Statement I : The acid-base pair that differs only by one proton is called a conjugate acid-base pair.Statement II:  If Bronsted acid is a strong acid then its conjugate base is a weak base and vice-versa.

The acid-base pair that differs only by one proton is called a conjugate acid-base pair. In the example of dissolution of NH3 in H2O,OH- is called the conjugate base of an acid H2O and NH4+ is called conjugate acid of the base NH3. If Bronsted acid is a strong acid then its conjugate base is a weak base and vice-versa. It may be noted that conjugate acid has one extra proton and each conjugate base has one less proton. A strong acid can easily give up its proton to produce a weaker-base.