Homework Help

The value if Kw is 9.55*10^-14  at a certain temperature , calculate the pH of water.

user profile pic

shabhi1 | Student, Undergraduate | eNoter

Posted July 5, 2011 at 1:51 AM via web

dislike 0 like

The value if Kw is 9.55*10^-14  at a certain temperature , calculate the pH of water.

1 Answer | Add Yours

Top Answer

user profile pic

giorgiana1976 | College Teacher | Valedictorian

Posted July 5, 2011 at 3:03 AM (Answer #1)

dislike 1 like

We'll recal that Kw = 1*10^-14 mol^2*dm^-6 at 25 Celsius degrees.

Kw is also called the ionic product of water and it varies with temperature.

Kw = [H+]*[OH-]

But [H+]=[OH-] => Kw = [H+]^2

We'll replace the value of Kw:

9.55*10^-14 = [H+]^2

We'll take square root both sides:

[H+] = sqrt 9.55*10^-14

[H+] = 3.09*10^-7

pH = -lg 3.09*10^-7

pH = lg (1/3.09) - lg 10^-7

pH = 7 - 0.48

pH = 6.52

Since pH is smaller than 7, then an acid solution is dissolved in water.

The requested value of pH, if Kw = 9.55*10^-14, is pH = 6.52.

Join to answer this question

Join a community of thousands of dedicated teachers and students.

Join eNotes