Answer:
The [H3O+] is 1.58x10-12 M.
Explanation:
To calculate the [H3O+] from the pH, we can use the pH formula and replace the value of pH:
[tex]\begin{gathered} pH=-log{}\lbrack H_3O^+\rbrack \\ 11.8=-log\lbrack H_3O^+\rbrack \\ 10^{(-11.8)}=\lbrack H_3O^+\rbrack \\ 1.58*10^{-12}=\lbrack H_3O^+\rbrack \end{gathered}[/tex]So, the [H3O+] is 1.58x10-12 M.