Experiment 20
Page 215
Dr. Scott Buzby Ph.D.
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An acid-base titration is the determination of
the concentration of an acid or base by exactly
neutralizing the acid/base with an acid or base of
known concentration
This allows for quantitative analysis of the
concentration of an unknown acid or base
solution
It makes use of the neutralization reaction that
occurs between acids and bases and the
knowledge of how acids and bases will react if
their formulas are known
H3O(aq)  OH (aq)  2H 2O(l )
The burette should be rinsed with the standard solution
and an Erlenmeyer flask with distilled water
 Add a known volume of the unknown to the Erlenmeyer
flask, along with a small amount of the indicator chosen
 The known solution should then be allowed out of the
burette, into the conical flask. At this stage we want a
rough estimate of the amount of this solution it took to
neutralize the unknown solution
 Three more titrations should be performed, this time
more accurately, taking into account roughly where the
end point will occur. The readings on the burette at the
end point should be recorded, and averaged to give a final
result. The end point is reached when the indicator just
changes color permanently
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Molarity
grams of sample / molar mass
M
L Solution
 Molarity of Unknown
VA M A  VB M B
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% KHP in Sample
g KHP
% KHP 
Mass of Sample
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The standard deviation of a statistical
population, a data set is the square root of its
variance
Standard deviation is a widely used measure of
variability or dispersion, it shows how much
variation there is from the "average" (mean)
A low standard deviation indicates that the data
points tend to be very close to the mean,
whereas high standard deviation indicates that
the data are spread out over a large range of
values
2
SD 
 Xi  
m 1
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Consider a population consisting of the following values:
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There are eight data points in total, with a mean (or average)
value of 5:
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To calculate the population standard deviation, first compute
the difference of each data point from the mean, and square
the result:
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Next divide the sum of these values by the
number of values and take the square root to
give the standard deviation:
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Therefore, the above has a population
standard deviation of 2
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Report Sheet – Page 223
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Questions – Page 224
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Pre-Lab Experiment 24 – Page 267