Concept:Ammonia gas is evolved when ammonium salts react with bases, not with acids.
Explanation:When an acid is heated with an ammonium salt, ammonia gas is not produced.
Ammonium salts release ammonia only when warmed with a base or alkali.
For example:
NH4Cl+NaOH→NaCl+H2O+NH3.
On the other hand, acids do react with trioxocarbonate(IV) salts to produce carbon dioxide:
2HCl+Na2CO3→2NaCl+H2O+CO2.
Acids also react with alkalis to form salt and water only.
Reactive metals react with dilute acids to form a salt and hydrogen gas.
Thus, options B, C, and D are true chemical properties of acids.
Option A is not a property of acids.
Answer:A. Evolution of ammonia when heated with ammonium salts.