Respuesta :
Answer:
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
Of the mentioned statements, the correct statement is that a buffer is most resistant to pH change when [acid] = [conjugate base].
What is a buffer?
A solution, which can resist a change in pH upon the addition of the basic or acidic constituents is known as a buffer. It possess the tendency to neutralize small concentrations of added base or acid, thus, sustaining the pH of the solution comparatively stable.
A buffer is more resistant at the range of pH, pKa +/-1.
When [Acid] = [Conjugate base],
[tex]pH = pKa+log\frac{[A-]}{HA} \\pH = pKa+log\frac{1}{1} \\pH = pKa[/tex]
Therefore, when [Acid] = [Conjugate base], a buffer is most resistant to the change in pH.
Thus, the correct answer is option B.
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