ANALYT. METH. & SEP. TECH.
LABORATORY #1A
GRAVIMETRIC CALIBRATION OF A TEN (10) CUBIC
CENTIMETER PIPETTE
LAST NAME, First Name
Presidents College, Golden Grove, GUYANA
1
INTRODUCTION
“An ordinary laboratory pipette may be expected to deliver its nominal volume with good precision and
good accuracy if it is used in the way recommended. In this experiment we investigate the precision and
accuracy of such a pipette by making accurate determinations of the mass of water it delivers in repeated
operations” (Lancashire, 2009).
The true volume of the pipet will be determined indirectly from the mass of a sample of distilled water and
the known density of the water. This procedure will be repeated to give some indication of the precision
of your measurements. The following table gives the volume of 1 g of water at various temperatures. You
will use data from the table to convert the mass measured to the true volume.
Table 1 – Volume of 1g of Water at Various Temperatures (Vogel et al., 1996)
2
AIMS
(a) To record the mass of volume delivered by a ten cubic centimeter pipette;
(b) To evaluate the precision and accuracy of the said pipette by performing simple statistical
analyses;
3
THEORY
Particularly important in Science and Engineering reporting is an inclusion of a concise but informative
section on the underlying principles or theory on which an experiment is premised. This usually takes the
forms of laws, hypotheses, previous research, or formulae that the reader needs in order to understand
the aims of the research. DO NOT repeat the theory section of a lab handout (if one is given). Instead do
your own reading and express the concepts as best you can in your own voice.
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4.1
EXPERIMENTAL
Materials
10.0 cm3 Pipette,
50 cm3 Beaker,
Thermometer,
Pipette Filler,
Graph Paper
ANALYT. METH. & SEP. TECH.
4.2
LABORATORY #1A
Method
1. Collect distilled water in an Erlenmeyer flask and let it stand on the bench for about fifteen (15)
min before determining its temperature.
2. Weigh the beaker on a balance to the nearest tenth of a milligram (i.e. ± 0.001 g).
3. Using a pipette filler, fill the 10 cm 3 pipette with distilled water and discharge into the beaker.
Record the difference in mass.
4. Repeat step 3 until you have the results of four (4) such trials.
5. Determine the temperature of the water you have pipetted prior to and at the end of the
experiment. Take the mean of the two temperatures you have measured as the effective
temperature of the water during the calibration.
Notes:
1. Work in groups of two, and pool all results.
2. Each group must use a DIFFERENT pipette but the members in each group must use the SAME
pipette.
3. You do not need to empty and dry the beaker between trials.
5
RESULTS
Volume of Water, cm3
Group #
Group #1
Group #2
Group #3
𝑉1
𝑉2
𝑉3
𝑉4
𝑉5
𝑉6
𝑉7
𝑉8
Mean, 𝑉̅ (cm3)
Standard Deviation, 𝑠 (cm3)
Table 2 – Insert an appropriate Caption
Group #4
ANALYT. METH. & SEP. TECH.
6
LABORATORY #1A
TREATMENT OF RESULTS
6.1
Mass-Volume Conversion
Use the information in Table 1 to convert the mass of water measured to the volume at the temperature
measured.
Mass of Water at Temperature T, m
(g)
Volume of Water at Temperature T, V
(cm3)
Table 3 – Insert an Appropriate Caption
6.2
̅
Mean, 𝑽
Group # 1
𝑉̅ =
6.3
𝑉1 + 𝑉2 + 𝑉3 + 𝑉4 + 𝑉5 + 𝑉6 + 𝑉7 + 𝑉8
=
8
Standard Deviation, s
Mass of Water, m
(g)
Volume of Water, V
(cm3)
̅ − 𝐕)
Deviations, (𝐕
(cm3)
̅ − 𝐕)𝟐
Sq. Deviations, (𝐕
(cm3)2
̅ − 𝐕)𝟐 =
∑(𝐕
𝑠=
7
∑(𝑉̅ − 𝑉)2
=
𝑛−1
DISCUSSION
State the volume of pipette = V (± s)
Comment on the accuracy and precision of each pipette used.
Discuss possible sources of errors, assumptions, limitations
ANALYT. METH. & SEP. TECH.
LABORATORY #1A
What additional measurements would have been necessary for the conversion of mass to
volume? Explain.
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CONCLUSION
In one sentence or two, state what you have found.
Conclude with respect to your aims.
9
BIBLIOGRAPHY
9.1 Lancashire,
R.,
2009.
CALIBRATION
OF
A
PIPETTE.
[Online]
Available
http://wwwchem.uwimona.edu.jm/lab_manuals/c10expt2.html [Accessed 20 November 2012].
at:
9.2 University of Toronto Writing, 2009. The Lab Report. [Online] Available at:
http://www.writing.utoronto.ca/advice/specific-types-of-writing/lab-report [Accessed 20 November
2012].
9.3 Vogel, A. et al., 1996. Vogel's Textbook of Practical Organic Chemistry (5th Edition). USA: Prentice
Hall.
Notes:
Include ALL references you have consulted during your lab write up!
DO NOT plagiarize someone else’s work.
Reference Style: Harvard