Chemistry 12 - Acids and Bases Part 2
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51 Terms
When a salt dissolves in water,…
the dissociated ions may hydrolyze to create a solution that is acidic or basic
hydrolyze definition
react with water
salt ionization in water
100%
if neither ion in a salt can undergo hydrolysis then…
the resulting solution will remain neutral
spectator ions
ions that do not undergo hydrolysis reactions
hydrolysis rule #1 (amphiprotic)
amphiprotic substances undergo both hydrolysis reaction
hydrolysis rule #2 (cations)
cations undergo hydrolysis except those belonging to group 1 and 2
hydrolysis rule #3 (anions)
anions undergo hydrolysis except those that are conjugates bases of strong acids
“p”
percentage dissociation
p formula
part over whole times 100
assumption to disregard X in calculations is justified if the…
percentage dissociation is less than 5%
H2CO3 and H2SO3 are examples of…
acids that do not exist
titration
a quantitative analysis technique in which measure amounts of solution are reacted with a know volume of another solution until an equivalence point is reached
equivalence point
the point in a titration where the stoichiometry of the reaction is satisfied; the mole ratio indicated by the balanced chemical equation has been met
titration reactions go to…
completion; equilibria does not form
what occurs at the equivalence point?
an abrupt pH change
indicators should be chosen so that they change colour very close to the….
equivalence point of the titration
tirant
chemical reagent of known molarity
analyte (aka titrand)
chemical reagent of unknown molarity
standard solutions
solutions of accurately known concentrations
a primary standard solution is typically prepared by…
measuring the mass of a solute and diluting it up to the calibration mark of a volumetric flask
a primary standard does not absorb…
carbon dioxide or moisture from the air
a primary standard does not absorb moisture which mean it is…
non-hygroscopic
upon heating in a drying oven, a primary standard must be…
chemically stable
a primary standard is obtained in…
pure form and dissolves completely
a primary standard has an accurately known…
molar mass
a primary standard reacts…
quickly and completely with the sample
metal hydroxide compound are unsuitable to act as a primary standards since they are…
highly hygroscopic
typical solid weak acids used as a primary standard
benzoic acid, oxalic acid dihydrate, and potassium hydrogen phthalate
secondary standard
substance thats concentration is calculated by titrating the primary standard against its solution
typical basic primary standard
sodium carbonate
when the equivalence point is reached during titration, the pH does not necessarily equal…
7 due to the produced salt hydrolyzing
the pH at the equivalence point depends upon the
relative strength of the reacting acids and bases
equivalence point pH of strong acid and strong base
equal to 7
equivalence point pH of weak acid and strong base
more than 7
equivalence point pH of strong acid and weak base
less than 7
weak acids and weak bases cannot be effectively titrated because they…
form equilibriums
acid-base indicator definition
weak organic acids or bases that change colour in solution as the pH changes
molecular formulas of an indicator are usually…
complex; HIn
midpoint pH
the average of the pH range values
transition point
the point at which an indicator is half way through its colour change; number of molecules of HIn equals the number of molecules of In-
what will be seen at the transition point?
an intermediate colour
end point of the titration
when the reaction is complete and the indicator changes colour
chemists must choose an indicator that will produce an…
end point in a pH region that approximates the equivalence point of the pH
an indicator is at the midpoint of its colour change when…
pH = pKa of the indicator
the pKa of the chosen indicator should be close to the…
pH at the equivalence point
the best indicators have the equivalence point pH within their…
transition range
in highly acidic solutions, an indicator is in its…
conjugate acid form
in highly basic solution, an indicator is in its…
conjugate base form
the concentration of hydronium at which an indicator changes colour equals the…
value of Ka for the indicator
universal indicator
an indicator solution which changes colour several times over a range of pH values.