Chemistry Problem dealing with the PH of Formic Acid?

Question

Formic Acid or HC(O2)H loses one proton upon ionization and has a dissociation constant of 1.8 times 10^-4.

a. Calculate the pH of a solution made by adding 2.0 times 10^-2 mole of formic acid to 1.50 liter of solution.

Please show work and explain (after showing work)

Answer 1

HCOOH <> HCOO- + H+
initial concentration
0.02 / 1.5 =0.0133 M

at equilibrium
0.0133 - x . . . .x . . .. . . x

K = 1.8 x 10^-4 = (x)(x) / 0.0133 - x

x = [H+] = 0.00155 M

pH = 2.81

Answer 2

4.6