the chemistry of 1 2 acids and bases - pbworkschemistrydeast.pbworks.com/f/acids bases notes.pdfthe...

11The Chemistry of The Chemistry of Acids and BasesAcids and BasesThe Chemistry of The Chemistry of Acids and BasesAcids and Bases

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Acid and BasesAcid and Bases

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55Acids

Have a sour taste. Vinegar is a solution of acetic acid. CitrusHave a sour taste. Vinegar is a solution of acetic acid. Citrusfruits contain citric acidfruits contain citric acidfruits contain citric acid.fruits contain citric acid.

React with certain metals to produce hydrogen gasReact with certain metals to produce hydrogen gas..

React with carbonates and bicarbonates to produce carbon React with carbonates and bicarbonates to produce carbon dioxide gasdioxide gas

BasesHave a bitter taste.Have a bitter taste.

Feel slippery. Many soaps contain bases.Feel slippery. Many soaps contain bases.

Bases

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Some Properties of Acids

Produce H+ (as H3O+) ions in water (the hydronium ion is a

hydrogen ion attached to a water molecule)

Taste sour

Corrode metals

Electrolytes

React with bases to form a salt and water

pH is less than 7

Turns blue litmus paper to red “Blue to Red A-CID”

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Some Properties of Bases

Produce OHProduce OH-- ions in waterions in water

Taste bitter, chalkyTaste bitter, chalky

Are electrolytesAre electrolytes

Feel soapy, slipperyFeel soapy, slippery

React with acids to form salts and waterReact with acids to form salts and water

pH greater than 7pH greater than 7

Turns red litmus paper to blue “Turns red litmus paper to blue “BBasic asic BBlue”lue”

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Anion

Acid Nomenclature Review

Ending Acid Name-ide hydro-(stem)-ic acid

-ate (stem)-ic acid

No OxygenNo Oxygen

w/Oxygenw/Oxygen

-ite (stem)-ous acid

w/Oxygen w/Oxygen

An easy way to remember which goes with which…An easy way to remember which goes with which…

“In the cafeteria, you “In the cafeteria, you ATEATE something something ICICky”ky”

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Acid Nomenclature Flowchart1010

Nomenclature with an Acid Series

• Name the followingName the following

–HCl–HClO–HClO2

HClO–HClO3

–HClO4

1111

•• HBrHBr (aq)(aq) hydrohydrobromicbromic acidacid

Acid Nomenclature Review

HBr HBr (aq)(aq)

•• HH22COCO33

•• HH22SOSO33

hydrohydrobromicbromic acidacid

carboncarbonicic acidacid

sulfursulfurousous acidacid22 33

1212

Name ‘Em!•• HClHCl ((aqaq))

•• HH22SOSO3322 33

•• HNOHNO33

•• HH22SOSO44

•• HH33POPO33

•• HCIOHCIO22

•• HBrOHBrO33

•• HH33POPO44

1313

Name ‘Em!•• HClHCl ((aqaq)) hydrochloric acidhydrochloric acid

•• HH22SOSO33 sulfurous acidsulfurous acid22 33

•• HNOHNO33 nitric acidnitric acid

•• HH22SOSO44 sulfuric acidsulfuric acid

•• HH33POPO33 phosphorous acidphosphorous acid

•• HCIOHCIO22 chlorouschlorous acidacid

•• HBrOHBrO33 bromicbromic acidacid

•• HH33POPO44 phosphoric acidphosphoric acid

1414

Some Common Bases

NaOHNaOH sodium hydroxidesodium hydroxide lyelye

KOHKOH potassium hydroxidepotassium hydroxide liquid soapliquid soap

BaBa(OH)(OH)22 barium hydroxidebarium hydroxide stabilizer for plasticsstabilizer for plastics

Mg(OH)Mg(OH)22 magnesium hydroxidemagnesium hydroxide “MOM” Milk of magnesia“MOM” Milk of magnesia

Al(OH)Al(OH)33 aluminum hydroxidealuminum hydroxide Maalox (antacid)Maalox (antacid)

NHNH33 ammoniaammonia

1515

Acid/Base definitions

• Definition #1: Arrhenius (traditional)Definition #1: Arrhenius (traditional)

Acids – produce H+ ions (or hydronium ions H3O+)

Bases – produce OH- ions

(problem: some bases don’t have hydroxide ions! Can you name one?)

1616Arrhenius acid is a substance that produces H+ (H3O+) in water

Arrhenius base is a substance that produces OH- in water

1717

Acid/Base Definitions

• Definition #2: Brønsted – LowryDefinition #2: Brønsted Lowry

Acids – proton donor

Bases – proton acceptor

A “proton” is really just a hydrogen atom that has lost it’s electron!

1818A Brønsted-Lowry acid is a proton donorA Brønsted-Lowry base is a proton acceptor

1919

ACIDACID--BASE THEORIESBASE THEORIESACIDACID--BASE THEORIESBASE THEORIES

The Brønsted definition means NHThe Brønsted definition means NH33 is is e ø sted de t o ea se ø sted de t o ea s 33 ssaa BASEBASE in water in water —— and water is and water is itself anitself an ACIDACID

BaseAcidAcidBaseNH4

+ + OH-NH3 + H2OBaseAcidAcidBase

NH4+ + OH-NH3 + H2O

2020

Monoprotic vs. Polyprotic

• What does sulfuric acid do in water?at does su u c ac d do ate

2121Strong and Weak Acids/BasesStrong and Weak Acids/Bases

The strength of an acid (or base) is determined by the amount of IONIZATION

The strength of an acid (or base) is determined by the amount of IONIZATIONIONIZATION.IONIZATION.

HCl, HBr, HI, HNO3, HClO3, H2SO4 and HClO4 are among the only known strong acids.

2222

•• Weak acidsWeak acids are much less than 100% ionized in are much less than 100% ionized in water.water.

Strong and Weak Acids/BasesStrong and Weak Acids/BasesStrong and Weak Acids/BasesStrong and Weak Acids/Bases

One of the best known is acetic acid = CHOne of the best known is acetic acid = CH33COCO22HH

2323

•• Strong Base:Strong Base: 100% dissociated in 100% dissociated in water.water.

Strong and Weak Acids/BasesStrong and Weak Acids/Bases

NaOH (s) NaOH (s) ------> Na> Na+ + (aq) + OH(aq) + OH-- (aq)(aq)

Other common strong bases Other common strong bases include LiOH, KOH, NaOH, include LiOH, KOH, NaOH, RbOH, CsOH, andRbOH, CsOH, and Ca(OH)Ca(OH)22, , Ba(OH)Ba(OH)22, Sr(OH), Sr(OH)22..

2424

•• Weak base:Weak base: less than 100% ionized less than 100% ionized in waterin water

Strong and Weak Acids/BasesStrong and Weak Acids/BasesStrong and Weak Acids/BasesStrong and Weak Acids/Bases

in waterin waterOne of the best known weak bases is One of the best known weak bases is

ammoniaammoniaNHNH3 3 (aq) + H(aq) + H22O (l) O (l) NHNH44

+ + (aq) + OH(aq) + OH-- (aq)(aq)

2525

Conjugate PairsConjugate Pairs2626

PROBLEM: The following reactions are important environmental processes. Identify the conjugate acid-base pairs.

(a) H2PO4-(aq) + CO3

2-(aq) HPO42-(aq) + HCO3

-(aq)

(b) H2O(l) + SO32-(aq) OH-(aq) + HSO3

-(aq)

2727

PROBLEM: Identify the acid / base conjugate pairs

(b) H2O(l) + HS-(aq) OH-(aq) + H2S(aq)

(a) H2PO4-(aq) + NH3(aq) HPO4

2-(aq) + NH4+(aq)

(b) H2O(l) + HS (aq) OH (aq) + H2S(aq)

2828

Learning Check!

Label the acid, base, conjugate acid, and Label the acid, base, conjugate acid, and abe t e ac d, base, co jugate ac d, a dabe t e ac d, base, co jugate ac d, a dconjugate base in each reaction:conjugate base in each reaction:

HCl + OHHCl + OH-- ClCl-- + H+ H22OOHCl + OHHCl + OH-- ClCl-- + H+ H22OO

HH22O + HO + H22SOSO44 HSOHSO44-- + H+ H33OO++HH22O + HO + H22SOSO44 HSOHSO44-- + H+ H33OO++

2929Acids & Base DefinitionsAcids & Base Definitions

Lewis acidLewis acid -- aaDefinition #3 – LewisDefinition #3 – Lewis

Lewis acid Lewis acid -- a a substance that substance that accepts an electron accepts an electron pairpair

Le is baseLe is base aaLewis base Lewis base -- a a substance that substance that donates an electron donates an electron pairpair

3030The The pH scalepH scale is a way of is a way of expressing the strength expressing the strength of acids and bases. of acids and bases. Instead of using very Instead of using very

ll b j tll b j tsmall numbers, we just small numbers, we just use the NEGATIVE use the NEGATIVE power of 10 on the power of 10 on the Molarity of the HMolarity of the H++ (or (or OHOH--) ion.) ion.))

Under 7 = acidUnder 7 = acid7 = neutral7 = neutral

Over 7 = baseOver 7 = base

3131

pH of Common pH of Common SubstancesSubstances

3232Calculating the pH

pH = - log [H+](Remember that the [ ] mean Molarity)

Example: If [H+] = 1 X 10-10

pH = - log 1 X 10-10

pH = - (- 10)pH = 10p

Example: If [H+] = 1.8 X 10-5

pH = - log 1.8 X 10-5

pH = - (- 4.74)pH = 4.74

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Try These!Try These!Find the pH of these:Find the pH of these:1)1) A 0.15 M solution of Hydrochloric acidA 0.15 M solution of Hydrochloric acid

2) A 3.00 X 102) A 3.00 X 10--77 M solution of Nitric acidM solution of Nitric acid2) A 3.00 X 102) A 3.00 X 10 M solution of Nitric acidM solution of Nitric acid

3434

pH calculations pH calculations –– Solving for H+Solving for H+pH calculations pH calculations –– Solving for H+Solving for H+If the pH of Coke is 3.12, [HIf the pH of Coke is 3.12, [H++] = ???] = ???Because pH = Because pH = -- log [Hlog [H++] then] then

-- pH = log [HpH = log [H++]]Take antilog (10Take antilog (10xx) of both) of both

sides and getsides and get

1010--pH pH == [H[H++]][H[H++] = 10] = 10--3.123.12 = 7.6 x 10= 7.6 x 10--44 MM

*** to find antilog on your calculator, look for “Shift” or “2*** to find antilog on your calculator, look for “Shift” or “2nd nd

function” and then the log buttonfunction” and then the log button

3535pH calculations pH calculations –– Solving for H+Solving for H+•• A solution has a pH of 8.5. What is the A solution has a pH of 8.5. What is the

Molarity of hydrogen ions in the Molarity of hydrogen ions in the solution?solution?

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

8.5 = 8.5 = -- log [Hlog [H++]]

--8.5 = log [H8.5 = log [H++]]

A tilA til 8 5 til (l [H8 5 til (l [H++])])

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

8.5 = 8.5 = -- log [Hlog [H++]]

--8.5 = log [H8.5 = log [H++]]

A tilA til 8 5 til (l [H8 5 til (l [H++])])Antilog Antilog --8.5 = antilog (log [H8.5 = antilog (log [H++])])

1010--8.58.5 = [H= [H++]]

3.16 X 103.16 X 10--99 = [H= [H++]]

Antilog Antilog --8.5 = antilog (log [H8.5 = antilog (log [H++])])

1010--8.58.5 = [H= [H++]]

3.16 X 103.16 X 10--99 = [H= [H++]]

3636

More About WaterMore About WaterHH22O can function as both an ACID and a BASE.O can function as both an ACID and a BASE.

In pure water there can beIn pure water there can be AUTOIONIZATIONAUTOIONIZATION

Equilibrium constant for water = KEquilibrium constant for water = Kww

KKww = [H= [H33OO++] [OH] [OH--] =] = 1.00 x 101.00 x 10--1414 at 25 at 25 ooCC

3737More About WaterMore About Water

OH-OH-AutoionizationAutoionization

KKww = [H= [H33OO++] [OH] [OH--] = 1.00 x 10] = 1.00 x 10--1414 at 25 at 25 ooCC

H3O+H3O+

In a In a neutral neutral solution [Hsolution [H33OO++] = [OH] = [OH--]]

so Kso Kww = [H= [H33OO++]]22 = [OH= [OH--]]22

and so [Hand so [H33OO++] = [OH] = [OH--] = 1.00 x 10] = 1.00 x 10--77 MM

3838pOH•• Since acids and bases are Since acids and bases are

opposites, pH and pOH are opposites, pH and pOH are opposites!opposites!

•• pOH looks at the perspective of a pOH looks at the perspective of a basebase

pOH = pOH = -- log [OHlog [OH--]]Since pH and pOH are on opposite Since pH and pOH are on opposite

ends,ends,ends,ends,pH + pOH = 14pH + pOH = 14

3939

pHpH [H+][H+] [OH-][OH-] pOHpOH

4040

[H[H33OO++], [OH], [OH--] and pH] and pHWhat is the pH of the What is the pH of the

0.0010 M NaOH solution? 0.0010 M NaOH solution? [OH[OH ] 0 0010 ( 1 0 X 10] 0 0010 ( 1 0 X 10 33 M)M)[OH[OH--] = 0.0010 (or 1.0 X 10] = 0.0010 (or 1.0 X 10--33 M)M)

pOH = pOH = -- log 0.0010log 0.0010pOH = 3pOH = 3

pH = 14 pH = 14 –– 3 = 113 = 11

4141The pH of rainwater collected in a certain region of the northeastern United States on a particular day was 4.82. What is the H+ ion concentration of the rainwater?

The OH- ion concentration of a blood sample is 2.5 x 10-7 M. What is the pH of the blood?p

4242[OH[OH--]]

[H[H++]] pOHpOH

pHpH

4343Calculating [H3O+], pH, [OH-], and pOHProblem 1: A chemist dilutes concentrated hydrochloric acid to make two solutions: (a) 3.0 M and (b) 0.0024 M. Calculate the [H3O+], pH, [OH-] and pOH of the two solutions at 25°C[OH ], and pOH of the two solutions at 25 C.

4444Calculating [H3O+], pH, [OH-], and pOHProblem 2: What is the [H3O+], [OH-], and pOH of a solution with pH = 3.67? Is this an acid, base, or neutral?

4545Calculating [H3O+], pH, [OH-], and pOHProblem 3: Problem #2 with pH = 8.05?

4646Paper testing•• Paper tests like litmus paper and pH Paper tests like litmus paper and pH

paperpaper–– Put a stirring rod into the solution Put a stirring rod into the solution

and stir.and stir.–– Take the stirring rod out, and Take the stirring rod out, and

place a drop of the solution from place a drop of the solution from the end of the stirring rod onto a the end of the stirring rod onto a piece of the paperpiece of the paper

–– Read and record the color Read and record the color h N t h t th lh N t h t th lchange. Note what the color change. Note what the color

indicates.indicates.–– You should only use a small You should only use a small

portion of the paper. You can use portion of the paper. You can use one piece of paper for several one piece of paper for several tests.tests.

4747

pH meter

•• Tests the voltage of theTests the voltage of theTests the voltage of the Tests the voltage of the electrolyteelectrolyte

•• Converts the voltage to Converts the voltage to pHpH

•• Very cheap, accurateVery cheap, accurate•• Must be calibrated with Must be calibrated with

a buffer solutiona buffer solution

4848

ACIDACID--BASE REACTIONSBASE REACTIONSNeutralizationNeutralization

HCl + NaOHHCl + NaOH NaCl + HNaCl + H22OOHCl NaOH HCl NaOH NaCl HNaCl H22OO

HH22CC22OO44(aq) + 2 NaOH(aq) (aq) + 2 NaOH(aq) ------>>NaNa22CC22OO44(aq) + 2 H(aq) + 2 H22O(l)O(l)acidacid + + base base salt + watersalt + water

What happens if too little acid added? Too much base?

4949

• Calculations:

1.How many milliliters of 1.50 M HCl would be necessary to neutralize 125 mL OF 2.6 M NaOH?

5050

• Calculations:

2. How many milliliters of 4.494 M H2SO4 would be necessary to neutralize 7.2280 grams of LiOH?

5151Setup for titrating an acid with a baseSetup for titrating an acid with a base 5252

TitrationTitrationTitrationTitration1. Add solution from the buret.1. Add solution from the buret.2. Reagent (base) reacts with 2. Reagent (base) reacts with

compound (acid) in solution compound (acid) in solution in the flask.in the flask.

3.3. Indicator shows when exact Indicator shows when exact stoichiometric reaction has stoichiometric reaction has occurred. (Acid = Base)occurred. (Acid = Base)

Used to determine the Used to determine the concentration of an concentration of an unknown.unknown.

535335.62 35.62 mLmL of of NaOHNaOH is neutralized with 25.2 is neutralized with 25.2 mLmL of of

0.0998 M 0.0998 M HClHCl by titration to an equivalence point. by titration to an equivalence point. What is the concentration of the What is the concentration of the NaOHNaOH??

5454

• Find the molarity of a hydrochlic acid solution if 42.0 mL of 0.15 M NaOH are required to neutralize 100.0 mL of the acid.

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