Arrhenius and a Bronsted-Lowry Acid
How is hydrochloric acid an arrhenius and a bronsted-lowry acid?
By 1887, Svante Arrhenius proposed definitions for acids and bases, that
somehow are still in common use today. By that definition an acid, in
aqueous solution would:
turn dye litmus from blue to red, react with active metals (as Zn, Fe or Sn)
dissolving it and producing hydrogen gas,react with certain compounds
called alkalis or bases to form water and compounds called salts.
So by that definition hydrochloric acid (HCl in aqueous solution) is an
Arrhenius theory has been modified through the years, as the science
progressed, but was useful for many years and still is used today for many
But...1920 chemists were working with solvents other than water, and
experiments showed that a new theory was needed. One was suggested
in 1923, at almost the same time by J.N.Bronsted (in Copenhagen) and
T.M. Lowry (England) that became knew as the Bronsted-Lowry theory.
By it an acid is defined as a proton donor (an H with a + charge), and a
base as a proton acceptor.
All the substances that Arrehenius considered acids are also acids by
that definition. So the reaction of hydrogen chloride with water has
hydrogen chloride acting as a proton donor, so it is an acid...
Thanks for asking NEWTON!
(Dr. Mabel Rodrigues)
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Update: June 2012