# Do acids react with neutral salts? [duplicate]

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: $$\ce{2 NaCl + H2SO4 -> 2 HCl + Na2SO4}$$

## marked as duplicate by Mithoron, bon, Todd Minehardt, a-cyclohexane-molecule, M.A.R. ಠ_ಠJan 14 '18 at 11:26

• Indeed, they can and sometimes do react. – Ivan Neretin Jan 13 '18 at 9:23
• That last equation you have there isn't a neutralization reaction ;-) – paracetamol Jan 13 '18 at 10:21
• 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
• chemistry.stackexchange.com/questions/5048/… – Mithoron Jan 13 '18 at 17:37
• chemistry.stackexchange.com/questions/76147/… – Mithoron Jan 13 '18 at 18:25

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