# Question #e2a78

Jul 19, 2015

Because they are the same chemical compound.

#### Explanation:

If I understand your question correctly, hydrogen chloride, or $H C l$, and hydrochloric acid, or $H C l$, have the same chemical formula because they are the same compound.

In essence, a hydrogen chloride molecule is formed when a hydrogen atom and a chlorine atom form a covalent bond.

The fact that chlorine is more electronegative than hydrogen ensures that this bond is actually a polar covalent bond, meaning that the bonding electrons spend more time surrounding the chlorine atom than they do the hydrogen atom.

Now, there is a subtle difference between hydrochloric acid and hydrogen chloride

When the molecule is in a gaseous state, it is called hydrogen chloride.

$H C {l}_{\left(g\right)} \to \textcolor{g r e e n}{\text{hydrogen chloride}}$

When it is placed in aqueous solution, the compound is called hydrochloric acid.

$H C {l}_{\left(a q\right)} \to \textcolor{b l u e}{\text{hydrochloric acid}}$

So basically, the $H C l$ molecule goes by different names depending on which state it is in

• in gaseous state $\to$ hydrogen chloride;
• In aqueous solution $\to$ hydrochloric acid.