1 Acids, Bases, and Salts All are electrolytes. 2 Mr. Sharp playing with acids and bases.
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Transcript of 1 Acids, Bases, and Salts All are electrolytes. 2 Mr. Sharp playing with acids and bases.
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Acids, Bases,
and SaltsAll are electrolytes
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Mr. Sharp playing with acids and bases
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The Solubility Product
Ksp
Used for sparingly or slightly soluble salts
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Insoluble Salts and Compounds
A compound may be said to be “Insoluble” in water, but there are always a few particles or ions that do dissolve.
A compound is said to be: insoluble if less that 0.1 of a gram of it will
dissolve in 100 grams of water slightly soluble if between 0.1 and 1.0 grams of it will
dissolve in 100 grams of water soluble if more that 1.0 grams of it will dissolve in
100 grams of water
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Silver chloride is a sparingly soluble salt Its equilibrium reaction is:
• AgCl(s) Ag+(aq) + Cl-(aq)
Its equilibrium expression is:• Keq = [Ag+] [Cl-] / [AgCl]
The concentration for all pure liquids and solids is constant; therefore [AgCl] becomes part of the Keg which we call Ksp, , the solubility product.• Ksp = [Ag+] [Cl-]
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Value of Ksp gives a general idea of how insoluble a substance may be in water
See figure 17-6 on page 566 in Text
In general, the larger the Ksp value the more soluble the substance will be
In general, the smaller the Ksp value the less soluble the substance will be
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General Ksp for any compound AbCd
Equilibrium equation:• AbCd bA+d + dC-b
Equilibrium expression(Ksp)• Ksp = [A+d]b [C-b]d
• Like practice problems 17-1; 2,6,10
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Practice problem 1 Text page565 Equilibrium equation:
• Ag2CrO4 2Ag+1 + CrO4-2
Ksp Expression:
• Ksp = [Ag+1]2 [CrO4-2]
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Practice Problem 2 Text page 565 Equlibrium equation:
• PbI2 Pb+2 + 2I-1
Ksp expression:
• Ksp = [Pb+2] [I-1]2
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Finding Ksp , given ion concentration Practice problem 3 text page 567
Like practice problems 17-1; 14,18 Equilibrium equation: Cd(OH)2 Cd+2 + 2OH-1
Ksp expression: Ksp = [Cd+2] [OH-1]2
Given [Cd+2] = 1.7 x 10-5; therefore, [OH-1] = 2[Cd+2] = 2(1.7 x 10-5) = 3.4 x 10-5
Ksp= (1.7 x 10-5) (3.4 x 10-5)2 = 2.0 x 10-14
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Practice problem 4 Text page 567
Equilibrium equation: Ce(OH)3 Ce+3 + 3OH-1
Ksp expression: Ksp = [Ce+3] [OH-1]3
Given: [Ce+3] = 5.2 x 10-6; therefore, [OH-] = 3[Ce+3] = 3(5.2 x 10-6) = 1.56 x 10-5
Ksp = (5.2 x 10-6)(1.56 x 10-5 )3 = 2.0 x 10-20
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Finding concentration given Ksp
Practice problem 5 Text page 570
Equilibrium equation: CaF2 Ca+2 + 2F-
Ksp expression:
Ksp = [Ca+2] [F-]2 = 3.9 x 10-11
Let [Ca+2] = x and [F-] = 2xTherefore Ksp = (x)(2x)2 = 3.9 x 10-11
4x3 = 3.9 x 10-11; x3 = (3.9 x 10-11)(4)x3 = 9.75 x 10-12; x = (9.75 x 10-12) [Ca+2] = x = 2.1 x 10 -4 ; [F-] = 2x = 4.2 x 10-4
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Practice problem 6 Text page 570 Like practice problems 17-1;
22,26,30 Equilibrium equation: BaCrO4 Ba+2 + CrO4
-2
Ksp = [Ba+2] [CrO4] = 2.0 x 10-10
Let x = [Ba+2] = [CrO4]; therefore (x) (x) = x2 = 2.0 x 10-10
x = (2.0 x 10-10)½ = 1.4 x 10-5
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Properties of Acids
Taste sour (we test not taste) Turns blue litmus red Neutralizes bases and
basic(metallic)oxides React with metals like Zn to produce
hydrogen gas Solution in water are electrolytes Examples:HCl, HNO3, H2SO4,
HCH3COO (CH3COOH) (HC2H3O2)
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Propeties of Bases
Taste bitter(we test not taste) Feel slippery Turn red litmus blue Neutralize acids and acidic(nonmetallic)
oxides Solutions in water are electrolytes Corrosive Examples: NaOH, KOH, Ca(OH)2, NH3
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Acid and Base Theories
Arrhenius - 1887
Bronsted-Lowery - 1923
Lewis - 1923
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Arrhenius Theory Acids - substances that ionize in
water to produce hydrogen ions(H+)
Bases - substances that ionize in water to produce hydroxide ions(OH-)
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Arrhenius Examples Arrhenius Acids:
HCl H+ + Cl-
HNO3 H+ + NO3-
Arrhenius Bases: NaOH Na+ + OH-
Ca(OH)2 Ca2+ + 2OH-
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Bronsted-Lowry Theory
Acids - substances that donate protons(Proton donors)
Bases - substances that accept protons(Proton acceptors)
Hydrogen ions are really the same as protons
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Hydronium Ion(hydrogen ion riding piggy-back on a water molecule)
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Bronsted-Lowry Example: Water acting as an acid
Ammonia + water yield ammonium ion plus hydroxide ion
NH3 + H2O NH4+ + OH-
base acid conjugate conjugate
acid base
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Bronsted Lowry Example:Water acting as a base
Acid base Conjugate acid conjugate base
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Amphiteric = being able to act as an acid or base
acid = proton donor
base = proton acceptor
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Lewis Theory Acids - substances that accept
electron-pairs
Bases - substances that donate electron-pairs
Must draw electron dot formula to determine
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Lewis example:
Lewis base Lewis acid
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Lewis Example
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Lewis Example:
Lewis Lewis acid base
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Lewis Theory is most inclusive, but we will use Bronsted-Lowry, mostly
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Naming Binary Acids Made up of Hydrogen and a
nonmetal (two elements) Use prefix of hydro Use the nonmetal as the root of
the name Add suffix of ic Example: HCl = hydrochloric
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Practice Naming Acids
HBr HI HF H2O H2S H2Te H2Se
hyrdobromic acid hydroiodic acid hydrofluoric acid hydroxyic acid hydrosulfuric acid hydrotelluric acid hydroselenic acid
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Naming Oxyacids Name most common acid in family
with the root of nonmetal other than oxygen then add suffix of ic
Acid of family with one more oxygen than most common add prefix of per and suffix of ic
Acid with one less oxygen than most common use suffix of ous
Acid with two less oxygens than most common add prefix of hypo and keep suffix of ous
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Naming tertiary(oxyacids) Use chlorine oxyacid family as a guide:
HClO4 (one more O) per means more than
HClO3 (most common)
HClO2 (one less O)
HClO (two less O’s) hypo means less than
perchloric acid
chloric acid
chlorous acid
hypochlorous acid
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Naming oxyacids
H2SO4(most common) H2SO3
HNO3(most common) HNO2
HBrO4
HBrO3(most common) HBrO2
HBrO
Sulfuric acid sulfurous acid nitric acid nitrous acid perbromic acid bromic acid bromous acid hypobromous acid
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Naming Arrhenius bases Name positive ion first. Then add
name hydroxide last NH4OH = ammonium hydroxide KOH = potassium hydroxide Ca(OH)2 = calcium hydroxide Mn(OH)7 = manganese(VII)
hydroxide
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Practice Naming bases LiOH
Ba(OH)2
Al(OH)3
Sn(OH)4
Lithium hydroxide
barium hydroxide
aluminum hydroxide
tin(IV) hydroxide
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Anydrides means without water
Acid anhydride = an acid without water(nonmetallic oxides SO2 + H2O H2SO3
N2O5 + H2O 2HNO3
Basic anydride = base without water(metallic oxides) BaO + H2O Ba(OH)2
Na2O + H2O 2NaOH
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Determining anhydride by subtracting water H2SO4 - H2O = SO3
2HNO3 - H2O = N2O5
2H3AsO4 - 3H2O = As2O5
Ba(OH)2 - H2O = BaO 2NaOH - H2O = Na2O 2Al(OH)3 - 3H2O = Al2O3
All H atoms must add out
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Acids and bases neutralize each other
acid + base salt + water parent parent child + water
acid base salt
1. HCl + NaOH NaCl + H2O
2. HClO4 + NaOH NaClO4 + H2O
3. HClO3 + NaOH NaClO3 + H2O
4. HClO2 + NaOH NaClO2 + H2O
5. HClO + NaOH NaClO + H2O
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Rules for naming salts Named from parent acid and base First name comes from parent base Second name comes from parent acid
Salts from binary acids end in ide Salts from oxyacids:
Salt from most common, use suffix of ate Salt from one more oxygen use per prefix and ate suffix Salt from one less oxygen use ite suffix Salt from two less oxygens use hypo prefix and ite suffix
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Practice naming salts from slide #38 NaCl
NaClO4
NaClO3
NaClO2
NaClO
sodium chloride
sodium perchlorate
sodium chlorate
sodium chlorite
sodium hypochlorite
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More Practice naming salts: Go to slide #39 to answer the following
KBrO3
Mn2(SO4)7
CuSO3
Mg(BrO4)2
BaI2 LiBrO NaNO3
KNO2
Potassium bromate manganese(VII) sulfate copper(II) sulfite magnesium perbromate barium iodide lithium hypobromite sodium nitrate potassium nitrite
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Strong acids and bases
Strong acids and bases are nearly 100% ionized HCl + H2O H3O+ + Cl-
If 0.10 mole of HCl are placed in water, we get 0.10 mole of H3O+
NaOH Na+ + OH-
If 0.02 mole of NaOH are place in water we get 0.02 mole of OH-
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Weak acids and bases Weak acids and bases are only slightly
ionized HC2H3O2 + H2O H3O+ + C2H3O2
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Weak acid produces very few H3O+, [H3O+] must be calculated
NH3 + H2O NH4+ + OH-
Weak base produces very few OH-, [OH-] must be calculated
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Self Ionization of water
H2O + H2O H3O+ + OH-
Keq = [ H3O+ ] [ OH-] / [ H2O]2
multiply each side by [H2O]2 and let Keq[H2O]2 = Kw
Kw = [ H3O+] [ OH-] = 1.00 x 10-14
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Concentration of ions in pure water
In pure water [H3O+] = [OH-] = 10-7 M
In an acid solution, [H3O+] > [OH-]
In a basic solution, [H3O+] < [OH-]
In a neutral solution [H3O+] = [OH-]
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Calculating [OH-] or [H3O+] Given that [OH-] = 4.78 x 10-12,
determine the [H3O+] and if the solution is acidic or basic.
[[H3O+] [OH-] = 1 x 10-14
[H3O+] = (1 x 10-14) [OH-] [H3O+] = (1 x 10-14) / (4.78 x 10-12) = 2.09 x 10-3
[H3O+] > [OH-] therefore solution is acidic
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Solving # 2, 19-1 Practice problems
[H3O+] [OH-] = 1 x 10-14
[OH-] = 1 x 10-8
[H3O+] = (1 x 10-14) (1 x 10-8)
[H3O+] = 1 x 10-6 M [H3O+] > [OH-], therefore solution is
acid
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pH is a method of expressing the acidity of a
water solution
pH = -log[H3O+] [H3O+] = 10-pH
In pure water, pH = 7; neutral In acid solution, pH < 7 In basic solution, pH > 7
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Logs are exponents of 10 log(1000) = 3 log(100) = 2 log(10) = 1 log(1) = 0 log(.1) = -1 log(.01) = -2 log(.001) = -3 Log(4.3 x 10-4) = -3.37 log(8.97 x 10 -12) = -11.05
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Using calculator to find logs
Put number into the calculator and push log button
Find log(2.76 x 10-8) = -7.56
Because 10-7.56 = 2.76 x 10-8
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Solving
Solving # 12 on 19-1 Practice problems
[H3O+] = 2.51 x 10-5 , given pH = -log[H3O+] pH = -log(2.51 x 10-5) pH = -(-4.60) = 4.60 pH < 7, therefore solution is acidic
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Acid-Base Indicators
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More indicators
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Most indicators are Weak organic acids, like litmus
HIn(aq) + H2O(l) H3O+(aq) + In-
(aq)
Acid Conjugate Base
Adding an acid(H3O+) will shift equilibrium to the left toward red
Adding a base (OH-) will shift equlibrium to the right toward blue
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Acid-base titration
Standard solution = solution of known concentration(M)
Titrated solution = solution of unknown concentration
Endpoint = condition where an equivalent amount of standard solution as been add to the titrated solution. [H3O+] = [OH-]
Indicator used to find endpoint
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Titration calculations
MaVa = MbVb , where Ma = molarity of the acid Mb = molarity of the base Vb = volume of base used Va = volume of acid used
When MaVa = MbVb , the endpoint has been reached and [H3O+] = [OH-], which means equivalent amounts of acid and base
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Example of titration calculation, page 638 text
Practice #5 Vb= 43.0 mL; Va = 32.0 mL Ma = 0.100; Mb = ?
MaVa = MbVb Mb=MaVa ÷ Vb
Mb= (0.100M)(32.0 mL) ÷ 43.0 mL
Mb = 0.0744 M
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Titration calculation Practice problem #6
Worked the same way as #5 except H2SO4 contains two moles of acid ions per mole of
acid the molarity of the acid must be mltiplied by 2
2MaVa = MbVb Mb= 2MaVa÷ Vb
Mb = 2(0.120M)(25mL) ÷ 40. mL Mb = 0.15 M
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Calculating Ka for a weak acid Practice problem #1, page 613 in text
HCOOH + H2O H3O+(aq) + HCOO-
(aq)
Ka= [H3O+] [HCOO-] ÷ [HCOOH] Initial conc. of acid = 0.100 M Final conc of [H3O+] = 0.0042 M Final conc. of acid is (0.100 - 0.0042) M [H3O+] = [HCOO-] = 0.0042 M Ka = [0.0042] [0.0042] ÷ [0.0958] = 1.8 x 10-4