Acids & Bases

Standards:

Chem 5a. Students know the observable properties of acids,

bases, and salt solutions.Chem 5c.

Students know strong acids and bases fully dissociate and weak acids and bases partially dissociate.

What are acids?

Some are dangerous and can burn your skin

Some are safe to eat and drink

Stomach acid helps digest food

Some are dangerous and can burn your skin

Some are safe to eat and drink

Stomach acid helps digest food

Properties of Acids

Acids can be solids, liquids, or gases A group of compounds which behave A group of compounds which behave

similarlysimilarly All have pH below 7All have pH below 7 Turn Litmus paper REDTurn Litmus paper RED In an acidic solution, [H3O+]>[OH-] All donate HAll donate H++ ions in aqueous solution ions in aqueous solution

waterHCl H+(aq) + Cl- (aq)

Acids can be solids, liquids, or gases A group of compounds which behave A group of compounds which behave

similarlysimilarly All have pH below 7All have pH below 7 Turn Litmus paper REDTurn Litmus paper RED In an acidic solution, [H3O+]>[OH-] All donate HAll donate H++ ions in aqueous solution ions in aqueous solution

waterHCl H+(aq) + Cl- (aq)

Properties of Acids

Acids are generally sour in tasteStrong acids and some concentrated weak

acids are corrosive and can cause severe burns.

Generally when you see a compound with “H” in it, i.e. HCl, HCN, it indicates that compound is an acid

In dilute concentrations, acids are responsible for the sour taste in lemons, limes, vinegar & other substances

Acids are generally sour in tasteStrong acids and some concentrated weak

acids are corrosive and can cause severe burns.

Generally when you see a compound with “H” in it, i.e. HCl, HCN, it indicates that compound is an acid

In dilute concentrations, acids are responsible for the sour taste in lemons, limes, vinegar & other substances

Examples of Strong Acids

Strong acids FULLY dissociate into H+ and an anion (negative ion) when they are mixed with H2OHCl - hydrochloric acid HI - hydroiodic acidHNO3 - nitric acid HClO4 - perchloric acidHBr - hydrobromic acid H2SO4 - sulfuric acid

Strong acids FULLY dissociate into H+ and an anion (negative ion) when they are mixed with H2OHCl - hydrochloric acid HI - hydroiodic acidHNO3 - nitric acid HClO4 - perchloric acidHBr - hydrobromic acid H2SO4 - sulfuric acid

Examples of Weak Acids

Weak acids do NOT fully dissociate; they are partially ionized in their solutionsCH3COOH - acetic acid, aka vinegarHF - hydrofluoric acidHCOOH - formic acid, found in

venom of bee & ant stings

Weak acids do NOT fully dissociate; they are partially ionized in their solutionsCH3COOH - acetic acid, aka vinegarHF - hydrofluoric acidHCOOH - formic acid, found in

venom of bee & ant stings

Acid Reactions

Acid + Base Acid + Base Salt + Water Salt + Water Acid + Metal Acid + Metal Salt + Hydrogen Salt + Hydrogen Acid + Carbonate Acid + Carbonate Salt + Water + Salt + Water +

Carbon DioxideCarbon DioxideHydrochloric acids (HCl) form Hydrochloric acids (HCl) form

CHLORIDE saltsCHLORIDE saltsNitric acid (HNONitric acid (HNO33) forms NITRATE ) forms NITRATE

saltssaltsSulfuric acid (HSulfuric acid (H22SOSO44) forms ) forms

SULFATE saltsSULFATE salts

Acid + Base Acid + Base Salt + Water Salt + Water Acid + Metal Acid + Metal Salt + Hydrogen Salt + Hydrogen Acid + Carbonate Acid + Carbonate Salt + Water + Salt + Water +

Carbon DioxideCarbon DioxideHydrochloric acids (HCl) form Hydrochloric acids (HCl) form

CHLORIDE saltsCHLORIDE saltsNitric acid (HNONitric acid (HNO33) forms NITRATE ) forms NITRATE

saltssaltsSulfuric acid (HSulfuric acid (H22SOSO44) forms ) forms

SULFATE saltsSULFATE salts

What are Bases (Alkalis)?

In our home we often use In our home we often use bases to clean things. Ex: bases to clean things. Ex: Bleach and toothpasteBleach and toothpaste

In our home we often use In our home we often use bases to clean things. Ex: bases to clean things. Ex: Bleach and toothpasteBleach and toothpaste

Properties of BasesGenerally when you see a compound

with “OH” in it, i.e. NaOH, KOH, it indicates that compound is a base. OH- = hydroxide

pH greater than 7Have bitter taste, feel slippery to the

touchStrong base can also cause serious

burnsTurn red litmus paper blueAll donate OH- ions in water In a basic solution, [H3O+]<[OH-]

Generally when you see a compound with “OH” in it, i.e. NaOH, KOH, it indicates that compound is a base. OH- = hydroxide

pH greater than 7Have bitter taste, feel slippery to the

touchStrong base can also cause serious

burnsTurn red litmus paper blueAll donate OH- ions in water In a basic solution, [H3O+]<[OH-]

Properties of Bases

Example: H2O + NH3 OH- + NH4+Example: H2O + NH3 OH- + NH4+

H+ donor(acid)

H+ acceptor(base)

Examples of Strong Bases

Strong bases FULLY dissociate into OH- and a cation (positive ion) when they are mixed with H2O

The cations of these strong bases appear in the first & second groups of the periodic table LiOH - lithium hydroxide Mg(OH)2 - magnesium hydroxide NaOH - sodium hydroxide Ca(OH)2 - calcium hydroxideKOH - potassium hydroxide and more..

Strong bases FULLY dissociate into OH- and a cation (positive ion) when they are mixed with H2O

The cations of these strong bases appear in the first & second groups of the periodic table LiOH - lithium hydroxide Mg(OH)2 - magnesium hydroxide NaOH - sodium hydroxide Ca(OH)2 - calcium hydroxideKOH - potassium hydroxide and more..

Examples of Weak Acids

Weak bases do NOT fully dissociateNH3

And more…

Weak bases do NOT fully dissociateNH3

And more…

Learning Check

Describe the solution in each of the following as: 1) acid 2) base or 3)neutral.

A. ______ Soda B. ______ Soap C. ______ Coffee D. ______ Wine E. ______ Water F. ______ Grapefruit

Describe the solution in each of the following as: 1) acid 2) base or 3)neutral.

A. ______ Soda B. ______ Soap C. ______ Coffee D. ______ Wine E. ______ Water F. ______ Grapefruit

Learning Check

Describe the solution in each of the following as: 1) acid 2) base or 3)neutral.

A. _Acid__ Soda B. _Base__ Soap C. _Acid__ Coffee D. _Acid_ Wine E. _Neutral__ Water F. _Acid__ Grapefruit

Describe the solution in each of the following as: 1) acid 2) base or 3)neutral.

A. _Acid__ Soda B. _Base__ Soap C. _Acid__ Coffee D. _Acid_ Wine E. _Neutral__ Water F. _Acid__ Grapefruit

Learning Check

Identify each as characteristic of an A) acid or B) base

A. ____ Sour taste B. ____ Produces OH- in aqueous

solutions C. ____ Produces H+ in aqueous solutions D. ____ Feels slippery to the touch

Identify each as characteristic of an A) acid or B) base

A. ____ Sour taste B. ____ Produces OH- in aqueous

solutions C. ____ Produces H+ in aqueous solutions D. ____ Feels slippery to the touch

Learning Check

Identify each as characteristic of an A) acid or B) base

A. __A_ Sour taste B. __B_ Produces OH- in aqueous

solutions C. __A_ Produces H+ in aqueous solutions D. __B_ Feels slippery to the touch

Identify each as characteristic of an A) acid or B) base

A. __A_ Sour taste B. __B_ Produces OH- in aqueous

solutions C. __A_ Produces H+ in aqueous solutions D. __B_ Feels slippery to the touch

Salt Solutions

Any ionic compound formed from the reaction between an acid and a base

The reaction between an acid and a base is called a neutralization reaction

Far less corrosive than acids or bases from which they are formed

Examples:HCl + NaOH NaCl + H2OHCl + KOH KCl + H2O

Any ionic compound formed from the reaction between an acid and a base

The reaction between an acid and a base is called a neutralization reaction

Far less corrosive than acids or bases from which they are formed

Examples:HCl + NaOH NaCl + H2OHCl + KOH KCl + H2O

Learning Check

Acid, Base or Salt?

A. ______ CaCl2B. ______ KOHC. ______ Ba(OH)2

D. ______ HBrE. ______ H2SO4

Acid, Base or Salt?

A. ______ CaCl2B. ______ KOHC. ______ Ba(OH)2

D. ______ HBrE. ______ H2SO4

Learning Check

Acid, Base or Salt?

A. __salt____ CaCl2B. __base____ KOHC. __base____ Ba(OH)2

D. __acid____ HBrE. __acid____ H2SO4

Acid, Base or Salt?

A. __salt____ CaCl2B. __base____ KOHC. __base____ Ba(OH)2

D. __acid____ HBrE. __acid____ H2SO4

pH Scale

0

Acid7

Base

14

pH of common substances

Acid – Base Concentrations

pH = 3

pH = 7

pH = 11

OH-

H3O+OH-

OH-H3O+

H3O+

[H3O+] = [OH-] [H3O+] > [OH-] [H3O+] < [OH-]

acidicsolution

neutralsolution

basicsolution

co

nc

en

trat

ion

(m

ole

s/L

)

10-14

10-7

10-1

Timberlake, Chemistry 7th Edition, page 332

pH

pH = -log [H+] pH = -log [H+]