How do you calculate the pOH of a solution?

1 Answer
anor277
Jun 6, 2016

In water you use the relationship #pH+pOH=14#.

Explanation:

We know that at #298*K#, equilibrium obtains between hydronium ion and hydroxide ions in water:

#K_w=10^(-14)=[HO^-][H_3O^+]#. We can take #-log_10# of both sides:

#-log_10(K_w)=-log_10[HO^-]-log_10[H_3O^+]=-log_10(10^-14)#

i.e. #-log_10[HO^-]-log_10[H_3O^+]=14# by definition of the log function. And again by definition #pH=-log_10[H_3O^+]# etc.

Thus #pH+pOH=14#. There should be many problems here that use this relationship. Of course, you have to find them. Good luck.

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