[Polo731]

Hello, I have been trying to figure this problem out for a while. 

The pH of a 1.0 x 10^-8 M hydrochloric acid is not 8.00.  The correct pH can be calculated by considering the relationships between the molarities of the three principal ions in the solution ( H⁺¹, OH^-1, and Cl^-1).  These molarities can be calculated from algebraic equations derived from the considerations below.

a. The solution is electrically neutral.

b. The hydrochloric acid can be assumed to be 100% ionized.

c. The product of the molarities of the hydronium ion and the hydroxide ion must equal K_w.

Calculate the pH of the 1.0 x 10^-8 M HCl solution.

Thanks in advance.

[Yggdrasil]

A good starting point is to convert (a) and (c) into equations and then to use (b) to fill in some of the variables.

[chienbinhnam2324]

We have :
HCl --> H+ + Cl-
H2O <=> H+ + OH-    Kw
[H+] = [Cl-] + [OH-]
<=> [H+] = C(HCl) + Kw/[H+]
Solve that equation , we get [H+] = ? => pH

[AWK]

Put concentration of HCl into Kw= [H3O+][OH-].
then you will get a quadratic equation of type
(c+x)x = 10^-14
where c+x is an actual H3O+ concentration.

[Borek]

At first I have refrained from posting in this thread as Ygg was first with his advice, but now...

http://www.chembuddy.com/?left=pH-calculation&right=pH-strong-acid-base