When methylamine (CH3NH2) reacts with hydrochloric acid (HCl), the product formed is methylammonium chloride (CH3NH3Cl).

Explanation:
Methylamine is a primary amine with the formula CH3NH2, while hydrochloric acid is a strong acid with the formula HCl. When these two substances react, a salt is formed.

The reaction can be represented by the following equation:
CH3NH2 + HCl → CH3NH3Cl

Here is a detailed explanation of the reaction:

1. Formation of Methylammonium Ion:
The reaction starts with the protonation of methylamine by the HCl. The hydrogen ion (H+) from HCl adds to the lone pair of electrons on the nitrogen atom of methylamine, resulting in the formation of the methylammonium ion (CH3NH3+).
CH3NH2 + H+ → CH3NH3+

2. Formation of Methylammonium Chloride:
The methylammonium ion then combines with the chloride ion (Cl-) from HCl to form the salt methylammonium chloride (CH3NH3Cl).
CH3NH3+ + Cl- → CH3NH3Cl

The methylammonium chloride formed in the reaction is an ionic compound composed of positively charged methylammonium ions (CH3NH3+) and negatively charged chloride ions (Cl-). It exists as a solid crystalline compound at room temperature.

The reaction between methylamine and hydrochloric acid is an example of an acid-base reaction, where the acidic HCl donates a proton (H+) to the basic methylamine, resulting in the formation of a salt.

In summary, the product of the reaction between methylamine and HCl is methylammonium chloride (CH3NH3Cl).