Action of a buffer is maximum when its pH is

Ans: a (pKa)Ref: Vasudevan & Sreekumari, 6th edi., Pg. 340BUFFERS - are solutions which can resist changes in pH when acid or alkali is added.Composition of buffers - two typesMixtures of weak acid with their salt with a strong base. Mixture of weak bases with their salt with strong acid.Example-Carbonic acid and sodium bicarbonate (bicarbonate buffer)Acetic acid and sodium acetate (acetate buffer)HENDERSON -HASSELBALCH EQUATIONpH = pKa + log / pH= negative log of hydrogen ion concentration pKa = pH at which the acid is half ionized is called pKa of an acid When base or salt =acid, then pH= pKa Therefore, when the concentrations of bases and acid are same, then pH is equal to pKa. Strong acids will have a low pKa and weak acids have a higher pKa.A buffer is most effective when the concentration of salt and acid are equal or when pH = pKa. When the ratio between salt and acid is 10:1, the pH will be 1 unit higher than the pKa.