Experiment 1 Weighing Techniques, Errors, and Statistics PDF

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Summary

Weighing using analytical balance...

Description

Name: Armateo, Fayne Miles Bargas, Ashley Marie Bation, Kate

Date Performed: Group No.

09/11/2019 (Group 1)

Experiment No. 1 Weighing Techniques, Errors, and Statistics I.

Background Laboratory work requires precision and accuracy. The smallest mistake in calculation can lead to erroneous results, thus compromising the credibility and the efficacy of one’s experiment. In line with this, researchers should know how to avoid these mistakes for the sake of better performance. The objectives of this experiment included the proper use of both the top loading as they are often referred to as, is a balance that does not have a draft shield and analytical balance, a balance that has a readability of 0.1 mg or better and has a draft shield. At this level of readability, it is required for the balance to have a draft shield for the sake of accuracy and precision in weighing samples under their usage. With those techniques, the purpose of the experiment branches out to the knowledge of the common sources of errors that could sabotage the work, and lastly; the experiment also sought to teach students about the basic statistics to be used in evaluating basic weighing information. The weighing materials used in this experiment included the Top Loading Balance and the Analytical Balance, the latter used for the coins. The weighing errors tested included the effect of temperature, moisture and evaporation, and electrostatic charge. In addition, the statistical tools that helped compare the results were the Mean, Standard Deviation, Relative Standard Deviation, Dixon’s Q-Test, and the Confidence Interval.

II.

Results Table A1. Weighing by Addition Results Weight of empty weighing bottle (g) Weight of weighing bottle + sample (g) Weight of NaCl (g)

1.60 g 3.42 g 1.82 g

Table A2. Weighing by Difference Results Samples Initial Weight of bottle containing the sample (g) Final Weight of bottle containing the sample (g)

NaOH 87.03 g

EtOH 82.09 g

Sulfur 169.17 g

86.20 g

81.90 g

168.11 g

Weight of sample that was dispensed (g) Weight of empty weighing cup (g) Weight of weighing cup + sample (g) Weight of sample in the weighing cup (g)

0.83 g 1.51 g 2.35 g 0.84 g

0.19 g 1.56 g 1.74 g 0.18 g

0.9 g 1.58 g 2.48 g 0.9 g

Table B1. Effect of Temperature Results Temperature Condition Cold Room Temperature Hot

Weight of Test Tube (g) 42.38 g 42.36 g 42.36 g

Table B2. Effect of Moisture Gain or Evaporation Results Sample NaOH EtOH Sulfur

Net Weight Immediately after Transfer (g) 2.35 g 1.74 g 2.48 g

Net Weight after some Time (g) 2.45 g 1.63 g 2.48 g

Table B2. Effect of Electrostatically Charged Sample Results Initial Weight of Weighing Cup (g) Weight of Weighing Cup after Rubbing with Woolen Cloth (g)

10.76 g 10.77 g

Table C1. Weight of Sample Coins Results Sample Number 1 2 3 4 5 6 7 8 9 10

Weight (g) 5.8803 g 5.9263 g 5.9298 g 5.9365 g 5.9579 g 5.9680 g 5.9823 g 5.9833 g 5.9837 g 5.9993 g

Table C2. Dixon’s Q Test for Outliers Data

Suspect Values H: L:

Qexp 0.131092437 0.3865546218

Qcrit 0.466 0.466

Conclusion Accepted Accepted

Table C3. Summary of Statistical Results Statistical Parameters Mean ( Standard Deviation (s) Relative Standard Deviation (RSD) Confidence Interval at the 95% Confidence Level

Value 5.95474 0.034482117 0.57907007 5.979407021 5.930072979

Figure 1. weighing the weighing cups, weighing cups and sample, NaCl

Figure 2. I weighing the, container of NaOH, weighing cup, weighing cup and NaOH.

Figure 3. weighing the container of EtOH, weighing cup, weighing cup and EtOH

Figure 4. weighing the Container of Sulfur, weighing cups, weighing cup and sulfur.

Figure 5. weighing of NaOH, EtOH and sulfur after ten minutes.

Figure 6.1 Watch Glass at Room Temp.

Figure 6.2 Watch Glass at expose at low temperature

Figure 6.3 watch glass expose at hot temperature.

Figure 7. weighing bottle with induce electrostatic force

Figure 8. Weighing of one peso coins

III.

Discussion The purpose of the experiment was to introduce the students to the basic concept of weighing using an analytical and top loading balance with regards to the possible errors that the researchers may encounter and the statistical tools needed in order to compare small differences between data presented to them. In part one of the experiment, the researchers observed the difference between weighing by addition and weighing by difference. They made the inference that weighing by difference was more accurate as compared to direct weighing because it made observations based on the weight of the container itself rather than just the sample in the weighing cup. Part two of the experiment focused on the possible weighing errors that could affect the accuracy of the results. It included the effect of temperature, like exposing the weighing bottle in either hot or cold temperature, moisture and evaporation leaving the reagents exposed, and electrostatic charge, charges have both a field component and a force component, The field component will attract or repulse particulates. A strong charge on filter paper will attract particulates. Electrostatic force can cause movement in small objects, including the weigh pan of an analytical balance. Static charge attracts particles to weighing samples, transport carriers and scale components. Weighing inaccuracy, sample loss and contamination result. A static charge on samples and other objects in the weighing chamber interacts with the components of the scale, resulting in inaccuracies and “zero” drift, effect of moisture or evaporation, and the effect of electrostatically charged proponent. Increase in temperature did not have any effect on the sample in room temperature, both having equal weights of 42.36 g. A decrease in temperature however slightly increased its weight by 0.02 g. The experiment proceeded with the effect of moisture and evaporation on the samples, NaOH, EtOH, and Sulfur; three of which were set out in room temperature for 10 minutes. The NaOH showed a significant increase in weight, 0.1 g from 2.35 g to 2.45 g – an increase explained by the absorption of moisture. EtOH decreased in weight by 0.11 g (1.74 g – 1.63 g) the loss coming from its evaporation in room temperature. Sulfur, on the other hand was not affected by its exposure to room temperature. Lastly, the researchers electrostatically charged a weighing cup and made the observation that it provided a minuscule increase in weight (0.01 g). Part three of the experiments subjected the researchers to the usage of statistical tools. They weighed ten individual coins and looked for their mean, standard deviation, relative standard deviation, applied Dixon’s Q-Test, and made assumptions as to whether or not the data gathered were valid to be used. The overall mean between their weights was 5.95474 with the standard deviation of 0.034482117 and the relative standard deviation of 0.579070073 which translates to high precision between the clustered information. Its confidence interval at 95% was +5.97940530 and -5.930074693. With regards to the validity and the presence of outliers, Dixon’s Q-Test was also applied with the higher bound being 0.131092437 and the lower bound to be at 0.3865546128, both of which were lower than 0.466 which meant that all the coins were accepted subjects.

IV.

Calculation a. Mean Formula:

Solution: (5.8803 g + 5.9263 g + 5.9298 g + 5.9365 g + 5.9579 g + 5.9680 g + 5.9823 g + 5.9833 g + 5.9837 g + 5.9993 g) / 10 Answer = 5.95474

b. Standard Deviation Formula:

Answer =

0.036347343

c. Relative Standard Deviation Formula:

Answer: 0.610393449 d. Confidence Interval at the 95% Confidence Level Formula:

Answer:

5.979407021 and 5.930072979

e. Dixon’s Q-Test for Outliers Formula:

Answer: All V.

Conclusion

were accepted.

In conclusion, weighing is a technique that should be done correctly in order to produce the appropriate results. One must also take note of the factors that could possibly alter the results such as temperature, moisture and evaporation, and electrostatic charging. According to the results gathered by the researcher, a decrease in temperature causes a slight increase in weight as increasing it barely affects the sample. Absorption of moisture leads to a gain in weight by the sample as evaporation, especially in liquid samples, causes a loss in its weight. Electrostatically charging a material barely makes changes to the sample. As for the data to be used in the experiment, it is important to first subject them to statistical tools in order to test their validity to the experiment as well as for the removal of possible outliers, a benefit presented by Dixon’s Q-Test. Future researchers should acquire and acknowledge these factors in order to promote accurate data and precise information.

VI.

References  Analytical Balance vs Top Loading Balance. (n.d.). Retrieved from https://www.scalesoutlet.com/blog/analytical-balance-vs-top-loading-balance/  Five factors that can affect your weighing system's accuracy. (n.d.). Retrieved from https://www.automation.com/library/articles-white-papers/processweighing/five-factors-that-can-affect-your-weighing-systems-accuracy  Gumkowski, G. (2015, September 7). Eliminating Inaccuracy in Precision Weighing Caused by Static Charge. Retrieved from https://www.labcompare.com/191234-Eliminating-Inaccuracy-in-PrecisionWeighing-Caused-by-Static-Charge/  Outsourcing-Pharma.com. (n.d.). Impurity isolation and sample purification. Retrieved from https://www.outsourcing-pharma.com/Headlines/PromotionalFeatures/Impurity-isolation-and-sample-purification...