Experiment 1: The Synthesis of Alum

Topics: Chemistry, Aluminium, Stoichiometry Pages: 1 (439 words) Published: October 21, 2014

Purpose:
This experiment is used to perform a series of synthesis reactions that convert aluminum foil to alum. Alum is used in cooking, to treat wastewater, and is used in common deodorant. In this lab a series of four reactions will occur to yield alum. Calculations:

Aluminum foil: 0.5035 grams
Alum & Watch Glass: 21.7691 grams
Watch Glass: 15.1560 grams
Alum: 6.6131 gram
Theoretical Yield of Alum:
2Al(s) + 2KOH(aq) + 4H2SO4 + 22H20 -> 3H2(g) + 2KAl(SO4)2 + 12H2O(s) 0.5035gAl x 1molAl/ 26.98gAl = 0.0186 mol Al
0.0168molAl x 2molAl / 2mol KAl(SO4)2 = 0.0186mol KAl(SO4)2
0.0186mol KAl(SO4)2 x 258.2g/ mol KAl(SO4)2 = 4.8 gKAl(SO4)2 Theoretical yield = 4.8g KAl(SO4)2
Percent Yield Alum:
6.6131gKAl(SO4)2 / 4.8g KAl(SO4)2 x 100 = 137.77
Percent Yield= 137.77%
Percent Error Alum:
4.8-6.6131 / 4.8 x 100= -37.7
Percent error= 37.7%
Wave Length Alum:
400nm / 10^-9= 4.0 x 10^-7
C=Lambda/nu
3.0 x 10^8=4.0 x 10^-7/nu
Nu=1.33x 10^15 Hz or 1/second
E=hvE=(6.626 x 10^-34 J x S)(1.33 x 10^15 1/S)
E= 8.81 x 10^-19 J energy released
Discussion:
Error is inevitable in any experiment and can happen for various reasons. Some reasons for not getting a 100% may include the crystals still have moisture in them, any incorrect measurments, impurities in solutions, and the fact the crystals kept in the drawer were not weighed at the end. Despite the error alum was formed through the synthesis of aluminum foil proving that this experiment worked. More time spent in lab, more careful measurements, and the elimination of impurities would have dictated a more precise yield. A cloudy participate was made when barium chloride was added to alum and the test indicates the presence of SO42- in the form of BaSO4. A purple flame was produced when alum was placed over the Bunsen burner on the tip of a burn stick. This indicates the wavelength of alum is approximately 400nm; using equations and constants the frequency and energy are obtained. When 1.5 KOH was...

References: General Chemistry 106 Lab Manual, Keystone College
Silberberg, Martin. 2006, 5th edition. Chemistry: The Molecular Nature of Matter and Change.
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