m3-avogadros-number-calculation-guide (1)

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Chemistry

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Feb 20, 2024

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Estimating Avogadro’s Number Calculation Guide Activity 1 Calculations Look for the part of the equation in BOLD . That is what you need to solve for. You may need to rearrange some equations. 1. Loop Radius calculation Find the measured thread loop length as described on Page 8, Step 6 of the Investigation Manual. This length is equal to the circumference of the loop. Use the equation Circumferance = 2 π r to find the radius, r in cm. π = 3.14 2. Loop Area Calculation Using the radius determined in #1, determine the area of the thread loop in cm 2 using the equation: Loop Area = π r 2 3. Number of Stearic Acid Molecules Calculation See also Page 6 of the Investigation Manual. Using your Loop Area from #2 and the known area of one Stearic Acid molecule (20.7x10 -16 cm 2 /molecule) determine the number of Stearic Acid molecules using the equation: Loop Area = (# of molecules) x (area of one Stearic Acid molecule) 4. Mass of Stearic Acid Calculation See also Page 5 of the Investigation Manual. Find the Volume of Stearic Acid Dispensed in mL from your data table. Use the equation below to determine the mass of Stearic Acid. Mass of Stearic Acid = Volume in mL Dispensed x 1 L 1000 mL x 0.1 g 1 L 5. Moles of Stearic Acid Calculation See also Page 5 of the Investigation Manual. Use the mass determined in #4, the molar mass of stearic acid (284.5 g/mol) and the equation below to calculate the moles of stearic acid. Moles of Stearic Acid = Mass ¿¿ 4 grams ¿ 284.5 g / mol 6. Avogadro’s Number Calculation See also Page 6 of the Investigation Manual. Use the Number of Stearic Acid Molecules from #3, the Moles of Stearic Acid from #5 and the equation below to determine Avogadro’s Number. Avogadro’s Number = ¿ of molecules ¿ of moles
Activity 2 Calculations 1. Volume of Aluminum Foil Calculation Using the mass of your piece of aluminum foil and the density of aluminum (2.70 g/cm 3 ), determine the volume (in cm 3 ) for the piece of aluminum foil. Density of Aluminum = Mass of Aluminum Volumeof Aluminum 2. Volume of an Aluminum Atom Calculation Using the known radius of an aluminum atom and the “volume of a sphere” equation, determine the volume of an aluminum atom (in cm 3 /atom). Radius of aluminum atom = 1.43x10 -8 cm, Volume of Aluminum Atom ¿ 4 3 πr 3 3. Number of Aluminum Atoms Calculation Using the calculated volume for the piece of aluminum foil in cm 3 from #1 and the calculated volume of an aluminum atom in cm 3 /atom from #2, determine the number of aluminum atoms for the piece of aluminum foil. Number of Aluminum Atoms = Volume of Aluminum Foil Volumeof Aluminum Atom 4. Moles of Aluminum in Foil Using the mass of your piece of aluminum foil and the atomic mass of aluminum (26.98 g/mol), determine the moles of aluminum for the piece of aluminum foil. Atomic Mass of Aluminum = 26.98 g/mol Moles of Aluminum = Mass of Aluminum Foil Atomic Mass of Aluminum 5. Avogadro’s Number Calculation Using the calculated number of aluminum atoms from #3 and the calculated number of moles of aluminum from #4, determine Avogadro’s Number (in atoms/mol). Avogadro’s Number = Number of Aluminum Atoms Molesof Aluminum 6. Area of Aluminum Foil Calculation Using the length and width measurements, calculate the area (in cm 2 ). Area = length x width 7. Foil Thickness Calculation Using the calculated volume from #1 and the calculated area from #6, determine the thickness (in cm) of the piece of aluminum foil.
Volume = area x thickness 8. Aluminum Atom Layers Calculation Using the calculated thickness from #7 and the known diameter of one aluminum atom, determine the number of aluminum atom layers of the piece of aluminum foil. Diameter of aluminum atom = 2.86x10 -8 cm/atom Number of Atom Layers = FoilThickness Diameter of Aluminum Atom 9. % Error Calculation Calculate the % Error for the value of Avogadro’s Number determined in #5 for the aluminum foil piece. % Error = | 6.02 x 10 23 experimental value | 6.02 x 10 23 x 100 10. Adjustment Calculation Because atoms are spherical, there are small gaps between the atoms as they pack together. As a result, aluminum atoms do not occupy the entire volume, but only occupy about 72% of the total volume determined in this experiment. Determine the adjusted value for Avogadro’s number by multiplying your experimentally determined value from #5 by 0.72 (72%). Does this give you a more accurate value for Avogadro’s Number? Determine the % Error for this adjusted value.
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