Structure and reactions
Hydrochloric acid is the salt of the hydronium ion , H3O+ and chloride . It is usually prepared by treating HCL with water .
HCL + H2O -HO + CI-
However , the speciation of hydrochloric acid is more complicated than this simple equation implies . The structure of bulk water is infamously complex , and likewise , the formula HO+ is also a gross oversimplification , H+ , present in hydrochloric acid . A combined IR , Raman , X -ray and neutron diffraction study of concentrated solution of hydrochloric acid revealed that the primary form of H+ in these solution is H5O2+ , which along with the chloride anion , is hydrogen – bonded to neighboring water molecules in several different ways , ( In H5O2+ , the proton is sandwiched midway between two water molecules at 180 deg . ) . The author suggests that H3O+ may become more important in dilute HCL solutions .
Hydrochloric acid is a strong acid , since it is completely dissociated in water . It can therefore be used to prepare salts containing the CI- anion called chlorides .
Hydrochloric acid is used in chemical analysis to prepare samples for analysis . Concentrated hydrochloric acid dissolves many metals and forms oxidized metal chlorides and hydrogen gas . It also reacts with besic compounds such as calcium carbonate or copper oxide , forming the dissolved chlorides that can be analyzed .