In: Chemistry
The pH of a 0.17-M solution of maleic acid (H2C4H2O4) is measured to be 1.40. Use this information to determine a value of Ka for maleic acid.
H2C4H2O4(aq) + H2O(l) ((double arrow)) HC4H2O4-(aq) + H3O+(aq) Ka =
pH = 1.40
use:
pH = -log [H3O+]
1.40 = -log [H3O+]
[H3O+] = 0.0398 M
H2C4H2O4(aq) + H2O(l) —> HC4H2O4-(aq) + H3O+(aq)
0.17 0 0 (initial)
0.17-x x x (at equilibrium)
here,
[H3O+] = x = 0.0398 M
Ka = [HC4H2O4-][H3O+]/[H2C4H2O4]
Ka = x*x / (0.17-x)
Ka = 0.0398* 0.0398 / (0.17-0.0398)
Ka = 0.012
Answer: 0.012