Question

Calculate the pH of 5.8 × 10-8 M HCl. Report your answer to the hundredths place.What fraction of the total H in this solution is from the HCl? Report your answer to the hundredths place. The answer is NOT pH=6.80 and H+=.376 or 37.6 or .37must take water into consideration thanks

Answer 1

concentration of HCl = 5.8 x 10^-8 M

HCl is strong acid. so

[H+] = [H+] from HCl + [H+] from water

      = (5.8 x 10^-8 + x ) M

[H+] from water = [OH-] from water = x

Kw = [H+] [OH-]

1.0 x 10^-14 = (5.8 x 10^-8 + x) x

x^2 + 5.8 x 10^-8 x - 1.0 x 10^-14 = 0

x = 7.51 x 10^-8

[H+] = 7.51 x 10^-8 + 5.8 x 10^-8

        = 1.33 x 10^-7 M

pH = -log ( 1.33 x 10^-7)

pH = 6.88

fraction of [H+] = 5.8x10^-8 / 1.33 x 10^-7

                         = 0.44