Which of the following solutions would have the most basic pH? Assume that they are all 0.10 M in acid at 25C. The acid is followed by its Ka value. Group of answer choices HClO2, 1.1 × 10-2 HCHO2, 1.8 × 10-4 HCN, 4.9 × 10-10 HNO2, 4.6 × 10-4 HF, 3.5 × 10-4

Explanation:

Given:

Ka of HClO2 = 1.1 × 10-2

Ka of HCHO2 = 1.8 × 10-4

Ka of HCN = 4.9 × 10-10

Ka of HNO2 = 4.6 × 10-4

Ka of HF = 3.5 × 10-4

All at a concentration of 0.1 M

A.

HA --> H+ + A-

Ka = [H+] × [A-]/[HA]

[H+] = [A-] = x

[HClO2] = 0.1 M

HClO2 --> ClO2^- + H+

1.1 × 10-2 = x^2/0.1

x = sqrt(1.1 × 10^-3

= 0.033 M

pH = -log[H+]

= 1.48

B.

HA --> H+ + A-

Ka = [H+] × [A-]/[HA]

[H+] = [A-] = x

[HCHO2] = 0.1 M

HCHO2 --> CHO2^- + H+

1.8 × 10-4 = x^2/0.1

x = sqrt(1.8 × 10^-5)

= 0.0042 M

pH = -log[H+]

= 2.37

C.

HA --> H+ + A-

Ka = [H+] × [A-]/[HA]

[H+] = [A-] = x

[HCN] = 0.1 M

HCN --> CN- + H+

4.9 × 10-10 = x^2/0.1

x = sqrt(4.9 × 10-11)

= 0.000007 M

pH = -log[H+]

= 5.16

D.

HA --> H+ + A-

Ka = [H+] × [A-]/[HA]

[H+] = [A-] = x

[HNO2] = 0.1 M

HNO2 --> NO2^- + H+

4.6 × 10-4 = x^2/0.1

x = sqrt(4.6 × 10-5)

= 0.0068 M

pH = -log[H+]

= 2.17

E.

HA --> H+ + A-

Ka = [H+] × [A-]/[HA]

[H+] = [A-] = x

[HF] = 0.1 M

HF --> F- + H+

3.5 × 10-4 = x^2/0.1

x = sqrt(3.5 × 10-5)

= 0.0059 M

pH = -log[H+]

= 2.23

a) pH = 1.48

b) pH = 2.37

c) pH = 5.16

d) pH = 2.17

e) pH = 2.33

HCN is most basic because;

smallest Ka

Highest pH value = 5.16

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