s nensure any volum hOm Canbrated volume. A graduated cylinder is usually not as
ID: 887781 • Letter: S
Question
s nensure any volum hOm Canbrated volume. A graduated cylinder is usually not as accurate or precise as a pipet in delivering volumes. In this experiment, you will calibrate a volumetrie pipet, a stretched micropipet, and a graduated cylinder. You will use the stretched micropipet in later experiments.You need to know how you can increase your accuracy when using mieroscale techniques. You will determine the density of a liquid, a regularly shaped solid, and an irregularly shaped solid. You will record all measurements to the correct number of significant figures to indicate the uncertainty of the measurement. Caleulations made from these measurements must also reflect the correct number of significant figures CAUTION! YOU MUST WEAR DEPARTMENTALLY APPROVED EYE PRO- TECTION AT ALL TIMES YOU ARE IN THE LABORATORY KEEP ALL REACTION VESSELS WELL AWAY FROM YOUR FACE PROCEDURE A. Calibration of Volumetric Pipet and Graduated Cylinder. You will Step 1. (Trial 1) Weigh a clean, dry 10 mL or 25 mL graduated eylinder as accurately as make 3 trials to test reproducibility of your data) possible. (NOTE: Handle the graduated cylinder with erucible tongs to avoid (See Techniques Section C.) Use a 10 mL volumetrie pipet and bulb to carefully pipet 10 mL of distilled water into the weighed graduated cylinder. (NOTE Allow the pipet to drain for 20 seconds after the liquid stops flowing. Then touch the tip to the side of the eylinder wall. Do not blow the liquid out of the pipet!") Read and record the volume of liquid in the graduated cylinder on the REPORT FORM (3). Step 2. Step 3. Step 4. Step 5. Step 6. Step 7. Weigh the graduated cylinder and water as accurately as possible. Record the mass on the REPORT FORM (4). Measure the temperature of water and record the value on the REPORT FORM Dry the graduated cylinder and repeat Steps 1 through 5 to test the reproducibility of your data. Record these data as Trial 2. Use the following density table for water (REPORT FORM Ta) to caleulate the volume of water that was delivered by the pipet (REPORT FORM 7b, 7e). How does the calculated volume delivered by the pipet compare to the calibrated volume of the pipet and the measured volume in the graduated cylinder (REPORT FORM 7d)? Which instrument, the pipet or graduated cylinder, i more accurate in measuring volumes (REPORT FORM 7e)? Density of Water at Several Temperatures Temp. (C) Density (g/mL) 0.9973 24 25 26 Temp. (°C) Density (g/mL) 15 16 0.9991 0.9990 0.9971 0.9968 0.9965Explanation / Answer
The precision of a measurement can be defined as it is related to reproducibility and repeatability, and it is the degree to which repeated measurements under unchanged conditions show the same results. That means if we repeat the same procedure again again and we get the same volumes or they are very closer to one another then they are said to be more precise. So by doing the procedure only one time we can't determine the precision of measurement of the volume delivered by the pipet.
Hence to determine the precision of measurement we have to do the same experiment at least two times.
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