Why do double displacement reaction occur?

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What's the reason for which double displacement reaction occur? Why there is a need for ion exchange between two compounds? They are already in a bonded state, a stabilised one. So what benefit would a double displacement reaction give?
The ionic reaction
AgNO3 +NaCl - - - - > AgCl(ppt) + NaNO3

(I think that due the reason that Eored for Ag is more than for Na the reaction must have occurred. But still it doesn't seem satisfying.... Please explain. Thanks in advance.)
 

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  • #2
Borek
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They are already in a bonded state, a stabilised one.

Doesn't mean they can't bond better, getting more stabilized.

But your example is trivially wrong - it is not AgNO3 that reacts with NaCl. Write the net ionic reaction and you will see what is really happening.
 
  • #3
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Doesn't mean they can't bond better, getting more stabilized.

But your example is trivially wrong - it is not AgNO3 that reacts with NaCl. Write the net ionic reaction and you will see what is really happening.
AgNO3 and NaCl dissociates into ions in aqueous solution and forms the products mentioned above which are more stable than the reacting compounds. Is this correct?
 
  • #4
Borek
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AgNO3 and NaCl dissociates into ions in aqueous solution and forms the products mentioned above which are more stable than the reacting compounds. Is this correct?

It doesn't say anything about why - and how the situation described differs from - say - the mixture of NaCl and KNO3.
 
  • #5
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NaCl and AgNO3 are both ionic compounds capable of dissociation in water. So when aqueous solutions of both of these compounds are mixed you will have one contain of water which has Na+, Ag+, Cl-, and NO3- ions dissolved in it.

But wait, nothing is stopping these ions from interacting and colliding with one another in the aqueous environment. AgCl is not able to dissolve in water though, so when Ag+ and Cl- find each other, they stay that way as AgCl and crash out (precipitate).

The same dissociation happens when any two soluble ionic compounds are mixed. The difference is, do they for something that is insoluble in the environment they are in or not?
 

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