A buffered solution is made up of a weak acid and its conjugate base ( or weak base and its conjugate acid ) .Carbonic acid (H2CO3) and bicarbonate ion (HCO3- ) are the examples of this type of pairing .
H+ and Cl- represents strong acids and the conjugate base pair so this cannot make a bufffer solution .
HNO3 and NO3- are also strong acid and its conjugate base pair
Na and NO3- is a salt
Na+ and OH- is a strong base
So, H2CO3 and HCO3- carbonic acid and bicarbonate ion is the only example of a buffer solution since it is made up of a weak acid H2CO3 and its conjugate base HCO3- .
H2CO3 & HCO3- since H2CO3 is a weak acid and HCO3- is its conjugate base.