# Why is the half equation of hydrochloric acid 2 H+ + 2 e- H2  What happened to Cl?

A half reaction equation is used to show either the oxidation or the reduction process in the equation.

For the given example, hydrochloric acid dissociates as `HCl -> H^+ + Cl^-` .

The reduction half reaction equation is `2H^+ + 2e^-1-> H_2(g)` .

The `Cl^-` ion combines with the positive ion of the chemical that the acid is reacting with and forms a compound with it. For example, if HCl reacts with sodium metal.

`HCl -> H^+ + Cl^-`

`2H^+ + 2e^-1-> H_2(g)`

and `Na^+ + Cl^(-) -> NaCl`

The Cl in HCl takes part in the other half of the reaction, it is not shown in this half reaction equation as that does not have any relevance here.

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