Question

Identify the substance underlined, in each of the following cases:
A solid formed by the reaction of two gases, one of which is acidic and the other basic in nature.

Answer 1

The reaction mentioned is a confirmatory test for the qualitative analysis of hydrochloric acid and ammonia. The acidic gas would be hydrogen chloride and the basic gas would be ammonia.

Complete step by step answer:
The reaction between hydrogen chloride and ammonia leads to the formation of white coloured fumes and precipitate of ammonium chloride or $N{H_4}Cl$.
$HCl\left( {\text{g}} \right) + N{H_3}\left( {\text{g}} \right) \to N{H_4}Cl\left( {\text{s}} \right)$
This is a classic example of acid-base chemistry.
The lone pair of electrons on the $N$-atom in $N{H_3}$ donated to the electron deficient $H$-atom in $HCl$. Thereby, the chlorine atom takes the shared pair of electrons between it and the hydrogen atom to form chloride ions.
Now, after accepting the${H^ + }$, $N{H_3}$ is converted to $N{H_4}^ +$ and this cation forms an ionic compound ammonium chloride with $C{l^ - }$.
Ammonium Chloride is a very unique compound because the molecule has three different bonds in it. Ionic bond between the ammonium and chloride ions, covalent bond between the nitrogen atom and chlorine atom, and lastly, coordinate covalent bond between the nitrogen atom and the hydrogen atom form hydrogen chloride.
This reaction is a confirmatory test for the qualitative analysis of $HCl$ and $N{H_3}$.

Thus, the solid formed is ammonium chloride or $N{H_4}Cl$

Notes:
1. Ammonium Chloride is a sublime compound.
2. It is commercially known by the name “Sal Ammoniac” and is used as a food additive under the name “E510”.
3. It is mainly used as a nitrogen source for fertilizers.
4. It is used as a flux for metals to be galvanized, tin-coated, or soldered.