In: Chemistry
Calculate the pH and the equilibrium concentrations of H2C6H5O7-, HC6H5O72- and C6H5O73- in a 0.2370 M aqueous citric acid solution.
For H3C6H5O7, Ka1 = 7.4×10-3, Ka2 = 1.7×10-5, and Ka3 = 4.0×10-7
pH =
[H2C6H5O7-] = ____M
[HC6H5O72-] = ____M
[C6H5O73-] =_____ M
H3C6H5O7 ---------------------------------> H2C6H5O7- + H+
0.2370 0 0 ---------------> initial
0.2370 -x x x -------------------> equilibrium
Ka1 = x^2 / 0.2370-x = 7.4×10-3
x^2 + 7.4×10-3 x - 1.75 x 10^-3 = 0
x = 0.0383
[H+] = 0.0383 M
pH = -log [H+]
pH = 1.42
[H2C6H5O7-] = 0.0383 M
[HC6H5O72-] = 1.7×10^-5
[C6H5O73-] = 1.78 x 10^-10 M