Question

Calculate the pH of a buffer solution that is 0.200 M HC₂H₃O₂ and 0.100 M NaC₂H₃O₂. Ka = 1.8 x 10⁻⁵.

Answer 1

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.