0.25 mols of an unknown acid is dissolved in enough water to make 1 Liter of solution. The pH of the solution is 2.19. Determine the ka of the acid from this data.
a. Ka = 6.5 x 10^-3
b. Ka = 4.3 x 10^-4
c. Ka = 1.7 x 10^-4
d. Ka = 5 x 10^-2
e. Ka = 2.7 x 10^-2