Which of the following is TRUE? A) An effective buffer has a [base]/[acid] ratio in the range of 10 - 100. B) A buffer is most resistant to pH change when [acid] = [conjugate base] C) An effective buffer has very small absolute concentrations of acid and conjugate base. D) A buffer cannot be destroyed by adding too much strong base. It can only be destroyed by adding too much strong acid. E) None of the above is true.

B is true.

Explanation:

A buffer is the mixture of a weak acid with its conjugate base or vice versa.

An effective buffer has a pH  of pKa ± 1. Using H-H formula:

pH = pKa + log [base] / [acid]

1 = log [base] / [acid]

10 = [base] / [acid]

Or

-1 = log [base] / [acid]

0.1 = [base] / [acid]

In other words, the 1 [base] / [acid] ratio in an effective buffer is between 0.1-100. A IS FALSE

The buffer is most resistant to pH change when pH = pKa. Using H-H formula:

pH = pKa + log [base] / [acid]

0 = log [base] / [acid]

1 = [base] / [acid]

In other words, when [base] = [acid] B IS TRUE

In a buffer, an effective buffer must have a higher concentration of pair acid conjugate base. Thus C IS FALSE

The addition of strong base produce conjugate base decreasing concentration of acid. Too much strong base produce a big  [base] / [acid] ratio destroying buffer. D IS FALSE

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