Acid-Base Reaction

  • Thread starter Mozart
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  • #1
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I have to write the complete ionic equation, list the spectator ions, and write the net ionic equation for [tex]H_2SO_4(aq) + NH_4OH(aq)[/tex]

I thought I should attempt to write out the balanced chemical equation so this is what I got.

[tex]H_2SO_4(aq) + 2NH_4OH(aq) \longrightarrow SO_4(NH_4)_2(aq) + 2H_2O(l)[/tex]


I just don't feel right about putting [tex](NH_4)_2(aq)[/tex] with [tex]SO_4(aq)[/tex] I don't know why...

I wont bother writing out what I got for the complete ionic equation, spectator ions, and net ionic equation since it would all be wrong if my balanced chemical reaction was wrong.

Can someone please help me with this first step though. Many many thanks.
 

Answers and Replies

  • #2
PPonte
I think the reaction should be:

[tex]H_2SO_4(aq) + 2NH_4OH(aq) \longrightarrow (NH_4)_2SO_4(aq) + 2H_2O(l)[/tex]

Because,


[tex]H_2SO_4(aq) + 2NH_4OH(aq) \longrightarrow H^+ + SO_4^{2-} + NH_4^+ + OH^-[/tex]

[tex]H^+[/tex] reacts with [tex]OH^-[/tex] to form water.
[tex]NH_4^+[/tex] reacts with [tex]SO_4^{2-}[/tex] to form [tex](NH_4)_2SO_4[/tex], first the cation, then the anion and to have no charge they have to combine 2:1.
 
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  • #3
mrjeffy321
Science Advisor
875
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Sulfuric Acid (H2SO4) is a strong acid, Ammonium Hydroxide (NH4OH) is a weak base, together, they should produce a salt + water.
The salt they would produce would be Ammonium Sulfate [(NH4)2SO4].

H2SO4 (aq) + 2 NH4OH (aq) --> (NH4)2SO4 (aq) + H2O (l)

http://www.jtbaker.com/msds/englishhtml/A6192.htm" [Broken] is soluble in water (41.22 g/100 mL), so it will be in solution in the final product.

Since both the Ammonium ad Sulfate ions are in solution in the reactants and products, in the net ionic equation, they cancel out, leaving just,
H+ (aq) + OH- (aq) --> H2O (l)
 
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  • #4
I thought ammonium hydroxide was a strong base. For any strong acid-strong base reaction, the net ionic equation will be H+ + OH- ---> H2O
 
  • #5
mrjeffy321
Science Advisor
875
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No, Ammonium Hydroxide is a weak base...weak as in it does not completely disassociate when dissolved, unlike H2SO4.

So, actually, I would like to revise my answer.
Since most of the NH4OH is not broken into ions, the net ionic reaction would be,
H+(aq) + NH4OH(aq) --> H2O(l) + NH4+(aq)
The H+ ion from the sulfuric acid will react with the NH4OH to make H2O and leave the Ammonium ion in solution.
 
  • #6
H2SO4 is a strong acid, but HSO4- is a very weak acid...so won't the H2SO4 dissociate into H+ and HSO4- ions and not completely into H+ and SO42- ions?

Maybe I'm way off on this...
 
  • #7
Borek
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ksinclair13 said:
H2SO4 is a strong acid, but HSO4- is a very weak acid...so won't the H2SO4 dissociate into H+ and HSO4- ions and not completely into H+ and SO42- ions?

Maybe I'm way off on this...
Slightly :smile:

HSO4- is weaker, but not as weak as you think. pKa2=2.

0.01M sulfuric acid has pH of 1.85. For a very weak second step you may expect pH=2.00.

Best,
Borek
 
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