Orlando 1
Quantitative Analytical Chemistry
Joseph Orlando
Lab #1: Calibration and Choosing Glassware
Purpose:
The objective of this experiment is to calibrate several pieces of volumetric glassware; 1, 2 and 5 mL
pipets as well as 10, 25 and 50 mL volumetric flasks. Statistical analysis will be performed to determine
the accuracy and precision of the measurements taken and to also decide which pipet and volumetric
flask are the most precise/accurate.
Procedure:
Calibration of Pipets
A clean, dry 100mL beaker was weighed five times and the mean mass was calculated. Water was
delivered to the 100mL beaker (following proper pipetting techniques which were discussed in lab) with
1, 2 and 5mL pipettes filled to the appropriate line. This was repeated five times for each pipette. Mass
of the beaker and water delivered via the pipette was recorded and averaged for each pipette. Standard
deviation was also calculated.
Calibration of Volumetric Glassware
10, 25 and 50mL volumetric flasks were cleaned, dried and then weighed five times while empty. The
empty mass was recorded and averaged for each volumetric flask. The flasks were filled to the
appropriate line and mass was recorded. This was repeated five times for each flask and the mass of the
flask plus water was recorded and averaged for each size flask. Standard deviation was calculated.
Data:
Calibration of Pipets
Trial #
Mass (g) of Empty 100 mL Beaker
1
51.0198
2
51.0202
3
51.0201
4
51.0191
5
51.0191
Average Mass
51.0197
Standard Deviation
0.0004
Orlando 2
Trial #
Mass (g) of Flask using 1-mL Pipet
Mass (g) of Water
1
52.0130
0.9938
2
51.9877
0.9680
3
52.0132
0.9935
4
52.0053
0.9856
5
52.0193
0.9996
Avg. Mass:
0.988
Standard Deviation
0.0109
Relative Standard Deviation
1.1032%
Using 2-mL Pipet
Mass (g) of Water
Using 5-mL Pipet
Mass (g) of Water
53.0139
1.9942
55.9878
4.9681
53.0163
1.9966
55.9831
4.9634
53.0021
1.9824
55.9762
4.9565
53.0224
2.0027
55.9720
4.9523
53.0047
1.9850
55.9868
4.9671
Avg. Mass:
1.9921
Standard Deviation
Relative Standard Deviation
4.9614
0.0075
0.0061
0.3764%
0.1229%
Calibration of Volumetric Glassware
Avg. Mass (g) of Empty 10 mL Flask
13.1074
Trial #
Mass (g) 10-mL Flask w/ Water
Mass (g) of Water
1
23.0726
9.9646
2
23.0582
9.9512
3
23.0845
9.9769
4
23.0766
9.9695
5
23.1113
10.0041
Avg. Mass:
9.9732
Standard Deviation
0.0175
Relative Standard Deviation
0.1754%
Orlando 3
Avg. Mass (g) of Empty 25 mL Flask
Avg. Mass (g) of Empty 50 mL Flask
17.9918
48.3933
Mass (g) 25-mL Flask w/ Water
Mass (g) Water
Mass (g) 50-mL Flask w/ Water
Mass (g) Water
42.8726
24.8799
98.0925
49.6985
42.9024
24.9107
98.2089
49.8159
42.9118
24.9199
98.1884
49.7951
42.9102
24.9190
98.1996
49.8062
42.8527
24.8612
98.1936
49.8008
Avg. Mass:
24.8981
49.7833
Standard Deviation
0.0235
0.0429
0.0943%
0.0861%
Relative Standard Deviation
Equations:
𝑀𝑒𝑎𝑛 =
∑𝑖 𝑥𝑖
𝑛
𝑒𝑥𝑎𝑚𝑝𝑙𝑒:
(13.1080 + 13.1070 + 13.1076 + 13.1071 + 13.1072)
= 13.1074
5
𝑆𝑡𝑎𝑛𝑑𝑎𝑟𝑑 𝐷𝑒𝑣𝑖𝑎𝑡𝑖𝑜𝑛
∑𝑖(𝑥𝑖 − 𝑥̅ )2
= √
𝑛−1
(0.9938 − 0.9880) + (0.9680 − 0.9880) + (0.9935 − 0.9880) + (0.9856 − 0.9880) + (0.9996 − 0.9880)2
𝑒𝑥𝑎𝑚𝑝𝑙𝑒: √
4
𝑅𝑒𝑙𝑎𝑡𝑖𝑣𝑒 𝑠𝑡𝑎𝑛𝑑𝑎𝑟𝑑 𝑑𝑒𝑣𝑖𝑎𝑡𝑖𝑜𝑛 = 100 𝑥
𝑠
𝑥̅
𝑒𝑥𝑎𝑚𝑝𝑙𝑒: 100 𝑥
0.0175
= 0.1754
9.9732
Conclusion:
Based on the results of this experiment, it was determined that the 5mL pipet and the 10mL
volumetric flask were the most precise pieces of glassware. This determine was based off of the
standard deviations that were calculated for the different sized glassware. The 5mL pipet and
the 10mL volumetric flask had the smallest standard deviations. The volumetric flasks were
more accurate than the pipets overall. Human error, such as the measurement of the water,
should be considered when observing the calculated deviations from this experiment.
Orlando 4
Post Lab Questions:
1. Explain using calculations and words whether it is better to use 20, 49, or 56 mL of solution from
a 50 mL buret.
It is best to use 49mL of solution when using a 50mL buret. If we were to use 56mL of solution
we would have to fill the buret up twice which would increase the chance for error in our
measurements. Also if were to only use 20mL of solution this would decrease the precision of
the measurement. As the data from the experiment shows, increasing the volume increases the
precision of the measurement.
2. Assuming the volume of base used had a mean value of 43.56 mL with a standard deviation of
0.89 mL using five titrations, the molarity of base was 0.1012 M standard deviation 0.0025, and
the volume of acid had a mean value of 50 mL standard deviation 0.05 mL, what would be the
calculated molarity and error associated with this measurement?
𝑉𝑏𝑎𝑠𝑒 × 𝑀𝑏𝑎𝑠𝑒 = 𝑉𝑎𝑐𝑖𝑑 × 𝑀𝑎𝑐𝑖𝑑
(. 04356 𝐿) × (. 1012 𝑀) = (.050 𝐿) × 𝑀𝑎𝑐𝑖𝑑
𝑀𝑎𝑐𝑖𝑑 = 0.0882 𝑀
Propagation of Error:
.89 𝑚𝐿 2
)
43.56 𝑚𝐿
% 𝐸𝑟𝑟𝑜𝑟 = √(
.0025 𝑚𝐿 2
)
.1012 𝑚𝐿
+(
.05 𝑚𝐿 2
)
50 𝑚𝐿
+(
= 3.21%
Macid = 0.0882 M with 3.21% error, or 0.0882 ± 0.002