Final answer:
The pH of the buffer solution, we use the Henderson-Hasselbalch equation with the given concentrations and the dissociation constant Ka. After doing the math, the pH of the buffer solution is found to be 4.44.
Step-by-step explanation:
The question asks to calculate the pH of a buffer solution containing 0.200 M HC₂H₃O₂ (acetic acid) and 0.100 M NaC₂H₃O₂ (sodium acetate). The dissociation constant Ka for acetic acid is 1.8 x 10⁻⁵.
To calculate the pH of the buffer, we use the Henderson-Hasselbalch equation, which is given by:
PH = pKa + log([A⁻]/[HA])
Where:
- pKa is the negative logarithm of the Ka value for acetic acid.
- [A⁻] is the concentration of the acetate ion, which comes from the sodium acetate.
- [HA] is the concentration of acetic acid.
First, we calculate the pKa:
pKa = -log(Ka) = -log(1.8 x 10⁻⁵) = 4.74
Now we can plug in the values to the Henderson-Hasselbalch equation:
PH = 4.74 + log(0.100/0.200)
The ratio [A⁻]/[HA] is 0.100/0.200 = 0.5
PH = 4.74 + log(0.5)
PH = 4.74 + (-0.3010)
pH = 4.44
The pH of the buffer solution is 4.44.