mcat chemistry chapter 10 acids and bases kaplan Flashcards

Terms Definitions
litmus paper turns red in ?
litmus paper turns blue in?
bases turn litmus paper?
arrhenius def of acid and baseacid is?base is?
acid prod H+base prod OH-
what is the shortcoming of arrhenius def?
only desc a and b in aq media, not in non aqueous
bronst lowry a and ba isb is?
acid donate h+bases accepts H+
t or fNH3 and CL- are bronst lowry bases but not arrhenius bases
t or fa bronsted lowry defin of an a or a b is limited to aq solutions
the ______________ defin of an a or a b is limited to aq solut
bronst lowry acid and b occur in pairs called?
conjugate a b pairs
bronst lowry 2 members of a conj pair are related by a transf of?
a proton
H3O+ is the conjugate acid of the base?
NO2 - is the conjugate b of ?
lewis def of a and bacidbase?
acid is electr pair acceptbase is electr pair donator.
AlCl3 is a _______________ acid but not a ________________ acid
lewis but not a bronst lowry
AlCl3 can accept a?
electron pair
name of an acid is related to its?
parent anion
anion ending in -ide will become ______________ acid
hydro ic
flouride bec acid?
hydrofluoric acid
bromide becomes ________________ acid
hydrobromic acid
HF is?
hydrofluoric acid
HBr is ?
hydrobromic acid
hydrofluoric acid is?
MnO4- is what anion?
permanganate, even though there are no manganate or manganite ions
acids from oxyanions are called?
anion ends in ite it will be __________ acid
ous acid
anion ends in ate, it will be ____________ acid
ic acid
hypochlorous acid
chorous acid
chlorous acid
chloric acid
perchloric acid
nitrous acid
nitric acid
nitric acid
pOH is=
-log[OH-]= log (1/[OH-])
in any aq solut the H2O does what?
dissociates slightly
Kw is the?
water dissociation constant
Kw= [H+][OH-]=
ph + pOH=?
math reminderlog(xy)=?
logx + logy
pure water _____________ is equal to ________________
H+ is equal to OH-
pH below 7 is
pH above 7 indicates an excess of?
OH- ions
how can you estimate a logn x 10-m =
log(n x 10-m)= -m + logn the negative log ism-logn
m-lognsince n is a number betw 1 and 10 its log will be a fractoin betw ?
0 and 1
m-lognsince n will be a number betw 0 and 1.m-logn will be between m-1 and ?
m-lognthe larger n is the larger ?
the fraction logn will be the answer will be closer to m-1
If Ka = 1 .8 x 10-5, then pKa = estimate please
5 - log 1.8. Since 1 .8 is small,its log will be small, and the answer will be closer to 5 thanto 4. (The actual answer is 4.74.)
strong acids and bases are those that?
completely dissociate into their component ions in aq solution
when NaOH dissoc in water, why can you normally ignore the contribution of OH- from H2O?
as long as the amount of OH- or H+ is greater than 10-7 then you can ignore contribution of water.
when cant you ignore the contrib of water to acid and base calculations?
when it is a very weak acid or base whose H+ or OH- concentr is close to 10-7
1 x 10-8 M HCL solutionKw=(x+ 1 xlO-8)(x)=1.O x 1O-14 molecules).what is X?
where x=[H+]=[OH-] (bothfromthe dissociation of water
1 x 10-8 M HCL solution.Kw=(x+ 1 x lO-8)(x)=1.O x 1O-14 molecules).when do use this kind of equation. ?
when you have to calcul the H+ concentr with a weak acid. you could also use the equation for a weak base
name some strong acids
HClO4- perchloric acidHNO3 nitric acidH2SO4 sulfuric acidHCl hydrochloric acid
sulfuric acid is?
HCl is?
hydrochloric acid
HNO3 is?
nitric acid
name some strong bases
NaOH sodium hydroxideKOH potassium hydroxideother soluble hydroxides of gr IA and IIA metals
weak acids and bases only partly?
dissociate in aq sol
Ka measures?
the degree to which an a dissoc
the degree to which an an a dissoc is measur by?
the acid dissoc const Ka
t or fKa=[H3O][A-]/[HA]
Note that as a weak acid orbase, the effect on pH willalways be _______________ of astrong acid or base of the sameconcentration.
less than that
weaker the acid, the smaller the?
the weaker the acid, the _____________ the Ka
Kb is the
base dissociation constant
the weaker the base the ____________ the Kb
a conjugate base is formed when?
an a loses a proton
HCO3-/CO3- which is the conjugate a and b?
conjugate a HCO3-conjugate b CO3-
To find the Ka of the conjugate acid HC03, the reaction with __________must be considered.
HC03- (aq) + H20 (I) ---> H3O+ (aq) + C03 2- (aq)this reaction is used to calculate the ?
Ka of HCO3-
Ka X Kb=Kw=l x10-14this is for an acid and its?
conjugate base
what can we calculate for an acid and its conjugate base?
Ka X Kb=Kw=l x10-14
Ka and Kb are _____________ related
Ka and _______ are inversely related
if Ka is large then Kb?
will be small
if the conjugate a is strong then the conjugate base?
will be weak
to calculate the concentration of H+ in a 2.0 M aq sol of acetic acid CH3COOH (Ka=1.8 X 10-5) what should you do first?
write the equilibrium reaction
CH3COOH (Ka=1.8 X 10-5)write the equilibrium react
CH3COOH (aq)---> H+ (aq) + CH3COO- (aq)
to calculate the concentration of H+ in a 2.0 M aq sol of acetic acid CH3COOH (Ka=1.8 X 10-5) what do you do after writing the equil react?
write the express for the acid dissoc const
to calculate the concentration of H+ in a 2.0 M aq sol of acetic acid CH3COOH (Ka=1.8 X 10-5) write the acid dissoc const?
Ka=[H+][CH3COO-] ------------ = 1.8 X 10-5 [CH3COOH]
to calculate the concentration of H+ in a 2.0 M aq sol of acetic acid CH3COOH (Ka=1.8 X 10-5) what is the concentr of acetic acid at equil equal to?
its initial concentr 2.0 M- X, the amount dissociated
to calculate the concentration of H+ in a 2.0 M aq sol of acetic acid CH3COOH (Ka=1.8 X 10-5) [H+] is=?
to calculate the concentration of H+ in a 2.0 M aq sol of acetic acid CH3COOH (Ka=1.8 X 10-5) How can you rewrite the Ka expression?
Ka= [X][X]/[2.0-X]=1.8 X 10-5
to calculate the concentration of H+ in a 2.0 M aq sol of acetic acid CH3COOH (Ka=1.8 X 10-5) what can you approximate?
that 2.0-x is approx 2.0 bec acetic acid is a weak acid
Ka= [X][X]/[2.0]=1.8 X 10-5what did you approximate?
that 2.0-x is approx = to 2.0
Ka= [X][X]/[2.0-X]=1.8 X 10-5if when you solve for X it is close the the original concentr of acetic acid (2.0 M) what do you need to do?
you cant approx that 2.0-x is =2.0instead you have to use the quadratic equation
a neutrialization react is when?
an a and a base reat w each other, forming a salt and usually water
equation for neutralization
HA + BOH ---> BA + H2O
HA + BOH ---> BA + H2Othis is the equatrion for?
t or fneutralization reactions usually go to completion
salt ions reacting with water to give back the acid or base is ?
hydrolysis (in terms of a and b) is?
reverse react of neutralization, when salt ions react w water to give back the a or b
what combinations of a and b are possible?
1. str a and str b2. str a and weak b3. weak a and str b4. weak a and weak b
this is an ex of?HClO + NaOH ---> NaClO + H2O
weak acid w a str base
prod of a react betw equal concentr of a str acid and str base are?
salt and water, a and b neutr each oth so ph is 7
prod of a react betw str a and weak b are?
SALT, but usually no water is formed bec weak b are usually not hydroxides
weak bases are usually not?
str a w a weak bthe cation of the salt formed will do what?
will react w the water solvent, reforming the weak b
what are the react for HCL reacting with NH3?
HCl (aq) + NH3 (aq) --> NH4+ (aq) + Cl-(aq) Reaction INH4+ (aq) + H20 (aq) --> NH3 (aq) + H3O+(aq) Reaction II
str acid with a weak base the resulting solut will be?
weak a with a str b the resulting solut is?
weak a with a str b why is the result solut basic?
bec of hydrolysis of the salt to reform the aci and format of OH- from hydrolyzed water molecules.
ph of a weak a and a weak b depends on?
relative strenght of the reactants
the acid HClO has a Ka = 3.2 X 10-8,and the base NH3 has a Kb = 1.8 x 1O-5. what will the resulting solut be? acidic, basic, or neutral?
an aqueous solution of HCIOand NH3 is basic since Ka for HCIO is less than Kb for NH3
an a equiv is equal to ?
one mole of H+
a b equiv is equal to?
one mole of OH- ions
H2SO4 is a. monoproticb. diproticc. triprotic
b. diprotic
H2S04(aq) --> H+(aq) + HS04(aq)HS04(aq) --> H+(aq) + S042-(aq)what is this reaction showing?
that H2SO4 is diprotic
what is the equation for the dissoc of H2SO4?
H2S04(aq) --> H+(aq) + HS04(aq)HS04(aq) --> H+(aq) + S042-(aq)
one mole of H2SO4 can prod ______ acid equiv
2M H3PO4 would have be _________ N
how do you calcul equival weight?
divide the gram molecular weight by how many moles of H+ it liberates
what is equival weight of H2SO4?
98 g/mol is molec weightsince each mole liberates 2 acid equiv, the gram equiv of H2SO4 is 98/2 or 49 g.
name 3 polyvalent acids?
amphoteric means?
can act as an acid or a base
a substance that can act as an a or a b is?
bronsted lowryan amphoteric species can?
gain or lose a proton
t or fwater is amphoteric
the partially dissoc conjug base of a polyprotic acid is?
usually amphoteric
the hydroxides of Al, Zn, Pb, and Cr are?
the hydroxides of which metals are usually amphoteric?
Al, Zn, Pb, and Cr
t or fspecies that can act as either oxidiz or reducing agents are considered to be?
t or fspec that can act as red or oxidiz agents are consid to be amphoteric
oxid or reduc agents act amphoteric when they ?
accept or donate electr pairs, acting like Lewis a or bases
titration is used to ?
determ the molarit of an a or a b
in titrationyou react a ______ volume of a solution of unknown concentrat with a _______ volume of a sol of known concentrat
known volknown vol o
equival point is when the?
number of acid equival equals the number of base equival
t or fthe equival point is always at ph of 7
fonly for str a with a str base
when titrating polyprotic a or b there are several?
equivalence points
you estimate the equival point in titrat by what 2 methods?
1. graphical method- use ph meter2. watching for a color ch
indicators are?
weak organic a or bases that have differ colors in their undissoc or dissoc states
why dont indicators change the equival point
bec they are in low concetr
point at which the indicat ch color is called the?
end point
the _______ of the indicator and the __________ of the a and b should be close.
end pointequivalence point
what formula do yo use to calculate the volume added to reach the endpoint?
accord to this graph, has the best indicator been chosen?
no, bec the end point has a pretty different ph than the equival point of the titration
in the early part of the curve, the __________ species
acidic species
in the early part of the curve, the acidic spec dominates so small amounts of base will do what to the ph?
it will only change the ph a little
the addit of base most ch the concentr of H+ and OH- where on the graph?
near the equivalence point. this is where the ph the most
this is a titration of a ____________ with a strong base
weak acid
t or fthe titration of any monoprotic a with a str b will give a similar curve to this
the equival point is in the _______ range
a buffer consists of a weak acid or a weak base and?
its salt
give 2 examples of buffers?
examples of buffers are: a solution of acetic acid (CH3COOH) and its salt,sodium acetate (CH3COO-Na+); and a solution of ammonia (NH3) and itssalt, ammonium chloride (NH4+Cl-).
why are buffers useful?
Buffer solutions have the usefulproperty of resisting changes in pH when small amounts of acid or baseare added.
Consider a buffer solution of acetic acid and sodium acetate:CH3COOH <---> H+ + CH3COO-what happens when NaOH is added to the buffer?
When a small amount of NaOH is added to the buffer, the OH- ionsfrom the NaOH react with the H+ ions present in the solution; subse-quently, more acetic acid dissociates (equilibrium shifts to the right),restoring the [H+]. Thus, an increase in [OH-] does not appreciablychange pH.
Consider a buffer solution of acetic acid and sodium acetate:what happens when a small amount of HCl is added?
H+ ions from the HCl react with the acetate ions to form acetic acid. Thus[H+] is kept relatively constant and the pH of the solution is relativelyunchanged.
the henderson-Hasselbalch equation is used for?
The Henderson-Hasselbaich equation is used to estimate the pH ota solution in the buffer region where the concentrations of the speciesand its conjugate are present in approximately equal concentrations.
Henderson- Hasselbach equation is?
pH = PKa + log [conjugate base]/[weak acid]
henderson-hasselbachpH = PKa + log [conjugate base]/[weak acid]when the concentr of conj base equals the conc of the weak acid then?
ph=pKa, bec log1=0
henderson-hasselbachpH = PKa + log [conjugate base]/[weak acid]when will the concentr of conj base equals the conc of the weak acid ?
in a titration, half-way to the equivalent point
you can use the henderson-hasselbach equation to make a buffer at any?
pH. by carefully choosing a weak acid and its salt
this is titration of a __________ base with an acid
polyprotic base
This the the titration ofNa2CO3 with HCI in which the polyprotic acid is the ultimate prod-uct.
In region I, little acid has been added and the predominant species is
In region Il, more acid has been added and the predominantspecies are ______________, in relatively equal concentrations. The flatpart of the curve is the ______________, c
C032- and HC03,first buffer region
Region Ill contains the _______________ , at which all of the C032 istitrated to HC03. As the curve illustrates, a rapid change in pH occurs atthe ____________
equivalence point
Region Ill contains the equivalence point, at which all of the ?
C032 istitrated to HC03.
In region IV, the acid has neutralized approximately half of the HC03,and now _____________are in roughly equal concentrations.
H2C03 and HC03
In region IV the flatregion is the?
second buffer region of the titration curve.
In region V. theequivalence point for the entire titration is reached, as all of the HCO3-,is converted to?.
In region V. the___________________for the entire titration is reached, as all of the HCO3-,is converted to H2C03. Again, a rapid change in pH is observed near theequ
equivalence point
Blood pH is maintained in a relatively small range (slightlyabove 7) by a
bicarbonate buffersystem. This homeostasis can be upset, leading to a condition known as acidosis.
in a body you have the bicarbonate buffersystem. This homeostasis can be upset, leading to a condition known as ?.
What volume of a 3 M solution of NaOH is required to titrate 0.05 Lof a 4 M solution of HCl to the equivalence point?what equat should you use?
At equilibrium, a certain acid, HA, in solution yields 0.94 M [HA] and0.060 M [A-].Calculate Ka.
HA ---> H+ + A- The molar ratio of A- to H+ is 1:1, so [H+] must also be 0.060 M at equilibrium. It follows, then, that: Ka [A-][H+]/[HA] = (0.060)(0.060)/(0.94) = 3.8 X 10-3
13. Which of the following combinations would produce a buffer solutionof pH = 4? (Ka HN02=4.5 X 10-4)A. 0.30 M HNO2, 0.22 M NaNO28. 0.22 M HNO2, 0.30 M NaNO2C. 0.11 M HNO2, 0.50 M NaNO2D. 0.50 M HNO2, 0.11 M NaN
pH = PKa + log [A-/[HA]4 = 3.35 + log [A-]/[HA]0.65 = log [A-]/[HA][A-]/[HA] = 4.5 Only Choice C fulfills this criterion as 0.50/0.11 = 4.5.
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