Acid and Base Review Flashcards
whats the end point
the point where the sample chemical has all been reacted and the titrant is now reacting with the indication causing a colour change
whats the titrant
the reagent/solution in the burette that is added to the contents of the flask
steps for weak acid calculation type 2
- write the BL reaction equation for the substance n the question with water
- make an ICE table
- use the pH given to get the H3O concentration and then fill in the missing values in the table
- use the equilibrium concentrations to solve for Ka
whats the equation for the major intracellular buffer system in the cell plasma***
H2PO4-(aq) <–> HPO42-(aq)
how do you know what form an indicator is in
if the indicator contains H, its in an acid form; if the indicator is just its symbol with no H its in its base form
where will the equivalence point be if a weak base is titrated
below 7
how do you predict the equivalence point
pick out the steepest part of the curve and then determine the point that is in the middle of that section
can a buffer system have a strong species in it
no
when do buffers function best
when the pKa of the conjugate weak acid used is close to the desired working range of the buffer; the more equal amounts of conjugate pairs and the higher their concentration, the longer the buffer will last
whats pKa
measure of the acidity of a compound, specifically how easily a molecule donates a proton
what are polyprotic acids and bases
species that can accept or donate more than 1 hydrogen ion/proton
how do you recognize a polyprotic base
by the size of the negative charge (anything greater then 1- is polyprotic)
what does it mean if the titration curve starts with a pH between12-14
you are dealing with a strong base
what happens at the equivalence point of a titration curve
the acid and base have completely reacted to neutralize
what does it mean when the line on a titration curve starts at a pH between 0 and 2
that your starting with a strong acid
where does the sample go during a titration
In the flask on the counter thats underneath the little tube
approximation rule for acids and bases
if [initial acid]/Ka is >1000 then approximation rule applies
how do you determine whether it should be an acid or base calculation when dealing with an amphoteric/amphiprotic substance
compare the Ka and Kb for the substance and whichever is bigger determines the type of weak species calculation
where does the H2CO3(aq) in the blood buffering system come from
the lungs
what is the normal pH of blood plasma and how is this maintained
7.4; maintained by the intracellular buffer system in the cell plasma
where do you put the titrant during a titration
its held in the little tube at the top
whats a buffer
a solution that can resist pH change upon the addition of an acidic or basic components
what are the 6 rules regarding listing entites in a BL reaction
- ionic compounds dissociate into ions
- strong acids dissociate into ions
- strong bases dissociate into ions
- weak acids are left as is
- weak bases are left as is
- always add water
how do you recognize a polyprotic acid
any acid that contains more then 1 H
how do you know what percentage to put above the arrow in your final BL reaction when no strongs are present
> 50% when the strongest acid is higher on the table than the strongest base
<50% when the strongest acid is lower on the table than the strongest base
steps for weak acid calculation type 1
- write the BL reaction equation for the substance in the question with water
- mace an ICE table from the equation
- check to see if approximation rule applies
- use Ka expression to solve for the equilibrium concentrations
where will the equivalence point be when a strong acid and base are titrated
on or very close to 7.0 pH
what does it mean when a substance is amphoteric/amphiprotic
it can either donate or accept an H ion meaning that the substance can act as both an acid and a base
what does it mean when the line on a titration curve starts at a pH between 2-6.5
your dealing with a weak acid
whats a titratiom curve
a graph of changes in pH during a titration
can a buffer just be one chemical
no, it must consist of a weak conjugate acid-base pair
what does it mean if the titration curve starts with a pH between 12 and 7.5
you are dealing with a weak base
whats the Ka expression
Ka = [products]/[reactants]
what is a common biological buffer system*****
the carbonic acid and hydrogen carbonate ion conjugate acid base pair is the major buffering system in the blood and other body fluids
what is the major intracellular buffer in cell plasma***
the conjugate acid base pair dihydrogen phosphate and hydrogen phosphate ions
whats the equivalence point
the point where there has been enough moles of titrant added to be equal to the moles of sample content so that the reaction is complete and the sample has been neutralized
what does a buffer do/whats its purpose
it is able to neutralize small amounts of added acid or base, making the pH of the solution remain relatively stable
how do you calculate the pKa of a substance
pKa=−log(Ka)
what does the shape of a titration curve depend on
the strengths of the acids and bases used
why can a buffer resist pH change
because the two components (conjugate acid and conjugate base) are both present in appreciable amounts at equilibrium
what is the equation for the major buffering system in blood and other body fluids ***
H2Co3(aq) <–> HCO3-(aq)
how do you tell which number is bigger when dealing with numbers multiplied by 10 to the power of something
whichever exponent is lower is the bigger number
whats the sample
the reagent/solution that is put in the Erlenmeyer flask; the solution that is getting added to
what do all titrations require to be able to show a defined equivalence point
at least one strong species
where will the equivalence point be if a weak acid is titrated
above 7
5 steps for predicting brownsted lowry reactions
- list all entites
- labek all entities as WA, WB, SA, SB, or SI
- identify strongest acid and strongest base
- use those 2 to write a BL reaction
- chose arrow and add percenage
how do you determine the strongest indicators among other acids and bases
based on the Ka value of the indicator which you can use to help you fit the indicator into the table
whats the pH of water
7
what are indiators
weak acids that have a different colour than their conjugate base
how is the appropriate acid/base indicator for a titration chosen
based on its pH range or transition range
rules for picking your arrow at the end of making a BL reaction
if there are strongs present then use a one way completion arrow%; if there are no strongs present then use an equilibrium arrow
whats the Kb expression
Kb = Kw/Ka of conjugate acid
steps for weak base calculation
- write the BL equation
- make an ICE table from the equation
- convert Ka to Kb
- check for the approximation rule
- use a Kb expression to solve for the equilibrium concentrations
- convert to pH or any other needed values
