Answer:
pH = 4.5, concentration = 0.045 M.
pH = 6.5, concentration = 0.175 M.
Explanation:
The ka for the can be calculated by using the formula below;
Ka = 10^-pka = 10^-5.960 = 1.1 × 10^-6
The concentration of hydrogen ion at pH = 4.50 can be calculated as given below;
{H^+ } = 10^-4.50 = 3.2 × 10^-5 M.
(NB=> 10 in this regards means the inverse of log).
The next step is to determine the distribution coefficient which can be calculated by using the formula below;
distribution coefficient = (partition coefficient) × ka / ka + ( concentration of Hydrogen ion,H^+).
distribution coefficient =( 5 × 1.1 × 10^-6 ) / 1.1 × 10^-6 + 3.2 × 10^-5 M. = 5.5 × 10^-6/ 3.2 = 0.00000171875
The fraction remaining from the compound = 45.0 mL / 45.0 mL + (0.00000171875 × 125).
= 0.999995.
Thus, the concentration at pH = 4.5 = 0.999995 × 0.0450 M = 0.045 M
(B). pH=6.50, thus the concentration of Hydrogen ion = 10^-6.5 = 3.2 × 10^-7 M.
distribution coefficient = (partition coefficient) × ka / ka + ( concentration of Hydrogen ion,H^+).
distribution coefficient = (5 × 1.1 × 10^-6)/ 1.1 × 10^-6 + 3.2 × 10^-7 M).
distribution coefficient = 5.5 × 10^-6/ 1.42 × 10^-6 = 3.9.
Therefore, the concentration = 3.9 × 0.0450 M = 0.175 M.
