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Lab 9: Synthesis of Alum Lab
Download the synthesis of Alum Lab from BU.
http:
people.bu.edu
irubio/ch131/exp03.pdf
Read it over and then watch the 3 videos given below.
Synthesis https:
www.youtube.com/watch?v=-hX4SOiU0rI
Synthesis https:
www.youtube.com/watch?v=eOLx214NKkQ
Al cans: https:
www.youtube.com/watch?v=WAjrjY-JQ3o
Below are images the alum that students produced. The image on the right is more typical, however.
Now go to the lab report form from pages 3-7 to 3-10 and answer the questions on the next page of
this sheet
http:
people.bu.edu
irubio/ch131/exp03.pdf
https:
www.youtube.com/watch?v=-hX4SOiU0rI
https:
www.youtube.com/watch?v=eOLx214NKkQ
https:
www.youtube.com/watch?v=WAjrjY-JQ3o
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Name___________________________
Experiment – Synthesis of Alum
Report the mass of aluminum taken and the mass of alum synthesized.
Suppose you used 1.08 g of Al can to make 16.32 g of alum.
Mass of Al(s) taken = 1.08 g_____
Mass of Alum Obtained = 16.32 g___
(1.a) Balance the equation.
_____Al(s) + ____KOH(aq) + ____H2SO4(aq) + ___H2O(l)  _____KAl(SO4)2∙12H2O(s) + _____H2(g)
(1.b)Calculate the theoretical yield of Alum: 474.4 g Alum/mole, 27.0 g Al/mole
(2.a) Calculate the number of moles of Al(s) you used. Use 27.0 g Al/mole
(2.b) Calculate the number of moles of KOH you used. Concentration of KOH is
mL 1000
KOH moles 4.1
:
(2.c) Calculate the number of moles of H2SO4 you used. Concentration of H2SO4 is
mL 1000
SOH moles 0.9 42
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(3) Given the number of moles of Al(s), KOH, and H2SO4 you calculated in (2), given H2O is present
in large excess, and given the balanced equation of the formation of alum, which substance is the
limiting reagent? Show your calculations, and explain how you a
ived at your answer.
(4) What is the percent yield of alum that you obtained? Show all calculations.
(5) Most students report a percent yield of less than 100%. Which experimental operations contribute
most to not achieving a 100% yield?
BONUS
(6) Calculate the cost of producing a 17-g aluminum from the data given in the report.
(7) Calculate the dollar value of the alum obtained when a 17-g aluminum soda can is completely
converted to alum from the data given.