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100 Cards in this Set
- Front
- Back
why are pH & acid base balance important
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[H+] in body is tightly regulated. Provides conditions for optimal intracellular function esp:
-intracellular trapping of metabolite intermediates is maximized at intracellular pH of neutrality; -activity of proteins (enzymes) is optimized b/c net charge kept constant |
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name the three definitions of acid & bases in aqueous solutions
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Arrhenius
Bronsted-Lowry Lewis |
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What is the Arrhenius definition of acid/base
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Arrhenius:
acid: H+ or H3O+ producer in water (HCl, HNO3) think Arr H enius = H+ or OH- base: OH- producer in water (NaOH, LiOH) |
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what is the Bronsted-Lowry definition of acid/base
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Bronsted-Lowry
Acid: proton (H+) donor Base: proton acceptor think brOnsted-lOwry = proton |
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what is the Lewis definition of acid base
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Lewis
acid: electron-pair acceptor base: electron pair donor think l E wis = electron |
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In the Bronsted-Lowry definition what do acids donate? what do bases accept
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acids donate protons
bases accept protons |
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an acid becomes a ____ after the donation of its proton
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base
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if acids or bases are 100% ionized in solution, they are said to be this
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strong acids or strong bases
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How do you recognize conjugate acid-base pairs
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conjugate acid base pairs differ by exactly 1 H ion;
the charge on the conjugate acid is always one greater than the charge on the conjugate base |
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according to the B/L theory, acids donate protons--otherwise known as
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H+
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according to the B/L theory, the solvent (eg H20) may act as a ___________ or ____ acceptor
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proton or H+
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an acid becomes a ____after the donation of its proton, since the process may be reversed
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base
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a base becomes an _______after accepting a proton or H+, since the process may be reversed
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acid
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In the equation:
HCl ---> H+ + Cl- HCl is an acid if HCl gave away its H+, that leaves Cl-, in the reverse direction, Cl- becomes the _____ base of HCl because it takes a H+; conversely HCl is the ________acid of Cl- |
conjugate; conjugate
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the higher the Ka (the equilibrium constant for dissociation of a weak acid), the __________the tendency to dissociate a proton
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greater
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H30+ is the __________ion
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hydronium
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the hydronium ion is
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H30+
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when you have an acid (Hx) and base (x-) that differ in the presence or absence of H+, they are called
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conjugate acid/base pairs
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every acid has a ______base formed by removing H+
(X- is the conjugate base of HX) |
conjugate
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every base has a _________acid by adding H+
(HX is the conjugate acid of X-) |
conjugate
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stronger the acid, the ______ the conjugate base
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weaker
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the stronger the base, the ______the conjugate acid
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weaker
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in the reaction,
HA + B ---> <--- A- + HB + which are the conjugate pairs & why |
the two pairs of protonated & deprotonated substances are HA & A-, and HB+ & B are called conjugate acid-base pairs
when an acid gives away a proton, it always gives it to a base, so when an acid gives away its H+ to a base, the acid is converted into its conjugate base |
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what is the definition of a strong acid
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a strong acid is a proton-donating compound which is completely dissociated in water to produce only H30+ (aq) ions & accompanying anions
eg: HCl, HNO3, H2SO4 |
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what is the definition of a strong base
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a strong base is a compound which is completely dissociated in water to produce only OH-(aq) & accompanying cations
eg: NaOH, Ca(OH)2, KOH |
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a hydroxyl ion is
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OH-
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a hydrogen ion is
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H+
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what is a neutralization reaction
HCl + NaOH ---> H20 + NaCl |
a neutralization reaction is a chemical reaction between an acid & base, that yields a salt & water
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a neutralization reaction is a chemical reaction between an acid & a base that yeilds a ____ & _____
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salt & water
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is this a strong or weak acid and why
HA + H20 ---> H20 + A- |
strong acid b/c complete dissociation
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partial dissociation means the acid is
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weak
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strong acids dissociate _____ into _____ in water
-----> |
completely, ions
100% ionized all starting reactants are converted into products |
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weak acids dissociate very _____ into ions in water
<----- ------> |
slightly
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the Hydronium ion
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H30+
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what is H30+
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the Hydronium ion
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the ____ of a solution is normally specified by the concentration of _____ in moles per liter of solution, M
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the ACIDITY of a solution is normally specified by the concentration of H30+ (hydronium ion) in moles per Liter of solution, M
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strong acids: acid concentration =
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[H30+]
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weak acids: acid concentration >
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[H3O+}
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Pure water has a [H30+] =
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1 x 10 -7 M
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1 x 10 -7 M is what
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concentration of H30+ in pure water
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[ ] or brackets mean what
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molar concentration
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concentrations of species in acid-base chemistry are always expressed as
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molaRity
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sulfuric acid: H2SO4
Hydroiodic acid: HI Hydrobromic acid: HBr Hydrochloric acid: HCl Nitric acid: HNO3 are all examples of _____acids |
strong acids
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Lithium hydroxide: LiOH
Sodium hydroxide: NaOH Potassium hydroxide: KOH Barium hydroxide: Ba(OH)2 are examples of strong ___ |
bases
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water as an acid & base
H20 + H20 <-->H30+ + OH- Ka= |
Ka = [H30+][OH-] / [H20][H20]
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the relative strength of a weak acid is quantified by the equilibrium constant,
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Ka
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Ka is the
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equilibrium constant that indicates the relative strength of a weak acid
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a large Ka means a ____ acid
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stronger
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of the following acids, which is the strongest based on Ka
H3PO4 (phosphoric acid) Ka= 7.1 x 10 -3 versus NH4+ (ammonium ion) Ka=5.6 x 10 -10 |
Phosphoric acid is stronger based on Ka (because 10 -3 is larger than 10 -10)
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Kw is the
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ion-product for water
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the ion-product of water is
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Kw
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PKw =
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PKw = -logKw
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what scale is used to express H+ ion concentration in water
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the pH scale
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pH of neutral soution =
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pH =7
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pH of acidic solution <
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7
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pH of basic solution >
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7
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express pH of an acidic solution <7 according to hydronium versus hydroxide ions
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[H30+] > [OH-]
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express pH of a neutral solution =7.00 in terms of hydronium & hydroxide ions
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pH =7
[H30+] = [OH-] |
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express pH of a basic solution > 7 in terms of [H30+] & [OH-]
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pH > 7 is basic
[H30+] < [OH-] |
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pH =
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- log[H30+]
pH = - log[H30+] |
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- log[H30+] is
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pH = - log[H30+]
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pH is a________-scale. One pH unit of change means the hydrogen ion concentration changes _____ fold
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pH is a logarithmic scale, therefore one pH unit of change means the H+ concentration changes 10 fold
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these acids have more than one Hydrogen & can ionize more than once
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polyprotic acids
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biologically, the MOST important polyprotic acid is
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carbonic acid, H2CO3
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H2CO3 is
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carbonic acid= H2CO3
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H2CO3 <-->
& HCO3 <---> |
H2CO3 <--> H+ + HCO3-
& HCO3 <---> H+ + CO3 -2 |
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polyprotic acids can neutralize as many ____ ions as they have _____
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OH- ions as they have H+
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carbonic acid (H2CO3) & sulfuric acid (H2SO4) can neutralize ____ OH- ions
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2
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phosphoric acid (H3PO4) can neutralize ___ OH- ions
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3
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what is a buffer solution
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a buffer solution is one that maintains a constant pH in spite of addition of a lot of acid or base
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most buffers consist of a solution of a weak ___ and its ____
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acid & its salt
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what is the MOST IMPORTANT buffer in blood
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carbonic acid (H2CO3)
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the proton dissociation of an acid is characterized by an acid _______ & its ____
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the proton dissociation of an acid is characterized by an acid dissociation constant (Ka) & its pKa value
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pKa =
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pKa = - log10 (Ka)
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ionizable groups of ____ & _____ are critical for biological function
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Amino Acids & Proteins
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Protonated
express pH vs pKa |
Protonated
pH < pKa |
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Deprotonated
express in terms of pH & pKa |
deprotonated
pH > pKa |
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the _____ equation calculates the ionic form of the molecule at a given pH from the pKa value of each acid group
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Henderson-Hasselbach
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in general, a weak acid dissociate to a limited extent in water to what
HA --> <-- H+ + A- |
the hydronium ion & conjugate base
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the tendency of the acid (HA) to dissociate & donate a H+ is the
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Ka, the equilibrium constant for dissociation
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pKa =
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pKa = - logKa
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-logKa is the
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pKa
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the higher the Ka, the ____the tendency to dissociate ( ie the stronger the acid)
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greater
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the higher the Ka, the ____ the acid
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stronger
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H-H equation
the pH of solution of weak acid *Dissociation constant = Ka = [H+]{A-]/ [HA] isolate for H+ |
[H+] = Ka *[HA]/[A-]
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lactic acid is a weak acid which means it __________dissociates in water
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only partially dissociates
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lactic acid dissociates in water resulting in ____ & ___
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lactate ion & H+
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pKa is the PH at which ___% of the acid is dissociated
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50%
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in the ___ form the substances are able to pass through the lipid membranes
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undissociated
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the dissociated (ionized) form of substrates (are/are not) able to pass through the lipid membrane
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are not
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the carbonic-acid-bicarbonate buffer in the blood
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CO2 + H20
carbonic anhydrase H2CO3 (carbonic acid) ^ v HCO3- + H+ (bicarbonate) |
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carbonic-acid bicarbonate buffer
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pH = pK -log [ [CO2]/[HCO3-] ]
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if the pH < pKa then [HA]
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if the pH < pKa, then
[HA] >> [A-] + [H+] weak acids barely dissociate |
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if pH > pKa then [HA]
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if pH > pKa then
[HA] <<< [A-] + [H+] weak acids will be majority dissociated |
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the pH of the drug solution will depend upon the
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pKa
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buffers do this to pH
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stabalize
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phenobarbitol pKa
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pKa 7.4
Phenobarbitol |
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given the H-H equation the
pH = |
pH = pKa + log [ionized] / [nonionized]
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all processes are at some ____; if you change the concentration/temperature/reactants/products, you will try to reach a new _____
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equilibrium; equilibrium
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pH of drug solution is dependent on the ___of a compound
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pKa
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