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28 Cards in this Set
- Front
- Back
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Arrhenius Acid
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First, most specific definition of an acid and base - Arrhenius Acid: will dissociate to form excess of H+ in solution *Limited to aqueous acids and bases - HCl, HNO3, H2SO4 |
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Arrhenius Base
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Arrhenius Bases will dissociate to form an excesds of OH- in solution *Limited to aqueous acids and Bases - Oh at end of formula NaOH, Ca(OH)2, F3(OH)3 ---relationship: every Arrhenius acid/base can be a Bronsted Lowery Acid/Base which can be Lewis Acid/Base --does not go the other way around |
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Bronsted Lowery Acids and Bases
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*Not limited to aqueous solutions like arrhenius Bronsted Base: accepts H+ ex: OH-, NH3, F- Bronsted Acid: Donates Hydrogen Ions Ex: H2O can donate H+ Same w/ Arrhenius: only an acid if it produces hydrogen ions,H+ *most equatons will involve transfer of a hydrogen ion in accordance with bronsted lowery definition |
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Conjugate Acid-Base Pairs
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acids and bases always occur in base pairs ex: autoionization of 2 H2O conjugate acid is H3O+ conjugate base is OH- |
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Lewis Acids and Bases think of an example of what is being donated and which receives... |
Most inclusive(includes all) definition Lewis Acid: Accepts electrons -------"Lewis Loves electrons" Lewis Base: electron Donor - lone pair can be donated Attack on the electrophile(acid) by the nucleophile(base) ex :NH3 donates(Lewis Base) his electrons to BF3(lewis acid) that accepts the electrons (also coordinate covalent bond) |
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Bronsted Lowery vs Lewis Acids/Bases
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Lewis Definition: focus is on movement of electrons Bronsted-Lowery: focus is on movement of Hydrogen Ion (H+), or a naked proton in rxn: lewis acid donates its H+ to a base(H+ acceptor) |
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Amphoteric Species
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Acts as an acid in a basic environment Acts like a base in an acidic environment w/ B-Lowery: amphoteric species can gain/lose a proton--> amphiprotic also: polyvalent acids ex: Bicarbonate, or HSO4- can gain/lose H+ -oxi/reduc agents also amphoteric -gain/lose e- ampho ex: H2O + B- <--> HB+ OH- (water acts as an acid- it protonates B-) ex: HA+ H2O<---> H3O+ + H- (Accepts the H+, a base) |
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Are Zwitterions amphoteric?
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Yes. Zwitterions: cationic and anionic character( NH3+ and COO-) -amino can release proton(acid) - COO- can accept a proton(base) |
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Acid Base Nomenclature of oxyanions and oxyacids |
Oxyanions become oxyacids (gaining Hydrogen) anion ends with ite(less oxygen)= acid end w/ -ous acid Anion w/ ate(more oxygen)= acid end w/ -ic acid Levels( less oxygen-->More) -Hypo-ic ---> -ite ---> ate ---> Per---ate ex: chlorate ClO3- |
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Acid/base Properties
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characterized according to their relative tendencies to donate or accept hydrogen ions *aqueous acid/base solutions can be characterized according to their [H+] and [OH] ions most acid base rxn take place in water |
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Acid-Base behavior of Water
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H2O is Amphoteric(acid in presence of base, base in presence of acid) water+water (react on self): autoionization H2O(l) + H2O(l) <-----> H3O+(aq) + OH-(aq) products: Hydronium Ion and Hydroxide Water disassociation Kw= [H3O+][OH-]=10^-14 @25C or 298k or in other words --- equal amounts of H+ and OH- in Kw pure water -if H+ Ions added to neutral solution: rxn will shift left to reach Kw, by removing[OH-] **In RXNs: use H+ instead of writing H3O+ - but a proton is never isolated in a solution- always attached to water or species that can accept it |
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Le Chateliers principle in acids and bases |
Adding a product will shift rxn to reacents side•Adding H+ to neutral solution@Kw •[OH-] will reduce to compensate, make H2O removing a product will shift rxn to product side•adding a hydrogen accepting species•reduces [H+], rxn shifts to replace [H=] |
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Equilibrium Constants are only dependent on _____________. what is the Kw of H2O @298k? |
Temperature only variable that affect equilibrium constants w/ Kw @298k, always = 10^-14 >298K, Kw INC(H2O is endothermic) |
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Concentration Scale of acid and basic solutions can be condensed into manageable numbers using ____________ scales.. using __ and ___. what are the equations for measuring both? The concentrations of [H+] and [OH-] in neutral H2O can be translated to their __ and __ (#s) |
using Log scales to form pH and pOH for the [H+] and [OH-] pH= -log(H+) or ph= log( 1/[H+] ) pOH= -log(OH-) or pOH= log (1/[OH-]) Neutral H2O: pH=7--> -log10^-7 pOH=7---> -log10^-7 **if pH increases, then pOH decreases pH+pOH=14 ----> b/c log product equal to sum logs or.... log(XY)= LogX+ LogY low pH=more acidic |
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Convert [H+] to pH....deduce the pOH (from 14) if [H+]= 0.003M |
0.001 is 10^-3, then the pH is 3. 14-3=9=pOH
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Using Log Shortcut to get an approx. on P Scale Knowing that n x 10^-m where n= 0 to 10) |
taking the negative log -log(n x 10^-m)= -log (n) - log(10^-m) = m- log(n) n: number between 0 and 10. n=1 log(1)=0 will be a decimal n=10;log(10)= 1 Better way: p value is estimated using: pka=m-0.n <-- slide decimal left by 1 ex: if Ka of acid=1.8x 10^-5, what's pkA? pKA= 5 - log(1.8)= 5-0.18 = 4.82 (actual 4.72) |
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Strong Acid and Bases Relate Molar ratios to reactants and products |
completely dissociate into their component ions in aqueous solution Ex: NaOH----> Na+ + OH- (OH-) is strong base -- if 1MNaOH, then yield 1M Na and 1M OH- *assume autoionization H2O negligible b/c in presence of strong base -only if around 10^-7M |
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Weak Acids and Bases Properties
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only partially dissociate in aqueous solutions acid dissociation constant (Ka)= [H3O+][A-]/ [HA] smaller Ka= weaker acid - less dissociation(Ka<1) ------no liquids, solids in Eq equations----- base dissociation constant(Kb)= [B+][OH-]/ [BOH] smaller Kb=weaker base Ka<1 (less dissociation) *** weak acid if Ka<1 and weak base if Kb<1 --- weak bases nonionic almost exclusively amines on MCAT |
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Conjugate Acids and Bases
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In bronsted-Lowery acid base reaction: Hydrogen Ion(proton) transferred from an acid to a base Conjugate acid: base gains H+ Conjugate Base: Acid loses H+ ex: HCO3- +H2O <---> CO3^2- +H3O+ CO3^2- is conjugate base and H3O+ is conj. acid water is a weak acid and a weak base |
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Equilibrium constant of water is equal to what plus what?
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Kw= Ka+Kb Ka,acid+ Kb, conjugate base=10^-14=kw Kb,base +Ka,conjugate acid= 10^-14=kw If Ka increases, kb has to decrease |
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Induction from an electronegative element is
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high EN elements near an acidic proton increase acid strength by pulling electron density out of bond holding the acidic proton --weakens proton bonding and facilitates dissociation keypoint: acids with EN elements nearer to acidic hydrogens are stronger than those that do not. |
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Calculate the concentration of conjugate acid in 2M solution of [reactant] an aqueous formula (Ka= 1.8x10^-5) Ka= [conj acid][conj base] / [reactant]=1.8x10^-5 |
Ka= [x][x]/ [given concentration, 2M]=1.8x10^-5x^2= 1.8x10^-5 x 2M ---> x^2= 3.6x10^-5 ** if square root, half the exponent 3.6x10^-5----> 36x10^-6=x^2x=6x10^-3M
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Neutralization Reaction: Acid + Base forms ___
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Acid+ Base to form a salt and sometimes water HA+ BOH ---> BA +H2O |
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Normality: Acid and base equivalents proportions
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acid equivalent: equal to one mole of H+ (or H3O+) base equivalent: equal to one mole of OH- polyprotic: one mole of acid or base liberates more than one acid or base equivalent ex: H2SO4 +H2O ---> H3O+ + HSO4-not@Eq HSO4- +H2O <---> H3O+ + SO42- @Eq 1M H2SO4 yields 2M H3O+ common polyvalent acids H2SO4 H3PO4 H2CO3 common polyvalent bases Al(OH)3 Ca(OH)2 and Mg(OH)2 |
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Gram equivalence weight also good measure for acid base chemistry |
GEW: mass of a compound that produces one equivalent (one mole of charge) ex: H2SO4 (mm 98g) is divalent; 2 equivalents so 98/2 48g--- the gram equivalence weight for H2SO4 so dissociation of 48g of H2SO4 will yield 1 acid equivalent (one mole of H3O+) |
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Define Titration - Titrant -Titrand |
Titration: determine concentration of a known reactant in a solution ( acid-base, redox,) Titrations: adding small volume of titrant:a solution w/ known concentration to Titrand: solution w/ known volume but unknown concentration |
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Acid-base Equivalence Points Equation w/ equivalents? |
Equiv. Point@ #acid equivalents= # base equivalents (strong acid and base will be @pH7) w/ polyprotic acids/bases - will have multiple equiv. points as conjugate species is titrated separately # equivalents acid/base can be found with known volumes N1x V1= N2x V2 |
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Describe an acid-Base titration Indicator
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weak organic acids/bases w/ diff colors in protonated and unprotonated states -low [c] will not affect equivalence point must be a weaker acid/base than acid/base being titrated (or indicator would get titrated fi |
