All measurements contain random errors. Therefore, whenever a measurement is made in the chemistry laboratory, some uncertainty exists.
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Description
ESTIMATING
THE PRECISION OF PIPET
Introduction:
All
measurements contain random errors. Therefore, whenever a measurement is made
in the chemistry laboratory, some uncertainty exists. It is desirable to keep this uncertainty as
small as possible and obtain measurements that are both precise and
accurate. Precision in the laboratory
implies that when a series of measurements are taken that they will be close in
value to each other. Ideally, our
laboratory glassware and instruments will always be as precise as possible. We
can estimate qualitatively small undetectable uncertainties producing random
error. Random error is cumulative. In this experiment, we will assume that each
error has an equal probability of occurring and that each can cause the final
result to be high or low by a fixed amount.
In this
experiment, you will determine the precision associated with a pipet. Pipets are commonly used in the laboratory to
quickly measure or transfer small amounts of liquids. Many pipets are labeled with the uncertainty
of the pipet. Replicate measurements
using the pipette are recorded on the table provided, this indicates precision
of your measurements.
Purpose: The purpose of this experiment is to estimate
the precision of a 10-mL pipet through practicing the use of Microsoft Excel
manipulation
Result and Data Table:
Activity:
1. Plot a histogram on Microsoft Excel.
2. Determine the mean, median, standard deviation,
maximum, minimum and spread of the data.
3. Comment on the precision. (Hint: Exam the standard
deviation)
4. Write and submit a lab report.
