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Stoichiometry: Preparation of Aluminum - Lab Experiment 4 | CHE 201, Study notes of Chemistry

Experiment 4: Stoichiometry of Aluminum Material Type: Notes; Professor: Fawzy; Class: General College Chemistry; Subject: CHE Chemistry; University: Murray State University; Term: Spring 2010;

Typology: Study notes

2009/2010

Uploaded on 10/19/2010

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Experiment4: Preparation of alum [KAl(SO4)2.12.H2O]
Stoichiometry and the limited reactant concept
The mechanism of formation of alum
2 Al(s) + 2 KOH(aq) + 6 H2O(l) → 2 K[Al(OH)4](aq) + 3 H2(g) (1)
2 K[Al(OH)4](aq) + H2SO4(aq) → 2 Al(OH)3(s) + 2 H2O (l)+ K2SO4(aq) (2)
2 Al(OH)3(s) + 3 H2SO4 → Al2(SO4)3(aq) + 6 H2O (3)
Al2(SO4)3 (aq) + K2SO4(aq) + 24H2O → 2 KAl(SO4)2•12H2O(s) (4)
2 Al(s) + 2 KOH(aq) + 4 H2SO4 + 22 H2O → 2 KAl(SO4)2•12H2O(s) + 3 H2(g) overall reaction
Stoichiometry of the overall reaction
2 moles Al(s) 2 moles alum
2 moles KOH(aq) 2 moles alum
4 moles H2SO4(aq) 2 moles alum
Calculations
1. Calculate number of moles of Al(s):
(g/mol) 98.26
m
)Al(MM
m
n(g) Al
Al
Al
2. Calculate number of moles of KOH:
KOH
KOH VMn
3. Calculate number of moles of H2SO4:
42
42 SOH
SOHVMn
4. Use stoichiometry of the balanced overall reaction to determine the limiting reactant and
the theoretical yield in moles and grams
5. Calculate the % yield

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Experiment4: Preparation of alum [KAl(SO 4 ) 2 .12.H 2 O]

Stoichiometry and the limited reactant concept

The mechanism of formation of alum

2 Al(s) + 2 KOH(aq) + 6 H 2 O(l) → 2 KAl(OH) 4 + 3 H 2 (g) (1)

2 KAl(OH) 4 + H 2 SO 4 (aq) → 2 Al(OH) 3 (s) + 2 H 2 O (l)+ K 2 SO 4 (aq) (2)

2 Al(OH) 3 (s) + 3 H 2 SO 4 → Al 2 (SO 4 ) 3 (aq) + 6 H 2 O (3)

Al 2 (SO 4 ) 3 (aq) + K 2 SO 4 (aq) + 24H 2 O → 2 KAl(SO 4 ) 2 •12H 2 O(s) (4)

2 Al(s) + 2 KOH(aq) + 4 H 2 SO 4 + 22 H 2 O → 2 KAl(SO 4 ) 2 •12H 2 O(s) + 3 H 2 (g) overall reaction

Stoichiometry of the overall reaction

2 moles Al(s) 2 moles alum

2 moles KOH(aq) 2 moles alum

4 moles H 2 SO 4 (aq) 2 moles alum

Calculations

  1. Calculate number of moles of Al(s):
    1. 98 (g/mol)

m

MM(Al)

m n

Al Al(g) Al  

2. Calculate number of moles of KOH:  

KOH (^) KOH n  MV

3. Calculate number of moles of H 2 SO 4 :  

H 2 SO 4 H 2 SO 4 n  MV

  1. Use stoichiometry of the balanced overall reaction to determine the limiting reactant and

the theoretical yield in moles and grams

  1. Calculate the % yield