Question

Assume that five weak acids, identified only by numbers (1, 2, 3, 4, and 5) have the following ionization constants: A1 - Ka = 1.0 x 10-3 A2 - Ka = 3.0 x 10-5 A3 - Ka = 2.6 x 10-7 A4 - Ka = 4.0 x 10-9 A5 - Ka = 7.3 x 10-11

Answer 1

Complete question:

Assume that five weak acids, identified only by numbers (1, 2, 3, 4, and 5) have the following ionization constants: A1 - Ka = 1.0 x 10-3 A2 - Ka = 3.0 x 10-5 A3 - Ka = 2.6 x 10-7 A4 - Ka = 4.0 x 10-9 A5 - Ka = 7.3 x 10-11

The anion of which acid is the strongest base? a) A2 b) A5 c) A3 d) A1 e) A4

Answer:

(B) The anion with the strongest base is A5

Explanation:

Acidity of a solution depends on the concentration of H⁺

$K_a = \frac{[H^+]^2}{[HA]}$

Assuming a constant solution molarity (HA), then

$H^+ = \sqrt{K_a}$                                                pH = -Log{H⁺]

For A1: $H^+ = \sqrt{1X10^{-3}} =0.0316$,             pH = 1.5

For A2: $H^+ = \sqrt{3X10^{-5}} =0.00548$,          pH = 2

For A3: $H^+ = \sqrt{2.6X10^{-7}} =0.000509$       pH = 3

For A4: $H^+ = \sqrt{4X10^{-9}} =0.0000633$        pH = 4

For A5: $H^+ = \sqrt{7.3X10^{-11}} =0.00000854$  pH = 5

From the calculation above, the strongest acid is A1 and the weakest Acid is A5.

Therefore, the anion with the strongest base is A5