Embed Size (px)
Citation preview
Chapter 19:Chapter 19:Acids and BasesAcids and Bases
Sections 19.1 to 19.4Sections 19.1 to 19.4
Acid PropertiesAcid Properties
• Sour taste (citrus fruits)Sour taste (citrus fruits)
• Conduct electric currentConduct electric current
• Change the color of indicatorsChange the color of indicators
• React with bases to produce salt and React with bases to produce salt and water:water:
HCl + NaOH HCl + NaOH H H22O + NaClO + NaCl
• Some react with metals to release HSome react with metals to release H22 gas: gas:
Mg + HCl Mg + HCl MgCl MgCl22 + H + H22
Naming Acids ReviewNaming Acids Review
• Binary Acids:Binary Acids:– Hydroiodic AcidHydroiodic Acid
•HIHI
– HFHF•Hydrofluoric Hydrofluoric
Acid Acid
•Ternary Acids (oxyacids)
•HClO3
•Chloric Acid
•HClO2
•Chlorous Acid
CATEGORIES OF ACIDSCATEGORIES OF ACIDS
• MonoproticMonoprotic– ONE ionizable HONE ionizable H++ Example: HNO Example: HNO33
• DiproticDiprotic– TWO ionizable HTWO ionizable H++ Example: H Example: H22SOSO44
• TriproticTriprotic– THREE ionizable HTHREE ionizable H++ Example: H Example: H33POPO44
Base PropertiesBase Properties
• Bitter taste (coffee)Bitter taste (coffee)
• Feel slippery (soap)Feel slippery (soap)
• Change the color of indicatorsChange the color of indicators
• Caustic- attack the skin, cause severe Caustic- attack the skin, cause severe burnsburns
• Conduct electric currentConduct electric current
Arrhenius Acids and BasesArrhenius Acids and Bases• Arrhenius AcidArrhenius Acid: : A compound that produces HA compound that produces H++ in solution. in solution.
Ex:Ex: HHCl (g) --------Cl (g) -------- HH++ (aq) + Cl (aq) + Cl- - (aq)(aq)
• Arrhenius BaseArrhenius Base: : A compound that produces OHA compound that produces OH-- in solution. in solution.
Ex: NaEx: NaOHOH (s) --------- (s) --------- Na+ (aq) + Na+ (aq) + OH-OH- (aq) (aq)
H2O
H2O
Acid/Base StrengthAcid/Base Strength
• Strong AcidStrong Acid: Ionizes completely in aq. soln.: Ionizes completely in aq. soln.
HCl H2SO4 HBr HNO3 HI HClO4 HClO3
Strong Bases:
Group 1 and 2 hydroxides
Acid-Base TheoriesAcid-Base Theories
• Bronsted-LowryBronsted-Lowry: expands Arrhenius : expands Arrhenius definition of acids and bases. definition of acids and bases. – Bronsted-Lowry AcidBronsted-Lowry Acid: proton donor: proton donor– Bronsted-Lowry BaseBronsted-Lowry Base: proton acceptor: proton acceptor
ex:ex: HClHCl + + NHNH33 NH NH44++ + Cl + Cl--
Monoprotic B-L Acid
B-L Base
ex2: H3PO4 + H2O H3O+ + H2PO4
-
Which is the B-L Acid? B-L Base?
Lewis Acids and BasesLewis Acids and Bases
• Based on bonding and structure and include Based on bonding and structure and include substances that may not include Hydrogen.substances that may not include Hydrogen.
– Lewis AcidLewis Acid: electron pair acceptor: electron pair acceptor
– Lewis BaseLewis Base: electron pair donor : electron pair donor
ex: ex: BFBF33 (aq) (aq) + + FF-- (aq) (aq) BF BF44-- (aq) (aq)
Draw the dot structure for these substances and Draw the dot structure for these substances and
classify as a Lewis Acid or Base. classify as a Lewis Acid or Base. Lewis Acid
Lewis Base
Conjugate Acids and BasesConjugate Acids and Bases(Based on Bronsted-Lowry (Based on Bronsted-Lowry Classification)Classification)
• Conjugate BaseConjugate Base: The substance that : The substance that remains after an B-L acid has remains after an B-L acid has given upgiven up a a proton (Hproton (H++).).
• Conjugate AcidConjugate Acid: The substance : The substance formed when a B-L base has formed when a B-L base has gainedgained a a proton. proton.
ex: HCl (aq) + H2O (l) Cl- (aq) + H3O+ (aq) Acid Bas
e
Conjugate Base
Conjugate Acid
• Table 19.6: The stronger the acid, the weaker its conjugate base. Equilibrium favors weak acid/base formation.
Acid ReactionsAcid Reactions
• NeutralizationNeutralization: : HCl (aq) + NaOH(aq) HCl (aq) + NaOH(aq) NaCl (aq) + H NaCl (aq) + H22O (l)O (l)
• Acid Formation from Acid AnhydridesAcid Formation from Acid Anhydrides:: SOSO33 (g) (g) + H + H22O (l) O (l) HH22SOSO44 (aq) (aq)
• Base Formation from Basic Anhydrides:Base Formation from Basic Anhydrides: NaNa22OO + H + H22O(l) O(l) 2NaOH 2NaOH
Acid Anhydride Acid Rain
Basic Anhydride
Aqueous Solutions and pHAqueous Solutions and pH
• Self Ionization of WaterSelf Ionization of Water– Water also supplies HWater also supplies H33OO++ and OH and OH-- ions. ions.
HH22O (l) + HO (l) + H22O (l) HO (l) H33OO+ + (aq) + OH(aq) + OH- - (aq)(aq)
1.0 x 10-7 MConductivity Experiments show the concentrations of ions at 25 °C:
1.0 x 10-7 M
• Ionization Constant of Water, KIonization Constant of Water, Kww
KKww = [H = [H33OO++][OH][OH--] = [] = [1.0 x 10-7 M][[1.0 x 10-7 M]
Kw = 1.0 x 10-14 M2
Constant at a given temperature
Neutral, Acidic, and Basic Neutral, Acidic, and Basic SolutionsSolutions
• Neutral:Neutral:[H[H3OO++] = [OH] = [OH--]]
• Acids:Acids:[H[H3OO++] > [OH] > [OH--]]
• Bases:Bases:[H[H3OO++] < [OH] < [OH--]]
Determine the hydronium and hydroxide ion concentrations in a 1 x 10-5 M HCl solution.
pH ScalepH Scale A more convenient way to A more convenient way to
express acidityexpress acidity
• pH = -log[HpH = -log[H33OO++]]• pOH = -log[OH-]pOH = -log[OH-]• pH + pOH = 14.0pH + pOH = 14.0
• Find the pH and pOH of a 1x10Find the pH and pOH of a 1x10-10-10 M solution of HBr. M solution of HBr.
• Find the pH and pOH of a 1x10Find the pH and pOH of a 1x10-10-10 M M solution of HBr. solution of HBr.
1. HBr is an acid so we are looking at the 1. HBr is an acid so we are looking at the [H[H++] concentration.] concentration.
[H[H++] = 1x10] = 1x10-10-10 M M
2. pH = -log[1x102. pH = -log[1x10-10-10]]
pH = 10pH = 10
3. pH + pOH = 143. pH + pOH = 14
10 + pOH = 1410 + pOH = 14
pOH = 4pOH = 4
Calculating pHCalculating pHpH = -log [HpH = -log [H++]]
Ex: A solution has a HEx: A solution has a H++ concentration of concentration of 1x101x10-5-5
pH = -log [1x10pH = -log [1x10-5-5]]
pH = 5 and we have an acidic solutionpH = 5 and we have an acidic solution
Ex: A solution has a pH=8Ex: A solution has a pH=8
8 = -log [H8 = -log [H++]]
[H[H++] = 1 x 10] = 1 x 10-8-8
Indicators and TitrationIndicators and Titration
• Acid-Base IndicatorsAcid-Base Indicators: Compounds : Compounds whose colors are sensitive to pH.whose colors are sensitive to pH.
• Titration:Titration: Method used to determine an Method used to determine an unknown concentration of solution. unknown concentration of solution.
Equivalence PointEquivalence Point• The point at which the 2 solutions The point at which the 2 solutions
used in a titration are present in used in a titration are present in equal amounts.equal amounts.
• End PointEnd Point: The point in a titration : The point in a titration during which an indicator changes during which an indicator changes color. color.
NEUTRALIZATION OF NEUTRALIZATION OF ACIDS & BASESACIDS & BASES
If we need to neutralize an acid or a base, we If we need to neutralize an acid or a base, we use the following formula:use the following formula:
MMaaVVaaCCbb = M = MbbVVbbCCaa
• MMxx=Molarity (mol/L) of the acid or base=Molarity (mol/L) of the acid or base
• VVxx=Volume (L) of the acid or base=Volume (L) of the acid or base
• CCxx =Coefficient (balanced eq.) of the acid =Coefficient (balanced eq.) of the acid or baseor base
MMaaVVaaCCbb = M = MbbVVbbCCaa
Example:Example:
A 25mL solution of HA 25mL solution of H22SOSO44 is neutralized by 18mL of is neutralized by 18mL of a 1.0M NaOH using phenolphthalein as an indicator. a 1.0M NaOH using phenolphthalein as an indicator.
What is the concentration (M) of the HWhat is the concentration (M) of the H22SOSO44??
Step 1: Write the neutralization rxn and balanceStep 1: Write the neutralization rxn and balance
HH22SOSO44 + 2NaOH + 2NaOH Na Na22SOSO44 + + 2H2H22OO
Step 2: Solve for the unknown.Step 2: Solve for the unknown.
MMaa = M = MbbVVbbCCaa (1.0M)(0.018L)(1) (1.0M)(0.018L)(1)
VVaaCCbb (0.025L)(2) (0.025L)(2)
MMaa = 0.36M = 0.36M
