Multiple Choice
Which of the following compounds would make for the best buffer at pH 8?
2. Water
Buffer Solution
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MOPS (pKa =7.2) is a weak acid & acts as a buffer. Calculate the ratio of its basic/acidic species at pH = 6.0.
A
0.098
B
1.24
C
0.377
D
0.063
Verified step by step guidance1
Identify the relevant equation for calculating the ratio of the basic to acidic species in a buffer solution, which is the Henderson-Hasselbalch equation: \( pH = pK_a + \log \left( \frac{[A^-]}{[HA]} \right) \).
Substitute the given values into the Henderson-Hasselbalch equation. Here, \( pH = 6.0 \) and \( pK_a = 7.2 \).
Rearrange the equation to solve for the ratio \( \frac{[A^-]}{[HA]} \): \( \log \left( \frac{[A^-]}{[HA]} \right) = pH - pK_a \).
Calculate the difference \( pH - pK_a \), which is \( 6.0 - 7.2 = -1.2 \).
Use the antilogarithm to find the ratio \( \frac{[A^-]}{[HA]} \): \( \frac{[A^-]}{[HA]} = 10^{-1.2} \).
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