Final answer:
To calculate the buffer solution's pH, the Henderson-Hasselbalch equation is used with the given methanoic acid concentration of 0.300 moldm^-3, sodium methanoate concentration of 0.500 moldm^-3, and Ka value of 1.6 x 10^-4 moldm^-3, resulting in a pH of approximately 4.02.
Step-by-step explanation:
The question asks to calculate the pH of a buffer solution consisting of 0.300 moldm-3 methanoic acid (HCOOH) and 0.500 moldm-3 sodium methanoate (HCOONa), given the acid dissociation constant (Ka) of methanoic acid as 1.6 x 10-4 moldm-3. By applying the Henderson-Hasselbalch equation, which is pH = pKa + log([A-]/[HA]), we can find the pH of the buffer solution.
To calculate the pH, first determine the pKa from the given Ka value: pKa = -log(Ka) = -log(1.6 x 10-4) = 3.80. Substitute the concentration values of the acid (HA) and its salt (A-) into the equation: pH = 3.80 + log(0.500 / 0.300) = 3.80 + log(1.6667) = 3.80 + 0.2220 = 4.022. Therefore, the pH of the buffer solution is approximately 4.02.