Avogadro's law states that equal volumes of gases, at the same temperature and pressure, contain the same number of molecules. Avogadro's constant(?)is the number of molecules in one mole of any substance, and it is known to be 6.02 x 1023. This laboratory exercise attempts to experimentally verify Avogadro's constant by spreading a monolayer of stearic acid on a known surface area of water. Avogadro's number can be obtained by calculating and dividing the number of stearic acid molecules in a known area of the monolayer by the number of moles of stearic acid in the same area, which can be found through simple calculations involving the mass added and the known molar mass.
[...] This indicates that the experiment, if done without the occurrence of random and systematic error, may be accurate and provide values close to the theoretical constant. Conclusion The experimental value of x 1024, is significantly different from the accepted value of 6.02 x 1023, but it is within one order of magnitude. This indicates that the experiment has the potential to achieve its objective, to determine Avogadro's constant by examining the monolayer of stearic acid on a layer of water, if no random [...]
[...] Relative Standard Deviation of Volume in Readings = .0003/.0199 ml x 100% = Table of Results Water Aliquots of Water Water Deviation of Volume for Part II: Determination of Avogadro's Number Amount of Stearic Acid Added Until Formation of Stearic Acid Monolayer Stearic Acid Added (µL) Aliquots Last Aliquot Diameter of 9.7 Petri Dish Calculations for Part II: Mean Volume of Stearic Acid Used: vbar = [10(.0105ml) + 9(.0105ml) + 9(.0105ml)]/ trials] = 0.098 ml Amount of Moles in Stearic Acid Solution Added Density of Hexane= 0.140 g/L Moles of Stearic Acid Added: 284.47 g/mol Mol = 0.098 ml x ( 0.140 1 x mol/ 284.47 x 1000 ml) = 4.8230 x 10-8 mol 3. [...]
[...] Specifically, the micropipette is a significant source of random error because of the possibilities of inaccuracies that surround it. The experimenter may not have completely pressed the plunger, causing the recorded mass to differ from the actual mass. Air bubbles at the tip of the micropipette introduce another source of error, during both calibration and the second part of the lab, because this leads to inaccurate measurements. Also, when taking the temperature of the water, the thermometer may not have been completely accurate because it was not kept in the environment long enough or it may have touched the glass beaker, which may have had a different temperature than the water itself. [...]
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