You have been asked to determine the pK_a of an unknown acid. In a solution at pH 7.0, you find that 24% of the acid is in its deprotonated form. What is the pK_a of the acid? A)7.9 B)7.5 C)6.5 D)5.6 E)none of the above

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To determine the pK_a, we can use the Henderson-Hasselbalch equation: pH = pK_a + log([A-]/[HA]) where [A-] is the concentration of the deprotonated form of the acid, and [HA] is the concentration of the protonated form. We know that at pH 7.0, 24% of the acid is in its deprotonated form, so [A-]/[HA] = 0.24/0.76 = 0.316. Substituting this into the equation and solving for pK_a, we get: 7.0 = pK_a + log(0.316) pK_a = 7.5 Therefore, the answer is B: 7.5.

You Have Been Asked to Determine the PKa of an Unknown

You Have Been Asked to Determine the PK_a of an Unknown