acids and bases
TRANSCRIPT
Acids and Bases
http://www.unit5.org/chemistry/Acids.htm
http://www.chalkbored.com/lessons/chemistry-11/acid-bronsted.ppt
pH scale
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
ACID BASE
NEUTRAL
Each step on pH scale represents a factor of 10.
pH 5 vs. pH 6 (10X more acidic)pH 3 vs. pH 5 (100X different)pH 8 vs. pH 13 (100,000X different)
: measures acidity/basicity
10x10x10x100x
pH scale
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
ACID BASE
NEUTRAL
Each step on pH scale represents a factor of 10.
pH 5 vs. pH 6 (10X more acidic)pH 3 vs. pH 5 (100X different)
: measures acidity/basicity
10x10x10x100x
Søren Sorensen(1868 - 1939)
Acid vs. Base
AcidAcid
pH > 7
bitter taste
does notreact with
metals
pH < 7
sour taste
react withmetals
Alike Different
Related toH+ (proton)
concentration
pH + pOH = 14
Affects pHand
litmus paper
BaseBase
Different
Topic Topic
Properties
electrolytes
turn litmus red
sour taste
react with metals to form H2 gas
slippery feel
turn litmus blue
bitter taste
ChemASAP
vinegar, milk, soda, apples, citrus fruits
ammonia, lye, antacid, baking soda
electrolytes
Common Acids and Bases
Strong Acids (strong electrolytes)
HCl hydrochloric acidHNO3 nitric acidHClO4 perchloric acidH2SO4 sulfuric acid
Weak Acids (weak electrolytes)
CH3COOH acetic acidH2CO3 carbonic
Strong Bases (strong electrolytes)
NaOH sodium hydroxideKOH potassium hydroxideCa(OH)2 calcium hydroxide
Weak Base (weak electrolyte)
NH3 ammonia
Kotz, Purcell, Chemistry & Chemical Reactivity 1991, page 145
NH4OH ammonia
NH3 + H2O NH4OH
Acid + Base SaltSalt + Water
HCl + NaOH NaCl + HOH
salt water
Neutralization
NeutralizationNeutralization is a chemical reaction between an acid and a base to produce a salt (an ionic compound) and water.
NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)base acid salt water
Some neutralization reactions:
H2SO4(aq) + NaOH(aq) Na2SO4 + HOH
sulfuric acid sodium hydroxide sodium sulfate water
HC2H3O2(aq) + Ca(OH)2(aq) Ca(C2H3O2)2 + HOH
acetic acid calcium hydroxide calcium acetate water
2 2
2 2
Acid-Base Neutralization
1+ 1-
+ +
Hydronium ion Hydroxide ion
H3O+ OH-
Water
H2O
Water
H2O
Water
H2O
Water
H2O
Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 584
Acid-Base Neutralization
1+ 1-
+ +
Hydronium ion Hydroxide ion Water
H3O+ OH- H2O
Water
H2O
Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 584
Formation of Sulfuric Acid
Kelter, Carr, Scott, Chemistry A World of Choices 1999, page 302
SO2(g) + H2O(l) H2SO3(aq)
2SO2(g) + O2(g) 2SO3(g)
SO3(g) + H2O(l) H2SO4(aq)
SO2(g) + H2O2(l) H2SO4(aq)
Catalyzed by atmospheric dust
Sulfuric acid
+
+
Figure courtesy of the National Atmospheric Deposition Program, Champaign, Ill.
The progressively darker red areas on the map indicate the lowest pH levels and areas most prone to problems from acid rain.
Hydrogen ion concentration as pH from measurementsmade at the field laboratories during 2003
National Atmospheric Deposition Program/National Trends Networkhttp://nadp.sws.uiuc.edu
made at the Central Analytical Laboratory, 1999
Acid Rain
Smoke stacks pollute SO2
into the atmosphere. Thiscombines with water to formacid rain.
Estimated sulfate ion deposition, 1999
CO2 (g)CO2 (g) H2O (l)H2O (l) H2CO3 (aq)H2CO3 (aq)
Carbon dioxideCarbon dioxide
Carbonic acid
Carbonic acid
WaterWater
Weak acid Weak acid
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
Common Acids
Sulfuric Acid H2SO4
Nitric Acid HNO3
Phosphoric Acid H3PO4
Hydrochloric Acid HCl
Acetic Acid CH3COOH
Carbonic Acid H2CO3
Battery acid
Used to make fertilizersand explosives
Food flavoring
Stomach acid
Vinegar
Carbonated water
Common AcidsFormulaFormula Name of Acid Name of Negative
Ion of Salt
HF hydrofluoric fluorideHBr hydrobromic bromideHI hydroiodic iodideHCl hydrochloric chlorideHClO hypochlorous hypochloriteHClO2 chlorous chloriteHClO3 chloric chlorateHClO4 perchloric perchlorateH2S hydrosulfuric sulfideH2SO3 sulfurous sulfiteH2SO4 sulfuric sulfateHNO2 nitrous nitriteHNO3 nitric nitrateH2CO3 carbonic carbonateH3PO3 phosphorous phosphiteH3PO4 phosphoric phosphate
Formation of Hydronium Ions
1+
hydronium ion
H3O+
+
hydrogen ion
H+
water
H2O
1+
(a proton)
1+
Sulfuric Acid, H2SO4
Sulfuric acid is the most commonly produced industrial chemical in the world.
Uses: petroleum refining, metallurgy, manufacture of fertilizer, many industrial processes: metals, paper, paint, dyes, detergents
Sulfuric acid is used in automobile batteries.
H2SO4
“oil of vitriol”
Nitric Acid, HNO3
Nitric acid stains proteins yellow (like your skin).
Uses: make explosives, fertilizers, rubber, plastics, dyes, and pharmaceuticals.
HNO3
“aqua fortis”
O
OO
N H
Hydrochloric Acid, HCl
The stomach produces HCl to aid in the digestion of food.
Uses: For ‘pickling’ iron and steel.Pickling is the immersion of metals in acid solution to removesurface impurities.
A dilute solution of HCl is called muriatic acid (available in many hardwarestores). Muriatic acid is commonly used to adjust pH in swimming pools and in the cleaning of masonry.
HCl(g) + H2O(l) HCl(aq)hydrogen chloride water hydrochloric acid
Common Bases
Sodium hydroxide NaOH lye or caustic soda
Potassium hydroxide KOH lye or caustic potash
Magnesium hydroxide Mg(OH)2 milk of magnesia
Calcium hydroxide Ca(OH) 2 slaked lime
Ammonia water NH3 H2O household ammonia
Name Formula Common Name
.NH4OH
NH41+ + OH1-
ammonium hydroxide
hydroxideion
OH1-
Relative Strengths of Acids and Bases
perchloric HClO4
hydrogen chloride HClnitric HNO3
sulfuric H2SO4
hydronium ion H3O+
hydrogen sulfate ion HSO4-
phosphoric H3PO4
acetic HC2H3O2
carbonic H2CO3
hydrogen sulfide H2Sammonium ion NH4
+
hydrogen carbonate ion HCO3-
water H2Oammonia NH3
hydrogen H2
Dec
reas
ing
Aci
d S
tren
gth
perchlorate ion ClO4-
chloride ion Cl-
nitrate ion NO3-
hydrogen sulfate ion HSO4-
water H2Osulfate ion SO4
2-
dihydrogen phosphate ion H2PO4-
acetate ion C2H3O2-
hydrogen carbonate ion HCO3-
hydro sulfide ion HS-
ammonia NH3
carbonate ion CO32-
hydroxide ion OH-
amide ion NH2-
hydride ion H-
Dec
reas
ing
Bas
e S
tren
gth
AcidAcid Formula Formula Conjugate base Conjugate base FormulaFormula
Metcalfe, Williams, Catska, Modern Chemistry 1966, page 229 acid conjugate base + H+
Binary Hydrogen Compoundsof Nonmetals When Dissolved in Water
(These compounds are commonly called acids.)
The prefix hydro- is used to represent hydrogen, followed by the nameof the nonmetal with its ending replaced by the suffix –ic and the wordacid added.
Examples:
*HCl
HBr
*The name of this compound would be hydrogen chloride if it was NOT dissolved in water.
Hydrochloric acid
Hydrobromic acid
Naming Ternary Compounds from Oxyacids
The following table lists the most common families of oxy acids.
one moreoxygen atom
most“common”
one lessoxygen
two lessoxygen
HClO4
perchloric acid
HClO3
chloric acid
HClO2
chlorous acid
HClOhypochlorous acid
H2SO4
sulfuric acid
H2SO3
sulfurous acid
H3PO4
phosphoric acid
H3PO3
phosphorous acid
H3PO2
hypophosphorous acid
HNO3
nitric acid
HNO2
nitrous acid
(HNO)2
hyponitrous acid
An acid with aname ending in
A salt with aname ending in
-ic
-ous
-ate
-iteforms
forms
Hill, Petrucci, General Chemistry An Integrated Approach1999, page 60
Oxyacids Oxysalts If you replace hydrogen with a metal, you have formed an oxysalt.A salt is a compound consisting of a metal and a non-metal. If thesalt consists of a metal, a nonmetal, and oxygen it is called anoxysalt. NaClO4, sodium perchlorate, is an oxysalt.
HClO4
perchloric acid
HClO3
chloric acid
HClO2
chlorous acid
HClOhypochlorous acid
NaClO4
sodium perchlorate
NaClO3
sodium chlorate
NaClO2
sodium chlorite
NaClOsodium hypochlorite
OXYACID OXYSALT
ACID SALT
per stem ic changes to per stem ate
stem ic changes to stem ate
stem ous changes to stem ite
hyper stem ous changes to hypo stem ite
HClO3 + Na1+ NaClO3 + H1+
acid cation salt
Arrhenius Acids and BasesAcids release hydrogen ions in water.Bases release hydroxide ions in water.
An acid is a substance that produces hydronium ions, H3O+, when dissolved in water.
Lewis DefinitionsA Lewis acid is a substance than can accept (and share) an electron pair.A Lewis base is a substance than can donate (and share) an electron pair.
Lewis Acid
Brønsted-Lowry DefinitionsA Brønsted-Lowry acid is a proton donor; it donates a hydrogen ion, H+.A Brønsted-Lowry base is a proton acceptor; it accepts a hydrogen ion, H+.
Brønsted-Lowry
Arrheniusacids
Acid Definitions
Acid – Base Systems
Type Acid Base
Arrhenius H+ or H3O + producer
OH - producer
Brønsted-
Lowry
Proton (H +) donor
Proton (H +) acceptor
Lewis Electron-pair acceptor
Electron-pair donor
Arrhenius Acid
1+
+ +
hydronium ion
H3O+
1-
chloride ion
Cl-
water
H2O
hydrogen chloride
HCl
(an Arrhenius acid)
Any substance that releases H+ ions as the only positive ion in the aqueous solution.
Definitions
• ArrheniusArrhenius - In aqueous solution… - In aqueous solution…
HCl + H2O H3O+ + Cl– •AcidsAcids form hydronium ions (H3O+)
H
HH H H
H
ClClO O
–+
acidCourtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Definitions
• ArrheniusArrhenius - In aqueous solution… - In aqueous solution…
•BasesBases form hydroxide ions (OH-)
NH3 + H2O NH4+ + OH-
H
H
HH H
H
N NO O–+
H
H
H H
baseCourtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Brønsted-Lowry Acids and Bases
1+
+
hydronium ion
H3O+
1-
chloride ion
Cl-
(base)
H2O
(acid)
HCl
+ -
Acid = any substance that donates a proton.
Base = any substance that accepts a proton.
Brønsted-Lowry Acids and Bases
1+
+
hydronium ion
H3O+
1-
chloride ion
Cl-
(base)
H2O
(acid)
HCl
+ -
Acid = any substance that donates a proton.
Base = any substance that accepts a proton.
Definitions
• Brønsted-LowryBrønsted-Lowry
HCl + H2O Cl– + H3O+
•AcidsAcids are proton (H+) donors.
•BasesBases are proton (H+) acceptors.
conjugate acidconjugate base
baseacid
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Definitions
F -
H2PO4-
H2O
HF
H3PO4
H3O+
Give the conjugate base for each of the following:
Polyprotic - an acid with more than one H- an acid with more than one H++
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
pH of Common Substances
Timberlake, Chemistry 7th Edition, page 335
1.0 MHCl0
gastricjuice1.6
vinegar2.8
carbonated beverage3.0
orange3.5
apple juice3.8
tomato4.2
lemonjuice2.2 coffee
5.0
bread5.5
soil5.5
potato5.8
urine6.0
milk6.4
water (pure)7.0
drinking water7.2
blood7.4
detergents8.0 - 9.0
bile8.0
seawater8.5
milk of magnesia10.5
ammonia11.0
bleach12.0
1.0 MNaOH(lye)14.0
8 9 10 11 12 14133 4 5 621 70
acidic neutral basic[H+] = [OH-]
pH of Common Substance
14 1 x 10-14 1 x 10-0 0 13 1 x 10-13 1 x 10-1 1 12 1 x 10-12 1 x 10-2 2 11 1 x 10-11 1 x 10-3 3 10 1 x 10-10 1 x 10-4 4 9 1 x 10-9 1 x 10-5 5 8 1 x 10-8 1 x 10-6 6
6 1 x 10-6 1 x 10-8 8 5 1 x 10-5 1 x 10-9 9 4 1 x 10-4 1 x 10-10 10 3 1 x 10-3 1 x 10-11 11 2 1 x 10-2 1 x 10-12 12 1 1 x 10-1 1 x 10-13 13 0 1 x 100 1 x 10-14 14
NaOH, 0.1 MHousehold bleachHousehold ammonia
Lime waterMilk of magnesia
Borax
Baking sodaEgg white, seawaterHuman blood, tearsMilkSalivaRain
Black coffeeBananaTomatoesWineCola, vinegarLemon juice
Gastric juice
Mor
e ba
sic
Mor
e ac
idic
pH [H1+] [OH1-] pOH
7 1 x 10-7 1 x 10-7 7
pH Calculations
pH
pOH
[H3O+]
[OH-]
pH + pOH = 14
pH = -log[H3O+]
[H3O+] = 10-pH
pOH = -log[OH-]
[OH-] = 10-pOH
[H3O+] [OH-] = 1 x10-14
pH = - log [H+]
pH = 4.6
pH = - log [H+]
4.6 = - log [H+]
- 4.6 = log [H+]
- 4.6 = log [H+]
Given:
2nd log
10x
antilog
multiply both sides by -1
substitute pH value in equation
take antilog of both sides
determine the [hydronium ion]
choose proper equation
[H+] = 2.51x10-5 M
You can check your answer by working backwards.
pH = - log [H+]
pH = - log [2.51x10-5 M]
pH = 4.6
Recall, [H+] = [H3O+]
Acid Dissociation
monoproticmonoprotic
diproticdiprotic
polyproticpolyprotic
HA(aq) H1+(aq) + A1-(aq)
0.03 M 0.03 M 0.03 M
pH = - log [H+]
pH = - log [0.03M]
pH = 1.52e.g. HCl, HNO3
H2A(aq) 2 H1+(aq) + A2-(aq)
0.3 M 0.6 M 0.3 M
pH = - log [H+]
pH = - log [0.6M]
pH = 0.22e.g. H2SO4
Given: pH = 2.1
find [H3PO4]
assume 100% dissociation
e.g. H3PO4
H3PO4(aq) 3 H1+(aq) + PO43-(aq)
? M x M
pH = ?
Given: pH = 2.1
find [H3PO4]
assume 100% dissociation
H3PO4(aq) 3 H1+(aq) + PO43-(aq)
X M 0.00794 M
Step 1) Write the dissociation of phosphoric acid
Step 2) Calculate the [H+] concentration pH = - log [H+]
2.1 = - log [H+]
- 2.1 = log [H+]
2nd log - 2.1 = log [H+]2nd log
[H+] = 10-pH
[H+] = 10-2.1
[H+] = 0.00794 M
[H+] = 7.94 x10-3 M7.94 x10-3 M
Step 3) Calculate [H3PO4] concentration
Note: coefficients (1:3) for (H3PO4 : H+)
7.94 x10-3 M3
= 0.00265 M H3PO4
How many grams of magnesium hydroxide are needed to add to 500 mL of H2O to yield a pH of 10.0?
Step 1) Write out the dissociation of magnesium hydroxide Mg2+ OH1-
Mg(OH)2Mg(OH)2(aq) Mg2+(aq) 2 OH1-(aq)+
Step 2) Calculate the pOH pH + pOH = 1410.0 + pOH = 14
pOH = 4.0
Step 3) Calculate the [OH1-] pOH = - log [OH1-]
[OH1-] = 10-OH
[OH1-] = 1 x10-4 M
1 x10-4 M0.5 x10-4 M5 x10-5 M
Step 4) Solve for moles of Mg(OH)2
L
mol M
L 0.5
molx M x105 5- x = 2.5 x 10-5 mol Mg(OH)2
Step 5) Solve for grams of Mg(OH)2
x g Mg(OH)2 = 2.5 x 10-5 mol Mg(OH)2 1 mol Mg(OH)2
= 0.00145 g Mg(OH)2
58 g Mg(OH)2
pH Paper
pH 0 1 2 3 4 5 6
pH 7 8 9 10 11 12 13
Red Cabbage IndicatorCopyright © 2007 Pearson Benjamin Cummings. All rights reserved.
23
24
How to read a buret volume
23.45 mL
(not 24.55 mL)
24.55 mL?
Titration
• TitrationTitration– Analytical method in which
a standard solution is used to determine the concentration of an unknown solution.
standard solution
unknown solutionCourtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
• Equivalence point Equivalence point (endpoint)(endpoint)– Point at which equal amounts of
H3O+ and OH- have been added.
– Determined by…• indicator color change
Titration
• dramatic change in pH
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