Acids, Bases, and pHAcids, Bases, and pH

Properties of acidsProperties of acids

1. Sour taste1. Sour taste

2. Contain hydrogen, react with active 2. Contain hydrogen, react with active metals to give off Hmetals to give off H22 gas gas

3. Change the color of indicators3. Change the color of indicators

4. React with bases to produce salts 4. React with bases to produce salts and and

waterwater

e.g. e.g.

2NaOH + H2NaOH + H22SOSO44 → 2H → 2H22O + NaO + Na22SOSO44

5. Acids are electrolytes5. Acids are electrolytes

Traditional definition of an Traditional definition of an acidacid

• A cmpd. That contains hydrogen and A cmpd. That contains hydrogen and ionizes in aqueous soln. to form ionizes in aqueous soln. to form hydrogen ions (Hhydrogen ions (H++))

Common acidsCommon acids

• HCl – hydrochloric acidHCl – hydrochloric acid

• HH22SOSO44 – sulfuric acid – sulfuric acid

• HCHC22HH33OO22 – acetic acid – acetic acid

• HNOHNO33 – nitric acid – nitric acid

• HH33POPO44 – phosphoric acid – phosphoric acid

Sulfuric acidSulfuric acid

• #1 industrial chemical#1 industrial chemical

• Fertilizers, petroleum refining, ……Fertilizers, petroleum refining, ……

• Used as a measure of a country’s Used as a measure of a country’s economyeconomy

Acetic acidAcetic acid

• Dilute acetic acid is vinegarDilute acetic acid is vinegar

Acid PrecipitationAcid Precipitation

• Combustion of fossil fuelsCombustion of fossil fuels– Is the main cause of acid precipitationIs the main cause of acid precipitation

4.6

4.6

4.3

4.1

4.3

4.6

4.64.3

Europe

North America

BasesBases

Properties of basesProperties of bases

1. Bitter taste1. Bitter taste

2. Feel slippery to the skin2. Feel slippery to the skin

3. Change color of indicators3. Change color of indicators

4. React with acids to produce water 4. React with acids to produce water and saltsand salts

e.g.e.g.

2NaOH + H2NaOH + H22SOSO44 → 2H → 2H22O + NaO + Na22SOSO44

5. Bases are electrolytes5. Bases are electrolytes

Traditional definition of a Traditional definition of a basebase

• OHOH-- producer producer

Neutralization reactionsNeutralization reactions

• Reaction of hydronium ions (HReaction of hydronium ions (H33OO++) and ) and hydroxide (OHhydroxide (OH--) ions to form water) ions to form water

HH33OO++ + + OHOH- - 2H2H22OO

HCl + NaOH HCl + NaOH H H22O + NaClO + NaCl

(NaCl is a salt)(NaCl is a salt)

Common basesCommon bases

Sodium hydroxideSodium hydroxide

• ((NaNaOHOH), also known as ), also known as lyelye or or caustic caustic sodasoda, is a , is a causticcaustic metallic metallic basebase. It is . It is widely used in many industries, widely used in many industries, mostly as a strong mostly as a strong chemicalchemical basebase in in the manufacture of the manufacture of pulppulp and and paperpaper, , textilestextiles, , drinking waterdrinking water, , soapssoaps and and detergentsdetergents. Worldwide production in . Worldwide production in 1998 was around 45 million 1998 was around 45 million tonstons. .

pH scalepH scale

pHpH

• - log [H- log [H++]]

• e.g. if [He.g. if [H++] = 1 x 10] = 1 x 10-8-8 MM

pH = 8pH = 8

If [HIf [H++] = 3.4 x 10] = 3.4 x 10-5-5 find pH find pH

= -[(log 3.4 + log 10= -[(log 3.4 + log 10-5-5)])]

= -[(0.53) + (-5)]= -[(0.53) + (-5)]

= -(0.53 – 5)= -(0.53 – 5)

= 4.47= 4.47

If the pH is 2 what is the If the pH is 2 what is the [H[H++]]

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

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

[H[H++] = antilog (-pH)] = antilog (-pH)

= antilog (-2)= antilog (-2)

= 1 x 10= 1 x 10-2 -2 MM

If the pH is 6.4 what is [HIf the pH is 6.4 what is [H++]]

[H[H++] = antilog (-pH)] = antilog (-pH)

= antilog (-6.4)= antilog (-6.4)

= 4.0 x 10= 4.0 x 10-7-7 MM

If the pH is 5.4 what is [HIf the pH is 5.4 what is [H++]]

[H+] = antilog (-pH)[H+] = antilog (-pH)

= antilog (-5.4)= antilog (-5.4)

= 4.0 x 10= 4.0 x 10-6-6 M M

[H[H++] [OH] [OH--] = 1 x 10] = 1 x 10-14-14

• Therefore if [OHTherefore if [OH--] = 1 x 10] = 1 x 10-10-10

pH = 4pH = 4

• if [OHif [OH--] = 1 x 10] = 1 x 10-7-7

pH = 7pH = 7

Diprotic acidDiprotic acid

• Can donate (2) protons (HCan donate (2) protons (H++) per ) per moleculemolecule

• e.g. He.g. H22SOSO44

TriproticTriprotic

• Donates (3) protonsDonates (3) protons

• e.g. He.g. H33POPO44

Normality (Normality (N N ))

= (molarity) x (whole # factor)= (molarity) x (whole # factor)

# equivalents solute / L of solution# equivalents solute / L of solution

What is the normality of a soln w/ What is the normality of a soln w/ 1 mol H1 mol H22SOSO44 dissolved in 1 L of dissolved in 1 L of

soln?soln? 2 2 equivalentsequivalents x 1 x 1 molmol H H22SOSO44 = 2 = 2

equivalentsequivalents

1 1 molmol H H22SOSO4 4 1 1 L L 11 L L

= 2 = 2 NN H H22SOSO44

TitrationTitration

• Controlled addition & measurement Controlled addition & measurement of amt. of soln. of a of amt. of soln. of a knownknown conc. That conc. That is required to react completely with a is required to react completely with a measured amt. of soln. of measured amt. of soln. of unknownunknown conc.conc.

Graph of titration resultsGraph of titration results

SaponificationSaponification

• hydrolysis of an ester under basic hydrolysis of an ester under basic conditions to form an alcohol and the conditions to form an alcohol and the salt of a carboxylic acid. salt of a carboxylic acid. Saponification is commonly used to Saponification is commonly used to refer to the reaction of a metallic refer to the reaction of a metallic alkali (base) with a fat or oil to form alkali (base) with a fat or oil to form soap. soap.