Levi Kastner
The Use of Volumetric Glassware Levi Kastner, Nicholas Whitener, Dawson Wiley Date Lab Was Done: 8-15-2016 Date Lab Was Due: 8-24-2016
Purpose: The purpose of this lab was to get familiar with all of the tools in the lab and to learn how to use them. You need to be familiar with these tools if you are going to use them in the lab precisely and accurately. In this lab, the tools were tested to see which measuring tool was most accurate as well.
Introduction: This lab had two main purposes. The first was to get familiar with and examine the tools used in the chemistry lab. The second purpose, and probably the more important of the two, was to determine which measuring tool was the most precise and accurate. In the lab, we tested 3 different tools. The first was a graduated cylinder. The second tool was a pipet, and the third a tool was a buret. All in all, the lab provided data to support the tool that was best suited for the most precise and accurate measurements. The tools we examined in the lab are tools that you would use frequently in chemistry class. This group of tools consisted of a graduated cylinder, a buret, and a pipet. The first tool we tested was a 25 mL graduated cylinder that measured to the ones(1) place. Because it measured to the ones(1) place, we estimated to the tenths place(1.1). The second tool that we tested was a 25 mL pipet. It measured out to the tenths place (1.1); therefore, we estimated to the hundredths place (1.11). The final tool that we tested was the 50 mL buret. Like the pipet, it also measured to the tenths place(1.1), so we estimated to the hundredths place(1.11) All of these tools were measuring tools, but they all performed differently when it came to judging their accuracy and precision. To test which tools were most accurate, we tried to put 25 mL samples of water into a beaker using each tool. Then, using the temperature of the water, we would figure out the density of the water. Using the density of the water, we used the density formula and the mass of water in the beaker to figure out the real volume of water that was put into the beaker. The tool that got closest to putting the 25 mL of water into the beaker was the most accurate.
Materials: Chemicals:
Levi Kastner
● Tap Water Distilled Water ● Distilled Equipment: ● Squirt Bottle ● Safety Glasses ● Ring Stand ● Clamp ● Calculator ● 25 mL Pipet +/- .01 mL ● Balance +/- .001 grams ● 50 mL Buret +/- .01 mL ● 50 mL Beaker +/- 1 mL ● 1000 mL Graduated Cylinder +/- 1 mL ● 25 mL Graduated Cylinder +/- .1 mL ● 10 mL Graduated Cylinder +/- .01 mL ● 100 mL Graduated Cylinder +/- .1 mL ● Digital Thermometer +/- .1 Degrees Celsius
Pre-lab Questions: 1. Calculate the percentage error arising in an experiment if 1-mL, 5-mL, and 10-mL pipets are used for transfer and each pipet contains 5 drops of water adhering to the inside of the barrel. A single drop of water has an approximate volume of 0.05 mL.
2. If a 0.5-mL air bubble is present in the tip of a buret, what what percent error in 10-mL, 20-mL, and 40-mL samples will result if the air bubble is dislodged during the dispensing of the samples?
Procedure:
(short summary)
In this lab, we did the same experiment with several different pieces of lab equipment to determine which of them was the most accurate. We used the density formula and the mass and volume of several different items and samples of water to determine which piece of equipment was the most accurate. The pieces of equipment tested were as follows: Graduated Cylinder and Beaker, Pipet, and Buret.
Data: The Graduated Cylinder and Beaker: Mass of Empty 25-mL Graduated Cylinder: 68.867 grams
Levi Kastner
Mass of Cylinder Plus Water Sample: 93.619 grams Mass of Water in Cylinder: 24.752 grams Temperature of Water Sample: 23.6 Degrees Celsius Density of Water at This Temperature: .997374 g/mL Calculated Volume of Water Transferred: 24.817 g/mL Difference Between Observed and Calculated Volume: .18mL The 50-mL Beaker: Mass of Empty 50-mL Beaker: 29.893 grams Mass of Beaker Plus Water Sample: 53.734 grams Mass of Water in Beaker: 23.841 grams Temperature of Water Sample: 23.6 Degrees Celsius Density of Water at This Temperature: .997374 g/mL Calculated Volume of Water Transferred: 23.904 mL Difference Between Observed and Calculated Volume: 1 mL The Pipet: Mass of Empty 50-mL Beaker: 29.893 grams Mass of Beaker Plus Water Sample: 55.129 grams Mass of Water Transferred: 25.236 grams Temperature of Water Sample: 24.7 Degrees Celsius Density of Water at This Temperature: .997095 g/mL Calculated Volume of Water Transferred: 25.309 mL Difference Between Actual and Calculated Volume: .31 mL The Buret: Initial Liquid Level in Buret: 0.00 mL Final Liquid Level in Buret: 25.00 mL Volume of Liquid Transferred: 25.00 mL Mass of Empty Beaker: 29.862 grams Mass of Beaker Plus Water: 55.035 grams Mass of Water Transferred: 25.172 grams Temperature of Water: 23.7 Degrees Celsius Density at This Temperature: .997345 g/mL Calculated Volume of Water Transferred: 25.239 mL Difference Between Actual and Calculated Volume: .24 mL
Post-lab Questions: 1. Based on your experiment, briefly discuss the relative precision permitted by a graduated cylinder, pipet, and a buret. Give several circumstances under which you would use each instrument, in preference to the other two.
Levi Kastner
The different instruments used did have somewhat different levels of precision. For us, the graduated cylinder was the most precise. The difference between our actual and calculated volume on it was only .18mL compared to a .31mL difference with the pipet and a .24mL difference with the buret. According to our results, the graduated cylinder is the most precise. It is followed by the buret, which is then followed by the pipet in order of most to least precise. Circumstances under which you would use the graduated cylinder could be when you need as precise a measurement as possible. For example, if you had to have exactly 25 mL of a chemical for an experiment to work, you may want to use a graduated cylinder. When it comes to using the buret, you could use it when you want close measurements, but don’t have to be precise. For example, if you need 25 mL of water for and experiment, and it won’t hurt to have just a little more or a little less, you could make use of the buret. As for the pipet, you can make use of it when it comes to needing rough estimates. If 25-30 ml of water is needed, the pipet will suffice.
Sources of Error: 1. Percent Error of Graduated Cylinder:
2. Percent Error of Pipet:
3. Percent Error of Buret:
Conclusion: After figuring out all of the differences between the calculated and actual volumes, my group was able to determine that the graduated cylinder was the most accurate and precise measuring tool. The difference between the actual and calculated volume for it was .18 mL. The difference between the actual and calculated volume on the pipet was .31 mL, and the difference for the buret was .24 mL. So, in order of most precise/accurate to least precise/accurate, the graduated cylinder was the most precise/accurate, the buret was the second most precise/accurate, and the buret was the least precise/accurate.
