In: Chemistry
for the diuretic weak acid H2A Ka1=2.2x10^-6 and Ka2=8.6x10^-9. what is the pH of a .0500M solution of H2A? what are the equilibrium concentrations of H2A and A^2- in this solution?
[H2A] = 0.0500M Ka1= 2.2x10^-6 Ka2 = 8.6x10^-9
H2A ---------------- HA- + H+
Initial 0.0500 0 0
change -x +x +x
equilibrum 0.0500-x +x +x
Ka1 = [HA-][H+]/[H2A]
2.2x10^-6 = x*x/( 0.0500-x)
for solving the equation
x= 0.00033
[HA-] = 0.00033M
[H+] = 0.00033 M
-log[H+] = -log(0.00033)
PH= 3.48
[H2A] = 0.0500 - 0.00033 = 0.04967M
[H2A] = 0.0497M
HA- ---------------- H+ + A-2
0.00033 0.00033 x
Ka2 = [H+][A-2]/[HA-]
8.6x10^-9 = 0.00033x [A-2]/0.00033
[A-2] = 8.6x10^-9M
[H2A] = 0.0497M
PH = 3.48