Calculate the pH of each of the following solutions.

(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:)

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.

Oh ok, thanks!

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

No, the equation pH = -log[H3O+] is the correct equation for calculating the pH of a solution. However, it seems that you made a calculation mistake for part (a). Let's go through the correct calculations for both parts (a) and (b):

(a) [H3O+] = 2.9 x 10^-10 M

To find the pH, you need to take the negative logarithm (base 10) of the hydrogen ion concentration:

pH = -log [H3O+]

pH = -log (2.9 x 10^-10)

Now, when you plug this into a calculator, you should get the correct answer for part (a) as approximately 9.54.

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

Again, using the same equation, we find:

pH = -log [H3O+]

pH = -log (6.4 x 10^-2)

Calculating this, you should get the correct answer for part (b) as approximately 1.19.

So, to summarize:
(a) The correct pH value for [H3O+] = 2.9 x 10^-10 M is approximately 9.54.
(b) The correct pH value for [H3O+] = 6.4 x 10^-2 M is approximately 1.19.