I thought it was hydrochloride

Step 1: Identify hydrochloric acid.
It is a binary acid consisting of hydrogen and chlorine.
Formula: $\mathrm{HCl}$.

Step 2: Common misconception.
"Hydrochloride" is not the formula for the acid.
Hydrochlorides are salts, e.g., $\mathrm{NaCl}$ (sodium chloride) or organic hydrochlorides like $\mathrm{C_6H_5NH_3Cl}$.

Step 3: Confirm dissociation in water (with units of concentration if needed, but pure formula).
$\mathrm{HCl(aq) \to H^+(aq) + Cl^-(aq)}$

$\mathbf{HCl}$
\mathrm{HCl}