Question

What is the ideal ratio between the species in the buffer?

What two ratios define the limits of a useful buffer?

Your answer should cover the fundamental definitions in at least two grammatically-correct sentences.

Answer 1

A buffer is formed when a weak acid reacts with a strong base or the salt of its conjugate base or mixture of weak base and its conjugate acid. In this case, since the weak acid can't dissociate to 100%, thus in the solution we willl find ions of both the weak acid and its conjugate base. This mixture is known as Buffer. Generally in buffer, the pH doesn't change much to a little addition of acid or base.

However, if you add more acid or base, then the pH of the mixture will definitely change,. Since buffer is used to maintain a constant pH, thus the ratio of Acid to base should not be changed much. Or The concentration of acid or base should be less than half of the concentration of the buffer at a particular pH.

Thus a buffer is most effective when the concentrations of acid and conjugate base (or base and conjugate acid) are approximately equal. Or in other words, when the log [base]/[acid] equals 0 and the pH equals the pK_a.. The larger the ratio, ie larger defference in the concentration of acid to base, the less effective is the buffer.

As a general rule , the relative amounts of acid and base in a buffer should not differ by more than tenfold i.e 1/10

Thus the 2 ratios are the ratio of acid concentration to the base concentration - limits the effectiveness of buffer.