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Lab1 Sophie Rahman - Lab report for lab 1: analytical measurements
Quantitative Analytical Chemistry Laboratory (CHEM 2800L )
Kennesaw State University
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Report Sheet For: Introduction to Analytical Measurements
Name: Sophie Rahman____________________________
All answers must be typed in black ink. Increase the space between questions to insert your answers. The grading rubric is provided separately.
Prelab Question:
Read the description on page 26 of the textbook on weighing by difference. Write your own description in 25-50 words. Remember this should be in your notebook and it will be in your report. Weigh a capped bottle with dry reagent. Pour some reagent from weighing bottle into receiver and cap the bottle. The difference in mass weighted is the amount delivered. Set initial mass of bottle to 0 with the electronic balance. Deliver reagent from bottle to reweigh from bottle to reweigh bottle. Negative reading is mass of reagent delivered.
Read the description on pages 28-29 about weighing errors. Write your own description in 150-300 words. For this question, you can type it and then print it and cut it out of the paper and tape it into your notebook, rather than writing all of it by hand in your notebook, only to type it for your report. Weighing errors are errors that occur when measuring the weight of an object on a scale. To avoid this, an analytical balance is usually on a marble table to minimize vibrations. The balance is always level so the force can be distributed properly throughout the scale. Weighing magnets might affect the balancing scale so it is recommended to place the magnets on top of a flask that is sitting on the balancing scale. After a sample has dried in the oven, the sample is put into a desiccator, so it does not contain any moisture. Since the scales can become contaminated, there is a calibration that they use. Linearity error is the maximum error that can occur as a result. When you place the item, that is being weighed out, you would want to use an object that would help you avoid touching the item. Fingerprints on the item can affect the item when it is being weighed. Leaving the balance in standby mode helps with minimizing weighing errors. After the balanced is corrected, the reading my change due to the temperature.
Read the description on pages 29-31 about burets. Answer these questions: a. Define parallax. (up to 30 words) Parallax is an error caused by when your eye level is not at the same height as the liquid b. Why is black tape on a white card needed? (up to 30 words)
It makes it easier to locate the precise measurement of the meniscus. Once bottom of meniscus gets dark, it will be easier to read. c. Describe how to deliver a fraction of a drop. (up to 30 words) Open the stopcock slowly, and wait a part is hanging, the close it. Put tip of buret, with drop hanging, inside receiving flask and tap glass wall to transfer drop. d. Describe how to rinse a buret with new solution. (up to 30 words) Once new solution is added to the buret, rinse the buret with new solution by filling half way and tilting buret to wash glass walls.
- Read the description on page 31-32 about Volumetric Flasks. a. Define TC. (up to 10 words) TC is labeled on flasks, stands for To Contain b. Define TD. (up to 10 words) TD is labeled on flasks stands for To Deliver c. Define schlieren. (up to 20 words) Schlieren are streaks that show up before the liquid is homogeneous, regions that refract light differently d. Why is swirling of the liquid important? (up to 30 words) When two different liquids mix, there is small volume change, and the total volume is not the sum of two different liquids. There’s less of a chance to change the volume once you swirl the liquid before thin neck. e. When is the cap/lid/top added to the volumetric flask? (up to 10 words) Once you are done adjusting the correct amount of liquid, you can firmly cap the flask, then invert the flask 10 times.
- Read the description on page 32-33 about Pipets and Syringes. Describe how to use a transfer pipet. Write your own description in 150 -300 words. For this question, you can type it and then print it and cut it out of the paper and tape it into your notebook, rather than writing all of it by hand in your notebook, only to type it for your report.
When using a transfer pipet, you want to use a rubber bulb or suction to suck up the liquid past the calibration mark. Using your mouth is not a viable tool for this process. If liquid gets into the bulb, start over fresh, so the data taken during the given experiment is not altered. Discard a couple pipet volumes of liquid to rinse traces of previous reagents. Quickly replace bulb with index finger at end of pipet and gently press while moving the rubber bulb. Doing this helps prevent liquid from draining below the mark. An alternative to use an automatic suction. Wipe excess liquid off outside of pipet. Touch tip of pipet to the side of beaker and
Beaker Volumetric Flask Graduate Cylinder Erlenmeyer Flask Below Below Above Above
Table 3. Calibration of a Buret Volume Delivered (mL) (VD) (Cumulative)
Mass of H 2 O (g) And beaker Temperature of water: ___19___°C
Mass of 50 mL beaker: 59 _
Mass of H 2 O (g) (Cumulative)
(mass found minus mass of beaker)
Corrected Volume (CV) based on Density (see Part B) ( two decimal places)
Difference from Corrected Volume and Volume Delivered (CV minus VD), i. Correction (mL) 4 64 5 5. 9 69 10 10. 15 74 15 15. 20 79 20 20. 24 84 24 25. 30 89 30 30. 35 94 34 35. 40 99 40 40. 45 104 45 45. 50 109 50 50.
Add the Figure produced from the above data that is similar to Figure 3-3 as found on page 49 of the textbook. Give it a title at the bottom of the figure. Ensure that the axes are labeled correctly. In this case, the dots are connected using the scatter function with straight lines and markers. No trendline or equation of the line is added.
0 10 20 30 40 50 60 0
Calibration Curve of 50-mL Buret
Volume Delivered (mL)
Correction (mL)
Post Lab Questions
In your analysis of Table 1, if the mean mass of the weigh boat is added to the mean mass of the filter paper, does that equal the mean mass of the mass of the weigh boat and the filter paper? Use up to 25 words for your answer. The mean mass of the weigh boat is 3 g, and the mean mass of the filter paper is 0 g. When added together, it is 3 g, and this does not equal the mean mass of the filter paper and weigh boat combined, 3 g.
In your analysis of Table 1, did your breath add any mass to the weigh boat? In your answer that is 30-50 words, describe the precautions that should be taken when using the analytical balance. My breath did add mass to the weigh boat and change the mass of the weigh boat. Precautions with using the analytical balance is to close doors and windows on the balance. This will prevent airflow affecting with the measurements.
In your analysis of Table 2a, how close is the mean volume to the expected volume? Discuss the precision and accuracy found for the 10 mL pipet. Use 30- 50 words. The mean volume, 9 mL, and my expected volume values are not similar. This in turn means they are not accurate. Also, the standard deviation of the expected volume values is .3, and this shows a large deviation between the values. This means the mean volume and expected volume are not precise.
Describe your results for Table 2b in 30-50 words.
Lab1 Sophie Rahman - Lab report for lab 1: analytical measurements
Course: Quantitative Analytical Chemistry Laboratory (CHEM 2800L )
University: Kennesaw State University
