Respuesta :
Answer:
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
HCN has the most basic pH.
Dissociation constant:
The acidity of a compound can be given in terms of Kₐ value which is the acid dissociation constant. The Kₐ value is directly proportional to the acidity of a molecule.
A large Kₐ value indicates a strong acid because it means the acid is largely dissociated into its ions. A small Kₐ value means little of the acid dissociates, so you have a weak acid. The Kₐ value for most weak acids ranges from [tex]10^{-2}[/tex] to [tex]10^{-14}[/tex].
So out of the following choices, HCN has Kₐ value to be [tex]4.9 * 10^{-10}[/tex] which is the weakest acid since its Kₐ value is the smallest.
The greater the value of Kₐ, the more favored the [tex]H^{+}[/tex] formation, which makes the solution more acidic; therefore, a high Kₐ value indicates a lower pH for a solution.
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