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I am new to the concept of neutralization. My teacher told me that acids do not react with neutral salts. I want to know why not.

If both are dissolved in water and both completely dissociate, why can't the ions of acid and salt exchange and perform a double displacement reaction.

Moreover I have seen the following reaction in a book: $$\ce{2 NaCl + H2SO4 -> 2 HCl + Na2SO4}$$

paracetamol
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Vatsal Goyal
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    Indeed, they can and sometimes do react. – Ivan Neretin Jan 13 '18 at 09:23
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    That last equation you have there isn't a neutralization reaction ;-) – paracetamol Jan 13 '18 at 10:21
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    This examples shows the danger of uncontrolled generalisations. Whether a reaction can 'happen' or not depends on its thermodynamics and kinetics, and that in turn depends on the species involved. You can't say in general that 'neutral' salts don't react with acids. Take for instance $\ce{Ag2SO4 + 2 HCl <=> 2 AgCl + H2SO4}$. This reaction does happen and has a very high equilibrium constant, because $\ce{AgCl}$ is highly insoluble. Substitute $\ce{Ag}$ with $\ce{Na}$ and then it's the opposite of your example. – user6376297 Jan 13 '18 at 10:53
  • https://chemistry.stackexchange.com/questions/5048/hcl-synthesis-from-sulfuric-acid-and-sodium-salt – Mithoron Jan 13 '18 at 17:37
  • https://chemistry.stackexchange.com/questions/76147/what-are-some-ways-to-predict-that-a-double-replacement-reaction-will-occur?noredirect=1&lq=1 – Mithoron Jan 13 '18 at 18:25

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Neutralization is a reaction between acid and base which results in the formation of a salt and water. When you have any ionic compound and dissolve it into water, dissociation occurs. This means that you get a solution of ions. So if you dissolve acids, bases or salts into water, you end up with a mixture of ions. Then, more things may happen or not.

In the case of the given reaction, you will get a solution with:

$\ce{Na+ + Cl- + H+ + SO4^{2-}}$

If the system is closed, nothing will happen. But if the system is open, then $\ce{HCl}$ will evolve because it is a gas. Since the sulphuric acid is very polar and a liquid, water is not even required. This is, in fact, the standard procedure to prepare anhydrous HCL in the lab. Just drop $\ce{H2SO4}$ on $\ce{NaCl}$. It must be said that $\ce{NH4Cl}$ works better.

Raoul Kessels
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