Hydrogen gas: Hydrogen gas (H2) consists of two hydrogen atoms bonded together. It is one of the reactants involved in forming hydrogen chloride.
Chlorine gas: Chlorine gas (Cl2) consists of two chlorine atoms bonded together. It is another reactant involved in forming hydrogen chloride.
Equilibrium: Equilibrium refers to a state in which the forward and reverse reactions occur at equal rates, resulting in no overall change in the concentrations of reactants and products.