Double salt

[elitewarr]

Main Question or Discussion Point

How does double salt reactions work?

Let's say, Cu(NH4)2(SO4)2 + NaOH --> ??
OR maybe Cu(NH4)2(SO4)2 + BaCl2 --> ?

Thanks.

 

[Borek]

Think about each pair of ions seperately.

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methods

 

[elitewarr]

So for the first equation, Cu(NH4)2(SO4)2 + NaOH gives NH3 + CuSO4 + Na2(SO4) + H2O?
Cu(NH4)2(SO4)2 + BaCl2 will give NH3 + BaSO4 + CuCl2 ?

 

[Borek]

Do you know what net ionic reaction is?

You are partially on the right track, partially wrong.

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methods

 

[elitewarr]

Yes. I know what is ionic equation.
So, Cu(NH4)2(SO4)2 break down becomes Cu2+ + 2NH4+ + 2SO4 2-
NaOH will be Na+ and OH-.
So OH- + NH4+ --> NH4OH --> NH3 + H2O ?
and Cu2+ + 2SO4 2- + Na+ --> CuSO4 and Na2SO4?

 

[Borek]

Cu2+ + 2SO4 2- + Na+ --> CuSO4 and Na2SO4?

What you wrote seems to be suggesting that two salts precipitated - that's not the case. If mixed, all three ions are just spectators.

However, one of them can react with OH^- and NH₃...

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methods

 

[elitewarr]

So Cu2+ will react with OH- ? But how do I know which ion will react?

 

[Borek]

Solubility rules - what do you know about solubility of hydroxides?

However, this is more complicated. Ammonia is a good complexing agent and it easily reacts with copper. I am afraid exact outcome depends on the amount of reactants used.

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methods