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Question: introductory organic and biochemistry learning objectives identify molecules as alkanes...

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Introductory Organic and Biochemistry LEARNING OBJECTIVES Identify molecules as alkanes or alcohols. Relate the temperature changes during evaporation to the strength of intermolecular forces of attraction within a sample Predict the intermolecular forces present in a sample. SAFETY Wear goggles at all times. Most of the chemicals used in this lab are respiratory irritants. Hexane is a potenti instructor so they can take proper precautions PROCEDURE Work in pairs. 1. Obtain 2 thermometers from the cart each thermometer with square pieces (-1” x 1つof filter paper secured by small rubber bands. [First slip the rubber band up on the thermometer, then roll the filter paper around the thermometer, and then slip the rubber band over the wrapped paper. The paper should be even with the thermometer end.] Obtain a burette clamp and secure one thermometer to each side of the clamp, with the filter paper end pointing downward 3. Burette clamps can break thermometers if they are clamped too hard. If the clamp is too loose the thermometer could drop and shatter against the lab table. Only tighten enough to hold the thermometer securely a. Pick one thermometer to be thermometer #1 and the other to be thermometer Use tape or some other signage to mark which is which throughout your experiments. 4. PART 2: Ethanol (ethvl acohol) vs. 1-propanol (propyl alcohol) 5. Simultaneously raise the bottles containing the two liquids so that both thermometers are immersed in the liquids. Place thermometer #1 in the ethanol container and thermometer #2 in the 1-propanol container. After the thermometers have been in the liquids for at least 45 seconds make the initial temperature measurement. This will be your thermometer will be for the next few minutes. Write these measurements to two decimal places on the table in the Maximum temperature (C) column. Monitor the temperature for at least fifteen seconds to establish the initial, maximum temperature of each liquid. If the temperature continues to move around, wait until it stabilizes. Then simultaneously lower the bottles from the thermometers. Be sure to put the lid back on each bottle when finished. Intermolecular Forces- Wi9 Last Updated: 1/14/2019 Page 2 of 12
7. Watch the temperature of the thermometers closely. Each partner should watch one thermometer. Once the temperature hits a minimum and starts to increase again, make the final temperature measurement. Record it to two decimal places in the Minimum temperature (C) column. For each liquid, subtract the minimum temperature from the maximum temperature to determine AT, the temperature change during evaporation. 8. 9 Roll the rubber band up the thermometer shaft and dispose of the filter paper in the container in the waste fume hood. Wipe off the temperature thermometer with a paper towel. You may reuse the rubber bands in the next parts of the experiment. a. PART 3:n-Pentane ys. 1-butanol butyl alcohol 10. Repeat Steps 7-11 using n-pentane for thermometer #1 and i-butanol for thermometer #2 Be sure to use two new pieces of filter paper. PART 4: n-Hexane vs, methanol (methvl alcohol) Repeat Steps 7-11 using n-hexane for thermometer #1 and methanol for thermometer #2. Be sure to use two new pieces of filter paper. 11. PART 5: Water vs, methanol (methyl alcohol) Repeat Steps 7-11 using DI water (in a beaker) for thermometer #1 and methanol for thermometer #2. 12. Be sure to use two new pieces of filter paper. olecular Forces- Wi9 Last Updated: 1/14/2019 Page 3 of a2
1. (2 points) On a separate sheet of paper: Write your outline of the procedure for this lab. Include clean-up procedures but exclude lab steward duties. (8 points) Draw the condensed structural formulas and calculate the molar masses (to four significant figures) for each liquid used in this lab. Record your answers in the table 2 below. Water has been completed for you. 2. Table 2: Pre-lab Question #2 Answers Name Ethyl alcohol Propyl Condensed Structural Formula Molar Mass (g/mol) alcohol n-pentane Butyl alcohol n-hexane Methyl alcohol 18.02 H-OH water Page 12 of ia Last Updated: 1/14/2019 Lab 2: Intermolecular Forces - Wi9
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