Write an activity to show that acids do not have acidic behaviour in the absence of water. (Class 10 CBSE)
Answers
Answer:
A good example is if your lead dry ammonia gas over dry, anhydrous zinc chloride powder. Zinc chloride is a pretty good Lewis acid and ammonia is a Lewis base. You can see the white powder fluff up and become more voluminous. The reaction produces a while solid ammine. (No, not amine)
ZnCl2(s)+2NH3(g)→ZnCl2(NH3)2(s)
In this solid the central zinc atom is surrounded by two chlorine atoms and two nitrogen atoms in a (distorted) tetrahedral arrangement. The Zn<-N bonds are dative bonds formed by the ammonia lone pair.
Another good example is the gas phase reaction between HCl and ammonia. Here the ammonia lone pair attacks the proton rather than a zinc atom. (So the acid is also Brønsted acid, not just Lewis acid). The two gases produce solid salmiak, seen as a smoke:
HCl(g)+NH3(g) =NH4CI(s)