Final answer:
To find the concentration of hydronium ions [H3O+] for a solution with a pH of 6.7, we use the formula [H3O+] = 10^(-pH) resulting in [H3O+] = 2.0 × 10^-7 M, indicating a slightly acidic solution.
Step-by-step explanation:
Given that the pH of a solution is 6.7, we can use the formula pH = -log[H3O+] to find the concentration of hydronium ions (also represented as [H+]). The reverse calculation of the pH value allows us to determine this concentration. To calculate the [H3O+], we need to use the antilogarithm (inverse log) of the negative pH value:
[H3O+] = 10^(-pH) = 10^(-6.7)
After performing the calculation, we find that:
[H3O+] = 2.0 × 10^-7 M
This indicates a slightly acidic solution, as the pH is just below 7, which represents a neutral pH in water at 25 °C.