Calculate the pH of a solution in which

Question

a. [H3O+] = 7.8 x 10-7 M

pH =

b. [H3O+] = 5.1 x 10-6 M

pH =

c. [H3O+] = 6.1 x 10-5 M

pH =

d. [H3O+] = 9.3 x 10-4 M

pH =

I get

8.1
9.5
9.1
6.7

but its wrong please someone help!