Part A Which of the following is TRUE? . A buffer is most resistant to pH change
ID: 556546 • Letter: P
Question
Part A Which of the following is TRUE? . A buffer is most resistant to pH change when (acidl [conjugate base A buffer has the best resistance to pH change when the buftfor's pH is significantly lower than the pKa of the acid used to make the buffer solution An effective buffer has a [baseacid] ratio in the range of 10-100 The capacity of a buffer cannot be exceeded by adding too much strong base. It can only be exceeded by adding too much strong acid An effective buffer has very small absolute concentrations of acid and conjugate base Submit My Answers Give UpExplanation / Answer
OPTION A. The pH of a buffer is given by Henderson-Hasselbach equation as pH = pKa + ([salt]/[acid]). The maximum moles of acid or base required to effect a pH of one in the buffer solution determines it maximum buffer capacity. Now, If the buffer is subjected to too much acid or base, it will have too much concentration of protons or hydroxide ions which will result in the inhibition of either the salt or the acid (in case of acidic buffer) or the base (in case of basic buffer). This results in excess concentration of both protons and hydroxide ions being possible, if it exceeds the buffers' maximum capacity.
The maximum buffer capacity of a buffer system is maximized when there exist equimolar concentrations of the salt and acid/base. This is because, such a equimolar propotion of both result in rapid equilibrium shift forward and backward at equal rate, thus maintaining pH of the solution as there exists no limiting reagent. This is also why when a buffer's pH is equal to its pKa or pKb, it functions as the best buffer possible for the system.
If the salt:acid/base ratio increases or decreases, there will exist a certain concentration of salt or acid/base that will be ever present, not participating in equilibriating the pH limited by the lower concentration of the other, thus inhibiting the buffer capacity.
Therefore, one can say that when a buffer has salt:acid concentration equal, its pH becomes equal to pKa and that buffer has the maximum efficiency.