Question

Question #b7814

Answer 1

The `HCl` molecule is formed between a neutral hydrogen atom and a neutral chlorine atom.

Hydrogen has 1 electron in its 1s-orbital, but it needs 1 more to form a stable configuration and complete its 1s-orbital (essentially reaching the configuration of `He`). Chlorine, being in group 17, has 7 electrons in its outermost shell, and needs one more to form a stable octet.

A covalent bond thus forms between `H` and `Cl`, each receiving the extra electron it needed (for more on `HCl`'s covalent bond read about electronegativity).

Now, since `HCl` is a strong acid, it dissociates completely in aqueous solution into `H^(+)`(which form `H_3O^(+)`) and `Cl^(-)` ions as a result of its reaction with water, which acts as a base.

Any further reactions between `HCl` and say, s strong base, will take place between the molecules' ions, like this:

`HCl_((aq)) + NaOH_((aq)) rightleftharpoons NaCl_((aq)) + H_2O_((l))`

`H_3O_((aq))^(+) + Cl_((aq))^(-) + Na_((aq))^(-) + OH_((aq))^(-) rightleftharpoons Na_((aq))^(+) + Cl_((aq))^(-) + 2H_2O_((l))`

The net ionic equation, which is determined by eliminating spectator ions (ions present on both the reactants' and on the products' side) will be:

`H_3O_((aq))^(+) + OH_((aq))^(-) rightleftharpoons 2H_2O_((l))`