Answer:
According to Bronsted-Lowry, when dissolved in water, an acid can be defined as a proton donor while a base can be defined as a proton acceptor.
Step-by-step explanation:
The proton is usually in the form of hydrogen ions ( H+ ). Consider:
I. HI(aq) + H2O(l) → H30+(aq) + I-(aq)
II. H2O(l) + NH3(aq) → NH4+(aq) + OH-(aq)
In (I), HI donates the H+ to H2O hence HI is a Bronsted-Lowry acid while H2O is a Bronsted-Lowry base. The I-(aq) is called the conjugate base of the acid HI while the H30+ is called the conjugate acid of the base H2O.
In (II), H2O donates the proton to NH3 so H2O is the Bronsted-Lowry acid and NH3 is the Bronsted-Lowry base. The conjugate base is OH- while the conjugate acid is NH4+.
This means that using the Bronsted-Lowry definition, an acid differs from its conjugate base pair only by a proton.
Notice that H2O can function both as a Bronsted-Lowry acid and Bronsted-Lowry base depending on the type of solution as seen above.