CHEMISTRY



CHEMISTRYBEANIUM (Bn) LAB NAME__________________ PER_____A SIMULATION OF THE DETERMINATION OF THE AVERAGE MASS OF AN ELEMENT AND ITS ISOTOPES UTILIZING THREE VERY DELICIOUS VARIETIES OF BEANSBackground: Atoms of the same element that have different masses are known as isotopes. The difference in mass between isotopes is the result of these atoms having different numbers of neutrons.An example is the element Uranium. Uranium has three isotopes, each with a different mass and a different % abundance in nature. When we say that the mass of Uranium is 238.029, we have taken the percent abundance of the various isotopes into account. The isotope U-238 is the most abundant form, hence the closeness of the number 238.029 to the number 238. The additional .029 is the result of the other two rarer and heavier isotopes.The Simulation: In our simulation we will not examine the isotopes of Uranium (U) but rather the isotopes of Beanium (Bn). Please note that Bn is not a real element, but just your sick and twisted chemistry teacher’s idea of a joke. We’re playing with beans, plain and simple. Beanium exists in three isotopic forms which are represented by three types of beans: speckled, brown, and white. Unlike real atoms which all have the exact same mass, these beans will vary in mass, but we can do an experiment where we calculate the average mass and use that to help us learn about how average atomic masses are calculated.We will do some calculations along the way, but the main calculation that you should learn from the lab is as follows:average atomic mass = (mass of isotope)(% abundance of isotope) + (mass...)(%...) etc.*** Please note: when using % abundance, you must use the decimal equivalent - for example: 95% = .95, 5% = .05, etc.Equipment: Balance, Evaporating dishMaterials: Lots and lots of beansSafety: Although goggles and aprons are unnecessary, you should be aware that these beans may be covered with anti fungal agents. Not a big deal, unless you eat them, or don’t wash your hands. Just wash your hands after the experiment. Oh yeah, don’t eat them.Procedure:1. Measure the mass of a clean, dry, evaporating dish and record this on the data sheet.2. Use the dish to obtain a sample of Beanium (Bn).3. Separate the Beanium into three different piles (brown, speckled, and white) and count the number of beans in each pile and record those numbers on the data sheet. Add up the total number of beans as well and also record that on the data sheet.4. Using the dish, measure the total mass of each isotope and the evaporating dish and record these numbers on your data sheet. To determine the mass of each isotope alone, subtract the mass of the empty dish from the mass of the dish and the beans and record those numbers on your data sheet.5. Determine the % abundance of each isotope by utilizing the following equation. Show your calculations in the space provided and record the results there. Circle your final answer in that space.% abundance = Total # of each isotope X 100 Total # of beanium atoms6. Determine the average mass of each isotope by taking the mass of each isotope alone and divide it by the total number of atoms of each isotope.example:Average mass of brown isotope =mass of brown isotope alonetotal number of brown atoms7. Using the formula listed on the front page, calculate the average atomic mass of beanium. Record that value in the space provided (this is your experimental value). Remember that you must use the decimal equivalent for percentages.8. Now you will calculate % error for your experiment by comparing your experimental value to the accepted value for the average atomic mass of Bn. The accepted value = _________ amuLab Report Requirements:Your lab report should include:This handout with all of the data charts filled in and calculations completed and shown with appropriate significant figures.A theory and discussion section written on the back of the data sheet that reflects your understanding of the lab. Include sources of error and appropriate vocabularyDATA SHEETMass of empty evaporating dish__________gTotal # of Beanium atoms__________# of speckled atoms__________Mass of dish and speckled atoms__________gMass of speckled atoms alone__________g# of brown atoms__________Mass of dish and brown atoms__________gMass of brown atoms alone__________g# of white atoms__________Mass of dish and white atoms__________gMass of white atoms alone__________gCalculations: Show all work!Percentage abundance of each isotope:SpeckledBrownWhiteAverage mass of each isotope:SpeckledBrown WhiteAverage Atomic Mass of Beanium = % error = T+DIn the beanium lab, students obtained a sample of “beanium,” a fictitious element, in order to learn about isotopes and average atomic mass. Beanium has three isotopes (white, brown, and speckeled) which have different masses and different percent abundances. Students counted and massed the beans in order to calculate average masses of the beans, percent abundance values, and eventually, average atomic mass. Percent error values are typically under 5%. Two reasons for the answers to differ between groups are varying % abundance values that vary with the sample taken and varying average masses of the beans since the beans all have different masses. Students can learn about isotopes from this lab as they work with “different versions of the same element with different masses.” Of course, in elements the reason why different isotopes have different masses is due to differing numbers of neutrons. ................
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