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� Sour taste� React w/ metals to form H2

� Most contain hydrogen� Are electrolytes� Change color in the � presence of indicators � (turns litmus red)� Has a pH lower than 7

� Bitter taste

� Slippery feel

� Are electrolytes

� Change color in the presence of indicators (turns litmus blue)

� Has a pH higher than 7

AcidAcidAcidAcid

•Arrhenius acid =

produces H+ ions

in water

ex. HCl, H3SO4

•0≤pH<7

•Taste: sour

•acid + metal → H2 + salt

BaseBaseBaseBase• Arrhenius base =

produces OH- ions

in water

ex. NaOH, Ca(OH)2

• 7<pH≤14

• Taste: bitter

• feels slippery

• electrolytes• corrosive• pH=7=neutral• salt = ionic compnds w/ no H+ or OH-• neutralization rxn

acid +base →

H2O + salt

� Binary acids:Binary acids:Binary acids:Binary acids: acids that contain only 2 acids that contain only 2 acids that contain only 2 acids that contain only 2 elements; e.g. HFelements; e.g. HFelements; e.g. HFelements; e.g. HF

� Polyatomic acids:Polyatomic acids:Polyatomic acids:Polyatomic acids: acids that contain more acids that contain more acids that contain more acids that contain more than 2 elements; e.g. Hthan 2 elements; e.g. Hthan 2 elements; e.g. Hthan 2 elements; e.g. H2222SOSOSOSO4444

◦ These acids contain polyatomic ionsThese acids contain polyatomic ionsThese acids contain polyatomic ionsThese acids contain polyatomic ions

◦ Also called ternary or oxyAlso called ternary or oxyAlso called ternary or oxyAlso called ternary or oxy---- acidsacidsacidsacids

AcidsAcidsAcidsAcids(begin w/ H+)

Binary

(2 elements)

hydro ic acid

Polyatomic

Ions

ends in –ate

___ic acid

ends in -ite

___ous acid

DON’T ADD HYDRO!!

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� Start with the prefix Start with the prefix Start with the prefix Start with the prefix hydrohydrohydrohydro----� Put it in front of the root word of the anion Put it in front of the root word of the anion Put it in front of the root word of the anion Put it in front of the root word of the anion

((((---- charged ion)charged ion)charged ion)charged ion)� Add Add Add Add ––––icicicic to the endto the endto the endto the end� ExamplesExamplesExamplesExamples◦ Hydrobromic (HBr)Hydrobromic (HBr)Hydrobromic (HBr)Hydrobromic (HBr)◦ Hydrofluoric (HF)Hydrofluoric (HF)Hydrofluoric (HF)Hydrofluoric (HF)◦ Hydroiodic (HI)Hydroiodic (HI)Hydroiodic (HI)Hydroiodic (HI)◦ Hydrochloric (HCl)Hydrochloric (HCl)Hydrochloric (HCl)Hydrochloric (HCl)

� Start with the root word of the name of the Start with the root word of the name of the Start with the root word of the name of the Start with the root word of the name of the polyatomic ionpolyatomic ionpolyatomic ionpolyatomic ion

� Add Add Add Add ––––ousousousous if name ends in if name ends in if name ends in if name ends in ––––iteiteiteite

� Add Add Add Add ----ic ic ic ic if name ends in if name ends in if name ends in if name ends in ––––ateateateate

� Examples:Examples:Examples:Examples:◦ Chlorous (from chlorite, ClOChlorous (from chlorite, ClOChlorous (from chlorite, ClOChlorous (from chlorite, ClO2222

----))))

◦ Nitric (from nitrate, NONitric (from nitrate, NONitric (from nitrate, NONitric (from nitrate, NO3333----))))

◦ Sulfurous (from sulfite, SOSulfurous (from sulfite, SOSulfurous (from sulfite, SOSulfurous (from sulfite, SO3333----2222))))

� Dissociation – when a salt or a base break apart into cations & anions◦ Ex: NaOH (aq) → Na+ (aq) + OH- (aq)

CaI2 (aq) → Ca2+ (aq) + 2I- (aq)

*balancing: subscript of the ion will become the coefficient

� Ionization – when an acid breaks apart in water to produce hydronium ion & an anion◦ Ex: HCl + H2O → H3O

+ + Cl-

*balancing: the number of hydrogens in the acid (subscript)

will be the coefficient for the H2O and the H3O+

� Neutralization rxn: a rxn of an acid and a base in aqueous sol’n to produce a salt and water

� acid + base → H2O + salt

� double displacement reaction

� H+ from acid combines with OH- from base to form HOH = H2O

� Salt: compound formed from the positive ion of a base and a negative ion of an acid

� Properties of the acid and base cancel each other

� Proposed the model in 1887

� Acid: any compound that produces H+ ions in aqueous (water) sol’n

� Base: any compound that produces OH-

(hydroxide) ion in aqueous sol’n

� Offers an explanation of why acids and bases neutralize each other (H+ + OH- = H2O)

� Restricts acids and bases to water sol’ns (similar reactions occur in the gas phase)

� Does not include certain compounds that have characteristics of bases (e.g., ammonia)

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� Brønsted acid: a hydrogen ion donor (H+, or proton)

� Brønsted base: a hydrogen ion acceptor

� Defines acids and bases independently of how they behave in water

� Amphiprotic: having the property of behaving as an acid and a base◦ Also called amphoteric, e.g., water

� Strong◦ Any acid that ionizes COMPLETELY in aqueous sol’n◦ Any base that dissociates COMPLETELY in aqueous

sol’n

� Weak◦ Any acid that PARTIALLY ionizes in aqueous so◦ Any base that PARTIALLY dissociates in aqueous

sol’n

� The rxn between Brønsted-Lowry acids and bases can proceed in the reverse direction (reversible reactions)

HX (aq) + H2O (l) ↔ H3O+ (aq) + X- (aq)

� The water molecule becomes a hydronium ion (H3O+),

and is an acid because it donated an H+

� H2O is the base because it accepted the proton (H+)

� The acid HX, after donating the H+, becomes a base X-

acid base conj. acid conj. base

� Conjugate Acid: species produced when a base accepts a hydrogen ion from an acid

� Conjugate Base: species produced when an acid donates a hydrogen ion to a base

� Conjugate Acid-Base Pair: two substances related to each other by the donating and accepting of a single hydrogen ion

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� Monoprotic acids: acids that contain only 1 hydrogen; e.g., HCl

� Diprotic acids: acids that contain 2 hydrogens; e.g. H2CO3

� Triprotic acids: acids that contain 3 hydrogens; e.g. H3PO4

� Having more than on e ionizable hydrogen does notnotnotnot mean stronger!

� Acid dissociation constant: (Ka): the equilibrium constant for the rxn of an aqueous weak acid and water

� Base dissociation constant: (Kb): the equilibrium constant for the rxn of an aqueous weak base w/ water

� Both are derived from the ratio of the concentration of the products and reactants at equilibrium

HA(aq) ↔ H3O+(aq) + A-(aq)

Ka = [H3O+] [A-]

[HA]

� Ka is a measure of the strength of an acid

� Ka values for weak acids are always less than one

� Used mostly w/ weak acids because the Ka

values for strong acids approach infinity

� HMnO4 (aq) + H2O (l) ↔

� H2S (aq) + H2O (l) ↔

MnO4-(aq) + H3O

+ (aq)

S-(aq) + 2H3O+ (aq)2

Ka = [MnO4-][H3O

+][HMnO4]

Ka = [S-][H3O+]

[H2S]

Kb = [HB+] [OH-][B]

� Kb is a measure of the strength of a base

� Kb values for weak bases are always less than 1

� Kb values for strong bases approach infinity

B(aq) + H2O (l) ↔ OH- (aq) + HB+(aq)

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� H2NOH (aq) + H2O (l) ↔

� NH3 (aq) + H2O (l) ↔

OH-(aq) + H3NOH+ (aq)

Kb = [H3NOH+][OH-][H2NOH]

OH-(aq) + NH4+ (aq)

Kb = [OH-][NH4+]

[NH3]

� pH: number that is derived from the concentration of hydronium ions ([H3O

+]) in sol’n◦ pH = -log [H3O

+]◦ As pH increases, [H3O

+] decreases

� Scale ranges from 0 – 14◦ pH = 7 is neutral [H+] = [OH-]◦ pH < 7 is acidic [H+] > [OH-]◦ pH > 7 is basic [H+] < [OH-]

Keep in mind that:Acids: high [H+] = low pHBases: low [H+] = high pH

� pOH = - log [OH-]

� pH + pOH = 14.00

� Calculating ion concentrations from pH

� [H+] = antilog (-pH)

� [OH-] = antilog (-pOH)

� Water can dissociate into its component ions, H+ and OH-

◦ 2H2O (l) ↔ H3O+ (aq) + OH- (aq)

� One water molecule acts as a weak acid, and the other acts as a weak base

� The ions are present in such small amounts they can’t be detected by a conductivity apparatus

� In pure water,

[H3O+] =1.0 x 10 –7 M

[OH-] =1.0 x 10-7 M

� It is defined as Kw: the ion product constant for water

◦ Kw = [H3O+] [OH-]

◦ Kw = (1.0 x 10-7)(1.0 x 10-7)

◦ Kw = [H3O+][OH-] = 1.0 x 1014

� The value of Kw can always be used to find the concentration of either H3O

+

or OH- given the concentration of the other

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What is the pH of a 0.001 M sol’n of HCl, a strong acid?

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What is the pH of a sol’n if [H3O+] = 3.4 x 10-5 M?

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The pH of a sol’n is measured with a pH meter and determined to be 9.00. What is the [H3O

+]?

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The pH of a sol’n is measured with a pH meter and determined to be 7.52. What is [H3O

+]?

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� In these problems, remember that the concentration of the [H3O

+] ions will equal the concentration of the conjugate base ions.

◦ This is because for every molecule of weak acid that dissociates, there will be an equal number of H3O

+

ions and base ions

Assume that enough lactic acid is dissolved in sour milk to give a solution concentration of 0.100 M lactic acid. A pH meter shows that the pH of the sour milk is 2.43. Calculate Ka

for the lactic acid equilibrium system.

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� An analytical method in which a standard solution is used to determine the concentration of another solution.

� In a titration, an indicator is used to determine the end point

� Standard sol’n: a sol’n of precisely known concentration

� Indicator: any substance in sol’n that changes color as it reacts with either an acid or a base

� Each indicator changes its color over a particular range of pH values (transition interval)

� An unknown acid sol’n will be titrated with a standard sol’n that is a strong base

� An unknown base sol’n will be titrated with a standard sol’n that is a strong acid

� Equivalence point: point at which the concentration of H3O

+ ions is the same as the concentration of OH- ions; [H3O

+ ] = [OH-]

� Endpoint: the point at which the indicator changes color

� Titration curve: graph that shows how pH changes in a titration

� The equivalence point is at the center of the steep, vertical region of the titration curve

� At the equivalence point, pH increases greatly w/ only a few drops

What is the molarity of a CsOH solution if 20.0 mL of the solution is neutralized by 26.4 mL of 0.250M HBr solution?

HBr + CsOH → H2O + CsBr

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What is the molarity of a nitric acid solution if 43.33 mL 0.200M KOH solution is needed to neutralize 20.00 mL of unknown solution?

What is the concentration of a household ammonia cleaning solution (NH4OH) if 49.90 mL of 0.5900M H2SO4 is required to neutralize 25.00 mL solution?