide ions to form water

Another product is a salt – a cation from an acid and an anion from a base