Answer:
0.01348 M (mol L-1)
Explanation:
Water can be autoionized:
H2O + H2O ⇄ H3O+ + OH-
This a reversible reaction and then it has a unique constant Kw that at 25ºC it takes the value of 10^-14
[tex]10^{-14} =[H_{3} O+][OH-][/tex]
pH is the concentration of [H3O+] ions in a logaritmic scale:
[tex]pH = -log([H_{3}O+][/tex]
Then you can solve for the [OH-]
[tex][OH-]=(Kw)/(10^{-pH})=(10^{-14})/(10^{-12.03})=0.01348 M[/tex]
Hope it helps!