According to Bronsted theory of acid and base, an acid in a proton donor while base is a proton acceptor. Acid donates the proton to form conjugate base, while base accepts proton to form corresponding conjugate acid.
For the reaction,
hpo2− 4 (aq) + hno3(aq) ⇔ no− 3 (aq) + h2po− 4 (aq)
In above forward reaction, hno3 donotes proton to form no-3, hence no-3 is a conjugate base.
