important, the mathematical calculations must be accurate.
It
is your responsibility to develop methods that ensure correct
calculations. Develop the habit of double-checking. Either you
or the technicians may perform this.
5.
Standardization and Classification
Standardized solutions that are made in the laboratory can be
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broken down into two major categories:
a.
Primary standards.
Primary standards are substances
used as references.
The properties of these standards include
high millequivalent weights greater than 50, high degree of
stability and do not readily absorb atmospheric moisture.
Primary standards usually react completely when neutralized.
They are usually weak acids or bases. Examples of some primary
standards that you may find in the laboratory are KHP, Na2CO3,
and H2C2O4.
b. Secondary standards. Secondary standards function just
as well as primary substances, but there are differences in
their properties.
One main difference is unlike primary
standards, secondary standards are usually strong acids and
bases, and they have low millequivalent weight and are more
hazardous to handle. Examples of secondary standards are acids
such as Hydrochloric (HCL) and Sulfuric (H2SO4) and bases such
as Potassium Hydroxide (KOH) and Sodium hydroxide (NaOH).
6.
Calculations
Titration is a process that helps to determine the concentration
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of unknown solution.
Comparing the volume of the unknown
solution with that of the standard does this.
Since the
concentration
of
the
standard
is
already
known,
the
concentration of the unknown may be calculated by applying the
following functions:
1a.
Normality = number of millequivalent weights
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Number of milliliters of solution
1b.
Number of millequivalents = number of milliequivalents
`(Reaction 1) (Reaction 2)
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1c.
Number of milliequivalents = Normality x milliliters
3-4
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