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16 Cards in this Set
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Arrhenius Acid-Base definition -think most specific Bronsted-Lowery Acid Base Definition - think give/receive protons Lewis Acid-Base Definition - think electron movement |
Arrhenius Acid And bases -req. Aqueous solution Acid: will dissociate to form excess H+ in solution ex: H2O not considered an acid. H2SO4 is. Base: will dissociate to form excess OH- in solution Bronsted-Lowery Acid/Bases -Bronsted Acid: species donates H+ -Bronsted Base: accepts H+ ex: F- is a bronsted Base, but not an Arrhenius Base ex: H2O can act as congjugate acid or base Lewis Acid-bases Lewis Acid: Accepts electrons Lewis Base: electron Donor -also called covalent bond formation -complex ion formation nucleophile ( base: ) - electrophile (accepting e) interactions **an Arrhenius acid---> is a Bronsted Acid----> is a Lewis Acid... not in reverse |
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Define Amphoteric species - most common on MCAT? |
one that reacts like an acid in a basic environment, or acts like a base in an acidic environment ex: H2O is most common * or species that can act as both oxidizing/reducing agents are amphoteric -includes: accepting/donating electrons(Lewis acid-base) ex: amino acids, bicarbonate, bisulfate, metal oxides |
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Acid-Base Nomenclature levels of oxygen w/ names to: -Hypo -ite -ite -ate -Per -ate - ous: adding a hydrogen |
ClO- hyperchlorite HClO hypochlorous acid ClO2 - chlorite HClO2 Chlorous Acid ClO3 - Chlorate HClO3 Chloric Acid ClO4 - Perchlorate HClO4 Perchlorous Acid -ous if you add H to beginning hypo+ ite--> ite --> ate --> Per+ -ate when adding more oxygen |
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Acid-Base autioinization behavior of H2O -most acid base rxns are in water what is autoionization |
water- amphoteric - acts as acid in presence of a base - acts as a base in presence of an acid water+water (react on self) Auto ionization H2O(l) + H2O(l) <--> H3O+ (aq) + OH- (aq) -one molecule donates H to other->hydronium ion - result: OH- made and H+ (H3O+) |
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Equilibrium of H2O (Kw)- * what is the value of water dissociation constant? -hint: think pH + pOH= what number? What is Kw dependent on?( any equilibrium constant) w/ Le Chatelier's Principle: adding H+ or OH- - what direction will autoionization go? |
Pure water Kw= [H+][OH-]= 10^-14 @ 25C or 298K *one mole water will form 1 mole H+ and 1 mol OH- - Temperature dependent!!! *Le Chateliers - Add product: ex: H+ - rxn shifts towards reactants * will have a decrease in [OH] - Adding a species that accepts H+ species? *will have decrease in [H+] system shifts towards products to replace H+ ions
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pH and pOH Scale - concentrations are both equal to... hint: in exponents we use the -log to simplify the scale - the scale of pH is zero to ____ |
if Kw of H2O @ 298k = 10^-14 then [H+] and [OH-] are both = 10^-7 M each ---log scales simplify the concentrations--- scale is on a 0-14 instead of exponents--- pH= -log[H+] = log 1/[H+] pOH= -log[OH-] *@298k, both [H+] and [OH-] =10^-7M @298K pH=-log[10^-7]= 7 so pOH = 7 neutral solution pH+pOH=14 --math reminder: log( X Y) = log(X) + log(Y) |
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Estimating Scale Values ** convert pH, pOH to pKa and pKb vice versa |
if original value is a power of ten... very easy if [H+] = 0.001 or 10^-3 then pH=3 if pH+pOH=14, then pOH= 11 if Kb= 1.0x10^-12 then pKb=12 remember: log(1)=0 and log(10)=1 n is a number between 1 and 10 the log of #1-10 will be a a number between# 0-1 |
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Ka to pKA examples if Ka of acid= 1.8 x10^-5, what is pKa? |
break down the numbers -log( n x 10^-m ) = -log(n) - log(10^-m) so.. = m - log(n) n: # between 0 and 10 log(#0-10) will be a decimal between 0 and 1 use an estimate p value~ m- 0.n (move deci. one spot or divide by 10) ex: pKa= --log (1.8 x10^-5) = 5 - log(1.8) ~ 5 - 0.18 pKa~ 4.82 (actual 4.74) |
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strong acids and bases do they associate minimally or completely? What are some examples of strong acids and bases? |
Strong acids/bases dissociate completely in aqueous solutions ex: NaOH --> Na+ + OH- a 1M NaOH solution yield 1M Na+ and 1M OH-
calc pH= 14- pOH= 14- (-log[OH-] ) pH= 14 - (-log[1M] = 14-0= 14 * remember log(1)=0 and log(10)= 1 so -log(1)= 0 and -log(10) = -1 Strong Acids HCl HBr HI H2SO4 HNO3 HClO4 Strong Bases KOH |
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Weak Acids and Bases do they dissolve partially or completely to reach equilibrium state? is the Ka (equilibrium dissociation constant) higher or weaker for acids? what does the disccociation constant refer to? - think about how much/ how little acid dissociates in reference to its Ka |
weak dissociate Partially or incompletely ex: HA: only dissociates partially to achieve equilibrium
HA + H2O <--> H3O+ + A- @equilibrium: can calc. dissociation to determine the Ka- acid dissociation constant Ka= [H3O+][A-] / [HA] -products over reactants, no liquids or solid in Eq euqations Small Ka: WEAK ACID Ka< 1 - this means it will not dissociate fully - smaller the Ka, weaker the acid, less dissociation in aqueous solution |
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Weak Bases: - dissociate completely or incompletely? |
ex: BOH BOH <--> B+ + OH- can calculate dissociation constant Kb= [B+][OH-] / [BOH] Small Kb = WEAKER base Kb< 1 is extremely weak - smaller the Kb, weaker the base, less dissociation ***MCAT: molecular nonionic amines are almost exclusively weak bases |
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Conjugate acid-base pairs strong acid- high or low Ka? - conjugate base- high or low Kb? Strong base- high or low Kb? - conjugate acid- high or low Ka? |
refer to: Bronsted acid-base: proton transferred from an acid to a base - the donating and receiving are called conjugates Conjugate Acid: acid formed when a base gains H+ Conjugate base: formed when an acid loses a proton ex: HCO3- + H2O <--> CO3^2- + H3O+ * CO3^2- is conjugate base of HCO3- H3O+ is conjugate acid of water Ka= [CO3][H+] / [HCO3-] *reversible rxn w/ water CO3^2- + H2O <--> HCO3- + OH
Kb= [HCO3][OH-] / [CO3] *don't include pure liquids, solids |
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Conjugate acid-base pairs strong acid- high or low Ka? - - conjugate base- high or low Kb? Strong base- high or low Kb? - conjugate acid- high or low Ka? * will weak acids have a conjugate strong base? vise versa? |
Strong Acid: Ka will be high conjugate base Kb will be low Strong Base: Kb is high conjugate acid: low Ka weak acids/bases yield weak acids/bases |
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Induction: - w/ high Electronegative elements |
high EN elements near an acidic proton - increases acid strength - EN elements e- affinity pulls electrons away from proton - acidic proton: easily dissociates(more acidic) |
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Salt Formation - from acids and bases in neutralization rxns - do neutralization rxns go to completion? - what can we react w/ a salt to yield the acid or base?
what four scenarios of stron acid/bases will yield |
HA + BOH <--> BA +H2O * salt may precipitate or remain ionized - neutralization rxn goes to completion - Hydrolysis: salt reacts w/ water to give back the acid or base |
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Titration and Buffers
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Titration: used to determine concentration of a known reactant in a solution |
