Calculate the pH of each of the following solutions.

Question

(a) [H3O+] = 2.9 10-10 M- I got 9.5 but its wrong. I used the equation pH= -log[H3O+] Is this the wrong equation?

(b) [H3O+] = 6.4 10-2 M

thanks:)

Answer 1

I think you are doing it correctly. I think you are just reading the calculator wrong (or ignoring the other digits).
pH = -log(H^+) = -log(2.9E-10) = -(-9.5376) = 9.5376 which rounds to 2 significant figures as 9.54. I suspect you are keying your answer into a data base and 9.5 is not right but 9.54 is. I think 9.5376 will be counted wrong, also.

Answer 2

Oh ok, thanks!

Answer 3

Calculate the pH for each of the following solutions at 25 °C.[H³O+] = 1.3 x 10-10 M
pH = -log [H³O]
= -log (13* 10 ^-10)
= 8.89