Triangle inequality proof complex

IN
-
DEPTH ONLINE LAB INVESTIGATION
:
ACID
-
BASE TITRATIONS
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Can you......
□
give the Arrhenius and Brønsted
–
Lowry definitions for acids and bases?
□
remember acid
-
base nomenclature?
□
describe reactions of acids and bases in aqueous solutions?
□
calculate and explain the concept of pH?
□
describe the dissociation processes that occur in aqueous solutions for
acids and bases (strong and weak)?
□
write a complete balanced equation, ionic equati
on, and net ionic equation
for a chemical reaction that occurs in aqueous solution?
□
use a scientific/graphing calculator to perform calculations involving
logarithms?
□
interpret graphical representations of data?
What is a titration?
What purpose does it
serve?
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BACKGROUND
READING.....
Titrations
Suppose that you were to dispense 0.500 M sodium hydroxide (NaOH) from a buret into an
Erlenmeyer flask containing 50.0 mL of hydrochloric acid (HCl). Not only would a neutralization
reaction occur, but careful measurements would enab
le you to determine the concentration of the HCl
solution. Such an analysis, termed a
titration
, is used to determine the unknown concentration of an
acid or base by reacting it with a known concentration of acid or base.
During the titration process, as
the acid and base neutralize one another, a point is reached (the
equivalence point
) where the moles of H
+
and OH
-
ions in the solution are equal. After the
equivalence point is reached, continued addition of acid or base creates an excess of H
+
or OH
-
ion
s
in the solution.
Indicators
How would you be able to recognize the equivalence point? An
indicator
is a substance that changes
color due to the presence of excess acid or base. If an appropriate indicator is added to the
Erlenmeyer flask before the titr
ation begins, it will change color after the equivalence point, in
response to the excess H
+
or OH
-
ions. The indicator signals the
endpoint
of the titration.
Choice of Indicators
It is important to note that each indicator has a specific pH range over wh
ich it changes color. Thus,
each titration must use an indicator that changes color near the equivalence point pH (which can be
estimated for each type of titration). For example, bromthymol blue could be used as an indicator for
a titration whose equivale
nce point pH is 6.3, whereas phenolphthalein might act as the indicator for a
titration whose equivalence point pH is 9.0.
You will explore three types of titrations, using the ChemScope
—
titration of a strong acid with a
strong base, titration of a weak a
cid with a strong base, and titration of a weak base with a strong
acid.