Final answer:
The ratio of charged to uncharged groups at a given pH can be calculated with the Henderson-Hasselbalch equation and referring to the pKa value. Hydronium ion concentration can be determined from pH by taking the negative exponent of the pH value in base 10.
Step-by-step explanation:
To calculate the ratio of charged to uncharged groups with given pH, we can use the Henderson-Hasselbalch equation, which relates the pH, pKa, and the concentrations of the charged and uncharged species. In the example given where pH is compared with the pKa value of a compound (let's say pKa is 5.23), the ratio of base [B] to its conjugate acid [BH] will dictate the pH value. If the pH is above the pKa, the form which is deprotonated (charged) will be more prevalent. Conversely, if the pH is below the pKa, the protonated (uncharged) form will dominate.
The process of finding concentrations, such as the hydronium ion ([H3O+]) from a known pH, involves converting the pH to the [H3O+] value. This is done by taking the negative exponent to base 10 of the pH value. As explained, if a solution has a pH of 8.3, the hydronium ion concentration ([H3O+]) could be calculated using the appropriate function (10^(-pH)) on a calculator, giving a result of 5.0 × 10⁻⁹ M.