lab 1 - EXPERIMENT 1 VOLUMETRIC WARE, DENSITY OF A LIQUID...

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1 EXPERIMENT 1 VOLUMETRIC WARE, DENSITY OF A LIQUID 07F You may do either part A or part B first. To reduce the congestion at the balances, about half of the class should do part A first while the other half does part B first. A. CALIBRATION OF VOLUMETRIC WARE : See Harris, Chapter 2. You will use volumetric glassware in this laboratory and in subsequent laboratories. Consequently, you must learn the use and precision of standard volumetric ware. 1. A pipet is designed to deliver a fixed volume of liquid. Use distilled water to determine the volume of a pipet. Measure the temperature of the distilled water (to ± 0.1 ° C) and use the correct density of water (Harris, Table 2.7 with interpolation or better Eq. 2.4, p. 33-34) to calculate the volume of water delivered from the pipet. {You may use your calculator or Excel to calculate the density of water at the temperature of your measurements.} Weigh (Mass) a small beaker or vial. Use a top-loading balance ( ± 1 mg) for these experiments, not an analytical balance ( ± 0.1 mg). Carefully transfer the correct volume of water from the pipet. Do not blow the last drop of liquid from the pipet. Touch the tip of the pipet to the side of the beaker or vial. Weigh the receiver plus liquid. Some volumetric pipets are calibrated to deliver only a volume of liquid with free drainage. Some pipets have graduations on the sides and the volume delivered is determined by allowing the liquid to flow to the appropriate mark on the side. With this type of pipet, you should not let the liquid flow past the 1.00-mL (or X.00-mL) mark. Pay attention to the pipet that you are using. Repeat the delivery and weighing five times. It is not necessary to use a clean dry receiver for each trial if you perform the experiment properly, but you must weigh the container before each addition of liquid. The data for replicate experiments should/will not be identical. Do not transfer the liquid to the vial (beaker) while the vial (beaker) is on the balance! Top- loading and analytical balances are expensive and sensitive pieces of equipment. Spilled solutions and spilled solids will corrode a balance and cause it malfunction. Apply the buoyancy correction (Harris, Eq. 2.1, p. 24) to each of your weights of water. The correction is small, ~ 0.1 % or ~ 1 ppt of the measured weight (mass). Since the buoyancy effect acts to reduce the mass, your corrected masses should be slightly larger than the measured masses (note the example in Harris). Calculate the density of water at the temperature of your experiments (Harris, Eq. 2.4, p. 33), and then calculate the volume of water delivered by the pipet. There is perhaps some ambiguity about “T” in Eq. 2.4: o C or K. However, you can easily determine which by comparing your calculations with those in Table 2.7. Because the density of water at the temperature of your measurements is less than 1, the volume of water delivered will be numerically larger than the weight of water, although only slightly. Calculate the average and standard deviation of this set of measurements. {Harris, pp. 54
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lab 1 - EXPERIMENT 1 VOLUMETRIC WARE, DENSITY OF A LIQUID...

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