Calculate [H3O+] for each solution.(a) pH = 8.55(b) pH = 11.23(c) pH = 2.87(d) pH = 1.22

 Solution:

The concentration of [OH-] ion and [H3O+]  can be determined as follows   ,

It is known that pH = -log [H3O+]  

   -pH = log [H3O+]

10 -pH  = 10log [H3O+]   or

[H3O+] = 10-pH                                   

   1.0  10-14 

And   [OH-  ]  =  --------------

                              [H3O+]  

Step 1

(a) pH = 8.25

pH = 8.25

The  [H3O+]  from pH =  8.25 can be calculated as follows,

[H3O+] = 10-pH  or  [H3O+] = antilog (- pH)

 8.25 = - log [H3O+]

-  8.25 = log [H3O+]

[H3O+] = 10- 8.25  = 5.62 10-9 M  

                 1.0  10-14       1.0  10-14 

Thus,  [OH-]  =  -------------- =     -----------    = 1.710-6M

         [H3O+]           5.62 10-9

(b) pH = 11.23