Final answer:
The [H3O+] concentration for a 0.200 M solution of HCl is 0.200 M.
Step-by-step explanation:
The [H3O+] concentration for a 0.200 M solution of HCl can be calculated using the equation:
[H3O+] = 0.200 M
Therefore, the [H3O+] concentration for a 0.200 M solution of HCl is 0.200 M.