The pH of a solution is defined as the negative logarithm of the hydrogen ion (H+) concentration. So, pH = -log[H3O+].
To calculate the concentration for a given pH, we can reverse the process and use the exponential function:
[H3O+] = 10^(-pH) = 10^(-13.8) = 1.0 x 10^(-14) M
So, the concentration for a pH of 13.8 is [H3O+] = 1.0 x 10^(-14) M.
Answer: D) [H3O+] = 1.6 x 10-14 M