Question

Determine the overall balanced equation for the production of alum when given:

1. 2Al(s) + 2KOH(aq) + 6H2O(l) -> 2K[Al(OH)4](aq) + 3H2(g)

2. 2K[Al(OH)4(aq) + H2SO4(aq) -> 2Al(OH)3 + K2SO4(aq) + 2H2O(l)

3. 2Al(OH)3(s) + 3H2SO4(aq) -> 2Al^3+ + 3SO4^2-(aq) + 6H2O(l)

4. K+(aq) + Al^3+(aq) + 2SO4^2-(aq) + 12H2O(l) -> KAI(SO4)2*12H2O(s)

Answer 1

The reactions:

2Al(s) + 2KOH(aq) + 6H2O(l) -> 2K[Al(OH)4](aq) + 3H2(g)

2K[Al(OH)4(aq) + H2SO4(aq) -> 2Al(OH)3 + K2SO4(aq) + 2H2O(l)

2Al(OH)3(s) + 3H2SO4(aq) -> 2Al^3+ + 3SO4^2-(aq) + 6H2O(l)

Balance Al+3:

2K+(aq) + 2Al^3+(aq) + 4SO4^2-(aq) + 24H2O(l) -> 2KAI(SO4)2*12H2O(s)

now, add all

RXN1 + RXN2:

2Al(s) + 2KOH(aq) + 6H2O(l) + 2K[Al(OH)4(aq) + H2SO4(aq)-> 2K[Al(OH)4](aq) + 3H2(g) +2Al(OH)3 + K2SO4(aq) + 2H2O(l)

cancel common terms

2Al(s) + 2KOH(aq) + 4H2O(l) + H2SO4(aq)-> 3H2(g) +2Al(OH)3 + K2SO4(aq)

RXN3 + RXN4

2Al(OH)3(s) + 3H2SO4(aq) + 2K+(aq) + 2Al^3+(aq) + 4SO4^2-(aq) + 24H2O(l) -> 2KAI(SO4)2*12H2O(s) + 2Al^3+ + 3SO4^2-(aq) + 6H2O(l)

cancel common terms

2Al(OH)3(s) + 3H2SO4(aq) + 2K+(aq) + SO4^2-(aq) + 18H2O(l) -> 2KAI(SO4)2*12H2O(s)

Now add both

2Al(s) + 2KOH(aq) + 4H2O(l) + H2SO4(aq)-> 3H2(g) +2Al(OH)3 + K2SO4(aq)

2Al(OH)3(s) + 3H2SO4(aq) + 2K+(aq) + SO4^2-(aq) + 18H2O(l) -> 2KAI(SO4)2*12H2O(s)

we get:

2Al(s) + 2KOH(aq) + 4H2O(l) + H2SO4(aq) + 2Al(OH)3(s) + 3H2SO4(aq) + 2K+(aq) + SO4^2-(aq) + 18H2O(l) -->

3H2(g) +2Al(OH)3 + K2SO4(aq) + 2KAI(SO4)2*12H2O(s)

2Al(s) + 2KOH(aq) +H2SO4(aq) + 3H2SO4(aq) + 2K+(aq) + SO4^2-(aq) + 24H2O(l) --> 3H2(g) +  K2SO4(aq) + 2KAI(SO4)2*12H2O(s)

this can be furhter simpliefied:

2Al(s) + 2K+ +2OH(aq) + 2H+ SO4-2 (aq) + 6H+ + 3SO4-2(aq) + 2K+(aq) + SO4^2-(aq) + 24H2O(l) --> 3H2(g) + 2K+ SO4-2(aq) + 2KAI(SO4)2*12H2O(s)

cancel common terms

2Al(s) + 6H+ + 4SO4-2(aq) + 2K+(aq) + 26H2O(l) --> 3H2(g) + 2KAI(SO4)2*12H2O(s)

Simplified equation

2Al(s) + 6H+ + 2SO4-2(aq) + 2K+(aq) + 26H2O(l) --> 3H2(g) + 2KAI(SO4)2*12H2O(s)