In: Chemistry
Part A
Determine the [H3O+] of a 0.250M solution of formic acid.
Express your answer using two significant figures.
[H3O+] = ???
Part B
Determine pH of this solution of formic acid.
Express your answer to two decimal places.
pH=???
Part A:
HCOOH < --------------> COO-(aq) + H3O+(aq)
I 0.250 0 0
C -x +x +x
E 0.250-x +x +x
Ka = [H3O+][COO-] / [HCOOH] = 1.8 x 10^-4
1.8 x 10^-4 = x^2 / (0.250-x)
x^2 + (1.8 x 10^-4)x - (4.5 x 10^-5) = 0
Solving the quadratic equation,
x = 0.0066
Thus, [H3O+] = x = 0.0066 M
----------------------------------------------------------------------------
Part B:
pH = -log[H3O+]
pH = -log(0.0066)
pH = 2.18
Given, 0.250 M of HCOOH (formic acid)
[H3O+]