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DETERMINATION OF THE GAS CONSTANT INTRODUCTION The ideal gas law, PV = nRT, will be used in this experiment to determine the value for R, the gas constant. Magnesium metal will react with a hydrochloric acid solution to produce hydrogen gas: Mg + 2 HCl → MgCl + H₂ From the mass of magnesium used and the stoichiometry of the reaction, the moles of hydrogen gas that are produced by the above reaction can be calculated. The volume, temperature, and pressure of the gas will be measured, and the value of R can then be calculated. Because the hydrogen gas from this reaction is collected in a eudiometer tube over water, the gas in the tube is a mixture of H₂ and H₂O. The pressure of H, will be calculated by: PH₂=Pas mbeture - VPH,0 (1) Your textbook has a table of the vapor pressure for water at various temperatures. You will have to interpolate to get the vapor pressure at the precise temperature that is in the experiment. If the solution levels inside and outside the eudiometer tube cannot be equalized after the reaction is complete, the pressure of the gas mixture in the tube will not equal atmospheric pressure. In this case, a correction for the differences in height must be made. Measure the difference in heights in millimeters (not centimeters). This difference in height of solutions, which represents the difference in pressures, must be converted into mm Hg units by solving the following: Pheight difference (mmHg) = height difference (mm sol'n) density of soluton density of Hg The density of the solution is 1.01 g/mL. and the density of mercury is 13.534 g/ml. Thus, 53 Pgas mixture Patm-Pheight difference and then, substituting equation (2) into equation (1) yields: PH=Pat-Pheight difference VPH H₂O (2)
PROCEDURE 1. For this experiment, you will have to write a formal lab report. You will also have to create your own data tables which will be included in the lab report. 2. Work in group of 3 to 4 people. Calculate the mass of magnesium necessary to evolve about 40 ml. of hydrogen gas when measured at STP. Obtain two pieces of Mg ribbon and make sure each does not weigh more than the calculated mass. If it is too large, break off a small piece (disposing of the excess in the wastepaper basket) and weigh the remainder. Determine the mass of each piece of Mg ribbon to the nearest 0.0001 g. Do not confuse which piece has which mass. 3. Add 15 ml. of 6-M HCl to the eudiometer tube. With your wash bottle, carefully wash down any acid that might have adhered to the sides of the tube. 4. Coil one of the strips of Mg so that it will fit into the endiometer tube (but not too tight or it reacts too slowly). Slip a piece of copper wire through the coil and secure it. Lower the Mg coil into the eudiometer tube until it is about 8-10 cm below the top of the tube. Secure the wire to the outside of the tube to keep the Mg coil in place. 5- Carefully fill the eudiometer tube to the top with water (layer the water on top of the acid without mixing). Fill your largest beaker about 3/4 full with tap water. Put your thumb over the opening of the endiometer tube (without trapping air bubbles) and invert the eudiometer tube into the beaker. With the open end below water level, remove your thumb and secure the upright tube in a buret clamp. 6. The HCI will diffuse down through the water to the Mg and react with it. As soon as the reaction has stopped, complete the following steps as rapidly as possible. a. Try to adjust the tube so that the levels of liquid inside and outside match. If it can't be done, you must measure the height difference in millimeters. Do not allow the end of the tube to come out of the liquid in your beaker or you will lose your H, gas. b. Measure the volume of gas (±0.01 mL) in the eudiometer tube and convert it to liters. Measure the solution's temperature (10.1°C) and convert it to Kelvin. Use this value for the H, gas temperature. d. Determine the vapor pressure of water using the table to the right to interpolate (See Appendix A and the end of this lab manual) the value for the temperature that you measured in 5.c. 7. Rinse out your tube and repeat steps 2-5 using your second piece of Mg ribbon. 8. Record the current atmospheric pressure in units of mmHg. 9. Straighten the copper wire and leave it with the eudiometer in the clamp on the bench. Leave the eudiometer pointing with the open end down. 10. Exchange data with another group and calculate the experimental value for R (in units of L mmHg mol K¹) using four sets of data. T°C 19.0 20.0 21.0 22.0 23.0 24.0 25.0 26.0 27.0 29.0 30.0 P (torr) 16.49 17:54 18.66 19.83 21.08 22,38 23-78 54 25.21 28.0 28.35 26.74 30.04 31.86 11. Calculate the percent relative average deviation for the four trials (see Appendix A at the end of this lab manual).
55 12. Using your average R value and the accepted value for R which is 62.364 L mmHg mol-¹ K¹, calculate the percent error (see Appendix A at the end of this lab manual). 13. Write a lab report to report the results that you obtained. Included in the report should be: a. An introduction that states what the purpose of the experiment was. What are you being asked to determine? This should be short; no more than 3 or 4 sentences. No numbers are included in this part. b. A procedure which states what you did to accomplish the task set forth in the introduction. Do NOT copy the procedure in this lab manual. Any methodologies used need to be defined as well as any equipment that was used. There should be no numbers included in this part of the lab report. c. Data Tables which give ALL the data taken. You should even include trials that didn't work out but indicate that they didn't work out and why they didn't work out. Any measurement taken should be included here as well as any data that is derived from measurements. For example, you should have a line for the temperature measurement and a line for the conversion of that temperature to Kelvin. d. Example calculations of all calculations done. You only need to show one example of each calculation. e. What results were obtained from the data and the calculations. This should only include the average R value obtained. f. An error discussion that defines the types of error that can occur and gives examples of each one and how those errors, if present, would affect the results. This should also include a discussion of precision and accuracy, how those values are quantified, and what those quantifications indicate. g. Include answers to the questions on the following page with your lab report. h. All pages should be stapled together before turning them in. i. Lab reports do not need to be typed but can be if more convenient.
56 QUESTIONS FOR GAS CONSTANT EXP. 1. There are several sources of error in this experiment that are unavoidable using the available equipment. What are these errors and what can be done to keep them as small as possible? 2. What must be done if the amount of Mg is miscalculated and is so large that the gas generated overflows the tube? 3. A student used 0.0403 g of Mg and collected 39.24 ml. of H, gas over water at 22.7°C on a day when the atmospheric pressure was 743.8 mmHg. The level of the solution in the tube was 11.8 mm above the level in the beaker when the reaction was complete. What was the experimental value for R in units of L mmHg mol K-¹? How does this compare (calculate percent error) to the accepted value for R?
Determination of the Gas Constant Experimental Data Mass of Mg (g) Height difference of liquid (cm) Volume of H2 gas (ml) Temperature of H2 gas (°C) Atmospheric Pressure (mm Hg) Trial 1 0.0432 6.77 45.56 22.3 748.6 Trial 2 0.0446 6.78 46.77 22.4 748.6 Trial 3 0.0410 6.24 42.92 22.2 748.6 Trial 4 0.0398 5.95 41.72 22.5 748.6
T (°C) 19.0 20.0 21.0 22.0 23.0 24.0 25.0 26.0 27.0 28.0 29.0 30.0 Accepted Value of R (L mmHg mol¹K¹) Water Vapor Pressure (torr) 16.49 17.54 18.66 19.83 21.08 22.38 23.78 25.21 26.74 28.35 30.04 31.86 62.363
Introduction The purpose of this experiment is to determine if it is possible to take over the world and, if so, what difficulties would be involved with it. Should it be possible to take over the world, we will have accomplished this at the end of the experiment. All will then bow down to us. Procedure There is a long history of attempts to take over the world. Alexander the Great attempted this in the 4th century BCE. Napoleon Bonapart made another unsuccessful attempt in the 19th century CE. The last attempt was by Adolf Hitler in the mid-20th century CE. All those attempts made use of military superiority to try to beat their neighbors into submission. Because all those attempts failed, we can conclude that a military attempt to take over the world is not viable. As such, other means should be pursued. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec iaculis lacus dui, vel pretium metus mattis vel. Nulla posuere sodales ornare. Ut quis malesuada nisl. Mauris accumsan lacus vel odio dictum, vulputate euismod arcu consequat. Aliquam erat velit, porttitor nec pretium volutpat, congue non nunc. In hac habitasse platea dictumst. Mauris hendrerit neque ut quam viverra, nec faucibus eros interdum. Integer facilisis libero sollicitudin bibendum condimentum. Nam ligula sapien, elementum quis dignissim vel, porttitor eu dolor. Nunc tincidunt metus tortor, et mollis metus ultrices quis. Donec ut tellus non odio finibus rutrum sit amet a sapien. Fusce congue tincidunt lorem, a tempor augue dapibus auctor. Donec lobortis, quam et suscipit ultrices, purus lorem iaculis nibh, ac ullamcorper diam nunc eu magna. Aliquam ut tortor sapien. In eu erat vel massa iaculis iaculis. Nunc nec est rhoncus, semper sem at, ultricies nibh. Suspendisse tristique sollicitudin semper.
Data Tables Attempt number 1 2 3 4 in P₁ = P₁ 1 Sample Calculations ΔΗ = Σ "ΔΗ - Σ "ΔΗ products reactant 2 E A H 1 R R₁ 1 hc n = n²h² 8mL² 1 T T Method of taking over Mind control 7- Twitter and Facebook Cash Subversion through rock music Results of method Zombified population is not satisfactory The Republican party already tried this and failed Not enough cash to do this sustainably Not everyone listens to rock. Would have to use every genre of music. Results The results of this experiment show that it is not likely possible to take over the world. There are far too many complications on a planet with 7.5 billion people and over 180 countries, each of which has multiple different cultures within it. Error Analysis In any experiment there are two main types of error, systematic error and random error. Systematic error arises when praesent leo neque, faucibus ac maximus et, interdum mattis nulla. Nullam imperdiet turpis lectus, in posuere ex volutpat at. Morbi vel mauris convallis, consequat neque ut, imperdiet purus. Proin eget pellentesque tellus, ac rutrum erat. Morbi egestas erat blandit, condimentum risus eu, facilisis arcu. Aenean convallis ex sed elit aliquam faucibus. Donec congue commodo quam at dictum. Vestibulum blandit metus non sodales faucibus. Nam tempor tristique lectus eu tristique. Aliquam eu libero aliquet, accumsan eros et, porttitor quam. Nulla at mauris urna. Morbi commodo, ligula in accumsan convallis, augue orci auctor velit, nec scelerisque enim felis id enim. Pellentesque ac commodo est. Suspendisse sit amet tellus ac sem vestibulum rhoncus. Sed scelerisque condimentumn felis mattis fringilla.
Phasellus tristique interdum rhoncus. Pellentesque lorem dui, accumsan vitae urna tincidunt, suscipit ornare justo. In nec eleifend magna, nec iaculis purus. Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia curae; Maecenas nisl neque, tempor non dui vitae, fringilla commodo tortor. Proin et semper libero, non rhoncus elit. Interdum et malesuada fames ac ante ipsum primis in faucibus. Duis at accumsan risus. Nullam lacinia cursus posuere. Sed sit amet nulla non lorem vestibulum elementum a sed dui. Cras tincidunt nibh et ullamcorper ornare. Nullam vitae lectus ut dolor congue consectetur in a tellus. Suspendisse potenti. Donec ornare laoreet nibh sed aliquet. Morbi commodo dignissim sapien, id efficitur arcu finibus ac. Donec hendrerit maximus nibh, quis tincidunt sem posuere ac. Integer congue faucibus turpis at bibendum. Nulla blandit enim et ligula rutrum lacinia ac bibendum arcu. Mauris iaculis, justo quis rutrum rhoncus, ligula velit auctor quam, non rhoncus urna orci euismod sem. Cras efficitur, metus quis porta vehicula, leo turpis laoreet ex, sed faucibus mauris elit eu urna. Aliquam accumsan metus at iaculis placerat. Sed eu purus arcu. Proin vulputate eu nisi eget mollis. Nulla facilisi. Integer eu ligula id lorem vulputate consequat quis ut mauris. Quisque iaculis maximus lacus id malesuada. Aenean enim nibh, dictum ut fermentum nec, vehicula sit amet nulla. Cras ornare sed tortor quis eleifend. Curabitur in consequat eros. Proin accumsan arcu id ligula placerat sagittis eget ac mi. Morbi commodo, est et laoreet faucibus, felis velit suscipit ipsum, vitae tincidunt tellus justo eu ex. Phasellus eget cursus lacus. Nullam lorem velit, cursus at augue vitae, interdum commodo nunc. Mauris venenatis tincidunt magna a efficitur. Cras accumsan libero nunc, cursus luctus lacus varius ut. Vivamus sed facilisis ligula. Fusce et mattis nunc. Proin at sagittis quam. Duis congue, libero ac gravida elementum, magna mi rutrum nunc, a pharetra elit lorem ut lorem. Donec lobortis nulla turpis, sit amet congue mauris aliquet quis. Suspendisse lorem tellus, viverra sed ante et, porta porta nulla. Vivamus leo urna, gravida eget ante non, vehicula suscipit risus. Cras tempor neque nunc, nec fermentum lectus congue eget. Morbi enim lectus, mollis ut consectetur ac, semper et tortor. Duis ullamcorper efficitur facilisis. Mauris efficitur tortor quis felis gravida dignissim. Any graphs that are generated by and used in the analysis of the data would follow the data tables.