The pH of a 0.17 M solution of a weak monoprotic acid,HA,is 2.92.Calculate the K_a for this acid. A)0.17 B)1.2 $\times$ 10^-³ C)7.1 $\times$ 10^-³ D)8.6 $\times$ 10^-⁶ E)7.3 $\times$ 10^-¹¹

Question

Quizplus · Accepted Answer

The pH of the solution can be used to calculate the pKa of the weak acid using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]) Since the acid is monoprotic, [A-] = [H+], and [HA] = initial concentration of acid. 2.92 = pKa + log([H+]/0.17) pKa = 8.6 The Ka of the acid can be calculated using the equation: Ka = 10^(-pKa) Ka = 1.6 x 10^(-9) Finally, the pKb can be calculated using the equation: pKb + pKa = 14 pKb = 14 - pKa pKb = 5.4 K_a is equal to 10^(-pKb), which is approximately 3.98 x 10^(-6). Therefore, the best choice is D: 8.6 x 10^(-10).

The PH of a 0 ×\times× 10-3 C)7 ×\times× 10-3 D)8 ×\times× 10-6 E)7

The PH of a 0 $\times$ 10^-³
C)7 $\times$ 10^-³
D)8 $\times$ 10^-⁶
E)7