Question

When primary amines are treated with HCl, the product obtained is 
a) an alcohol
b) a cyanide
c) an amide
d) ammonium salt

Answer 1

Hint The nature of $HCl$ is acid and $R - C{H_2} - N{H_2}$ is base. Yes, it is an acid-base reaction. Remember when acid and base react there is formation of salt.
Complete Step-by-step solution:
We know that $HCl$ is a strong acid and $R - C{H_2} - N{H_2}$ (primary amine) is a base. So, in reaction to them ammonium salt is formed. Let’s see what the reaction is.
$HCl + R - C{H_2} - N{H_2} \to R - C{H_2} - NH_3^ + C{l^ - }$
Here a simple acid base reaction happens.
Ammonium salt is a salt that consists of ammonia molecules and ions. These salts are typically colourless, but may also be white or slightly yellow. They are soluble in water and are ionic salts, which means that the ammonium ion is surrounded by two anions. The ammonium ion has a charge of +1, while the anions can have a charge of –1, –2, or –3.
An ammonium salt is a salt formed from an ammonium cation and an anion. Here the ammonium cation is \[R - C{H_2} - NH_3^ + \] and the anion could be any negative ion. When ammonia dissolves in water, it breaks down into $R - C{H_2} - N{H_2}$ and $HCl$. The ammonium ion is created when one of the ammonia molecules loses a hydrogen ion. This happens because ammonia is a basic molecule. The ammonium ion is then able to combine with any negative ion to form a salt. Some common ammonium salts are ammonium chloride, ammonium sulphate, and ammonium nitrate.
The most common type of ammonium salt is ammonium chloride, which is used in fertiliser and as a food additive. Other common examples of ammonium salts include ammonium nitrate and ammonium sulphate. Ammonium salts are also used in various industrial processes, such as the production of drugs, dyes, and explosives.
Ammonium salts have a few important properties that make them useful in these applications. First, they are very soluble in water, which makes them easy to dissolve and transport. They also have a high melting point, which means that they can be used in products that need to be heated. Finally, ammonium salts are very stable, which means that they are not likely to decompose or explode.

So, the correct option d is correct

Note: $HCl$ is a strong acid and $R - C{H_2} - N{H_2}$ (primary amine) is a base. A simple acid -base reaction will happen. So, in reaction to them ammonium salt is formed. Let’s see what the reaction is.
$HCl + R - C{H_2} - N{H_2} \to R - C{H_2} - NH_3^ + C{l^ - }$