REPORT
Working with chemicals and a high-form balance with four beams
Oleh :
Nama : Dzira Amara Rahman NIM : 2202442
International Program on Science Education Fakultas Pendidikan Matematika dan Ilmu
Pengetahuan Alam
Universitas Pendidikan Indonesia
A. Date
Thursday, 29th September 2022
B. Objectives:
1. Perform procedures of weighing solid chemicals using a high-form balance with four beams
2. Determine the mass of a given sample
C. Basic Theory
It is crucial to have a full understanding of how to maintain the laboratory balances. It is necessary to use an analytical balance to weigh semimicro and micro amounts. In this practical work you are expected to measure a given sample of oxalic acid accurately. Three times measurement will give more precise of the sample mass. In order to handle the solid appropriately, you need to have sufficient knowledge about it. Thus, you need to find out the answer to the following questions.
What is the characteristic of oxalic acid?
Oxalic acid is a compound dicarboxylate in which the C atoms are able to binds more than one hydroxyl group. This acid has a rhombic crystal form pyramid, colorless and transparent, no odorless and hygroscopic. oxalic acid easily oxidized completely and by the influence of high heat will decompose into CO2 and formic acid. naturally oxalic acid can occur in plants and can be prepared by alkaline extraction of sawmill waste. Oxalic acid can cause irritation to the skin and reduce skin fat when exposed directly and continuously. the symptoms may arise when exposed to oxalic acid are, redness, dry skin and cracked skin.
How to deal with oxalic acid?
We must be careful when we are experimenting with oxalic acid, we must also use Personal Protective Equipment (PPE) in the form of gloves such as chemical resistant gloves or gloves anti heat and liquid chemicals (chemical and liquid protection glove), protective shoes (safety shoes), mask protective equipment, laboratory coats and protective goggles.
D. Materials 1. Oxalic acid 2. Distilled water
E.Apparatuses
1. high-form balance with four beams 2. Watch glass
3. Spatula 4. Wash bottle
F. Procedure N
o
Procedure Observation
1 Clean all the apparatuses All the apparatuses is clean.
2 Remove all objects from the scale for zeroing it. Adjust the knob so the bar on the balance is pointing directly in the centre.
I tried it almost half an hour and it was really difficult and takes patience but in the end it’s balance and I can use it.
3 Fill the scale with the object you want to weigh. Reposition the weights so that the bar once more points directly in the centre. If the bar is slanted upwards, the measurement will read low, and if it is oriented downwards, it will read high.
When I pour oxalic acid on the scale, the bar is slanted
upwards and I should re- balance it to measure the weight of oxalic acid.
4 Look at the measurements that are shown on the first three rows. Do not record any rows that have measurements that are zero. Use the correct significant figures to measure the fourth row
1st : 0 grams in first row, 10 grams in second row, 2 grams in third row and 0,78 grams in fourth row.
2nd : 0 grams in first row, 10 grams in second row, 2 grams in third row and 0,5 grams in
fourth row.
3rd : 0 grams in first row, 10 grams in second row, 2 grams in third row and 0,68 grams in fourth row
5 To determine the object's weight, add the measurements from all four rows together
1st : 0+10g+2g+0,78g = 12,78 2nd : 0+10g+2g+0,5g = 12,5 3rd : 0+10g+2g+0,68g = 12,68 6 Do the procedure for empty
watch glass and watch glass with the crystals three times.
I got different results from the three experiments I've done.
G. Data Analysis
No Experiment Result Result Picture
1 1st 12,78
2 2nd 12,5
3 3rd 12,68
Average 12,73
H. Result and Discussion
Measurements can be uncertain or inaccurate due to interference from both the measuring object and the measuring instrument, so it is
almost certain that there is no measurement result whose value is exactly the same as the actual value of the measured quantity (except by chance).
In other words, a measurement result always contains uncertainty, and therefore the value of the measurement result is not a single value but a range of values. In measurement, errors or uncertainties can occur for various reasons, as follows:
1. General uncertainty (gross error), mostly caused by human error, such as misreading measuring instruments, improper adjustments, improper use of measuring instruments. Uncertainty like this cannot be
expressed mathematically and cannot be avoided as long as humans are involved.
2. Systematic uncertainty (systematic error), caused by the shortcomings of the tool itself, for example damage or environmental conditions that affect the measurement, measuring instrument and or its user. These errors, for example:
a. calibration error;
b. zero point error;
c. the time and service life of the measuring instrument;
d. parallax
3. Random uncertainties (random errors), are unintentional errors caused by causes that cannot be immediately and cannot be directly known because changes in the measurement system occur randomly.
4. Uncertainty due to limitations of abilities and skills of observers can be caused by:
a. limited ability and skills of observers in observing or experimenting;
b. limited ability and skills in mastering measuring instrument
technology. Sophisticated and up-to-date measuring tools are often considered as complicated and difficult to use measuring tools, even though this assumption is not necessarily true.
I. Conclusion
1. The measuring ability of this balance can be changed by shifting the position of the weights along the balance arm.
2. To determine the results of measuring the mass of an object by adding up the scales in the first row with the fourth row that we have moved when we weigh the sample so that it is balanced.
J. Reference
Mastuti, E. (2005). Pembuatan asam oksalat dari sekam padi. Ekuilibrium, 4(1), 13-17.
Diwa, M. A. P. S. (2018). the Correlation of Chemical Exposure and
Personal Hygiene With Irritant Contact Dermatitis Among Workers in the Production Worker. Journal of Vocational Health Studies, 2(1), 8- 13.
Anisah, A. (2019). E Modul Fisika kelas X: besaran dan pengukuran.
Sutrisno, M. P. Pengukuran 2.