Calculate the hydroxide ion concentration of a 0.200 M solution of HCIO4

The concentration of hydroxide ion is  5   10^ − 14  M.

Explanation:

Consider the equilibrium of this acid's dissociation,

                          H C l O 4  ⇌  H +  +  C l O  4 -

Moreover, let's assume that  H C l O 4  is a strong acid and will fully dissociate.

Hence,

                              [ H + ]  =  0.20  M

Now, recall,  

                  K w  =  [ H + ] [ O H − ]  =  1.0   10 ^− 14

Hence,

                  ⇒ [ O H − ]  =  K w  / [ H + ]  = 5   10^ − 14  M.

when [oh-] is 10-5  m, and [h3o+] is 10-9  m, the poh is 5 and ph is 9. again in both cases the sum of ph and poh is 14. however, the hydrogen ion concentration is not always going to be equal to exactly 1 x 10 raised to a negative number. for example, we skipped over the value of 2.0 x 10-7.