Preparation of Alum report - Preparation of Alum, Aluminum...

Preparation of Alum,
Aluminum Potassium Sulfate
Dodecahydrate, from Aluminum
Hoa Chung
Chemistry 1A Spring 2016 February 18, 2016
Objective/Purpose
Calculate the theoretical yield and percent yield of a synthesis reaction.
Theoretical
The equations given below show the complete sequence of reactions involved in our experiment.
1. Reaction of aluminum with KOH (the dissolution step)
2Al(s) + 2 KOH(aq) + 6 H
2
O(l) →2 KAl(OH)
4
(aq) + 3 H
2
(g)
2. Initial addition of sulfuric acid (precipitation of Al(OH)3)
2KAl(OH)
4
(aq) + H
2
SO
4
(aq) →2 Al(OH)
3
(s) + K
2
SO
4
(aq) + 2 H
2
O(l)
3. Further addition of sulfuric acid (dissolving of Al(OH)3)
2Al(OH)
3
(s) + H
2
SO
4
(aq) → Al
2
(SO
4
)
3
(aq) + 6 H
2
O(l)
4. Precipitation of alum on cooling
K
2
SO
4
(aq) + Al
2
(SO
4
)
3
(aq) + 12 H
2
O(l) →2 KAl(SO
4
)
2
⋅ 12 H
2
O(s)
% yield =
actual yield
theoretical yield
x 100
Pre-lab Sections:
Data:

Table 1: Preparation of Alum
Mass of weighing paper (g) 0.3550
Mass of weighing paper + Al foil (g) 1.3551
Mass of Al foil (g) 1.0001
Mass of empty 50 mL beaker (g)