Page 1
11The Chemistry of The Chemistry of Acids and BasesAcids and BasesThe Chemistry of The Chemistry of Acids and BasesAcids and Bases
22
Acid and BasesAcid and Bases
33
Acid and BasesAcid and Bases
44
Acid and BasesAcid and Bases
Page 2
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
66
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”
77
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”
88
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”
Page 3
99
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
Page 4
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
Page 5
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
Page 6
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)
Page 7
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++
Page 8
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
Page 9
3333
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
Page 10
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
Page 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?
Page 12
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?
Page 13
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.
Page 14
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.