Final answer:
The concentration of dissociated H+ ions in the solution is 3.548 × 10^(-12) M.
Step-by-step explanation:
In an aqueous solution, the pH is a measure of the concentration of H3O+ ions. The pH can be calculated using the formula:
pH = -log[H3O+]
In this case, the pH is given as 11.55. To find the concentration of H3O+ ions in the solution, we can rearrange the formula as:
[H3O+] = 10^(-pH)
Substituting the given pH value, we have:
[H3O+] = 10^(-11.55)
[H3O+] ≈ 3.548 × 10^(-12) M
Therefore, there are approximately 3.548 × 10^(-12) moles of dissociated H3O+ ions in 4.5x10^-1 L of the solution.