HCl molecule transfers an H+ ion (a proton) to a water molecule.
HCl(aq)(acid) + H2O(l)(base) --- H3O+(aq)(conj.acid) + Cl-(aq)(Conj. base)
HCl is a Bronsted acid because it donates the proton"H" to the
Bronsted base "H2O
H2O is a Bronsted base because it is a proton acceptor. as it accepts
H atom from the acid HCl
H3O+ is the conjugate acid as the base accepts a proton ( base + H).
Cl- is the conjugate base as it is (acid-H)
Conjugate Acid-Base Pairs
HX(aq) + H2O(l) <-----> X-(aq) + H3O+(aq)in any acid-base equilibrium both the forward reaction (to the right), and the reverse reaction (to the left), involve proton transfer.
forward reaction HX donates a proton to H2O, so HX is the Bronsted-lowry acid., and H2O is the Bronsted-lowry base.
in the reverse reaction, the H3O+ ion donates a proton to the X- ion, so H3O+ is the acid and X- is the base.
when the acid HX donates a proton, it leaves behind a substance, X- which can act as a base, when H2O acts as a base, it generates H3O+ is the acid, and X- is the base.