Microscale Lab

Introduction to Microscale Laboratory
Niki Gharavi *, Minh Nguyen
San Jose City College

ABSTRACT: The objective of the experiment was to be introduced to working with the lab equipment, specifically heating and measuring, and to be able to create some of the apparatus that future experiments will require. Heating methods used were an aluminum block, a sand bath, and a water bath. The aluminum block heated most quickly while the others were more stable. Regarding the measurement of water, the less volume of water that was being transferred, the less accurate the measurement turned out to be.
Heating Methods:
Aluminum block:
Heat setting
Temperature ()
Time (minutes)
3
24.1
5:00
4.5
44.3
10:00
3.5
50.0
11:23
3.5
56.0
12:00
1
59.0
13:23
Off
63.0
15:00
The aluminum block heated very quickly, and it was difficult to maintain the
temperature. The experiment needed to be heated at a much slower pace.
Sand bath:
Heat setting
Temperature ()
Time (minutes)
2
26.1
5:00
3
37.1
10:00
2
48.0
15:00
1
50.0
17:00
1
50.0
25:00
The sand bath heated relatively well and was much easier to maintain. However a slower heating would also have been more beneficial.
Water bath:
Heat Setting
Temperature ()
Time (minutes)
2
26.9
5:00
2
32.5
10:00
2
37.1
15:00
2
40.9
20:00
2
43.0
25:00
2
44.2
30:00
2
46.5
40:00
2
47.0
45:00
3
47.0
50:00
3
48.5
55:00
3
50.0
57:00
3
51.0
1 hour
The longest time spent was on the water bath. It was ensured that the heat went up slowly to prevent overheating, however it went slightly over.
Lab experiment 1:
1.0 mL water
Trial
Before (g)
After (g)
1
18.074
19.025
2
18.135
19.061
3
18.161
19.100
Average net difference: 0.939 grams
Percent error: 6.1%
0.20 mL water
Trial
Before (g)
After (g)
1
18.181
18.343
2
18.133
18.313
3
18.123
18.394
Average net difference: 0.204 grams
Percent error: 2.0%
Lab experiment 2:
1.0 mL water
Trial
Before (g)
After (g)
1
18.104
19.230
2
18.104
19.183
3
18.147
19.244
Average net difference: 1.094 grams
Percent error: 9.4%
0.50 mL water
Trial
Before (g)
After (g)
1
18.170
18.751
2
18.119
18.735
3
18.119
18.792
Average net difference: 0.623 grams
Percent error: 4.9%
Discussion:
A.Which volume delivery was most accurate?
The automatic pipet seemed to have the most accurate delivery due to the total combined percent error. (b) Which heating methods were the easiest and the hardest?
The aluminum block was the hardest to maintain since it heated so quickly, the sand bath was in the middle, and the water bath was the easiest to maintain due to the fact that we kept the temperature very low. (c) Speculate the reason why you would need to maintain two roughly calibrated pipets in your drawer throughout the semester
To prevent error within experiments.
(d) List sources of errors and whether these would be positive or negative errors.
Errors in heating were due to the too high het setting the heating methods were placed upon, causing the temperature to rise too high. Errors in measurement may have been inaccurate pipetting of the water, which would have caused a negative effect, increasing the percent error.
(e) Reliability of microscale experiments in general – use % errors in the automated pipets and your calibrated pipets for error
discussion.
The relative reliability is not bad, however it is not extremely accurate either. Percent error ranging from 2.0-9.4 percent error is relatively small for big scale experiments, however in organic chemistry where small measurements may be required, it could pose a large problem.
Conclusions:
(a) Your learning regarding handling of microscale techniques such as volume measuring and heating;
I definitely was able to get a small grasp of when and how to use certain microscale techniques and equipment. Certain heating methods and measuring devices require more accuracy and attention.
(b) Your comfort level in an organic laboratory;
Not quite comfortable yet, however this experiment helped.
(c) Things you might want to improve for future experiments.
I would like to increase patience with heating and pay more attention to detail while pipetting.

Reference:
Pavia, D.; Lampman, G.; Kriz, G.; Engel, R. A Mircoscale Approach to Organic Chemistry Laboratory. 5th edition. Brooks/Cole Cengage Learning. Belmont, CA, 2013, 2-11.