What is the pH of a buffer containing 40.0 mmol/L NaHC2O4 and 4.0 mmol/L H2C2O4, given pKa = 1.25?

To determine the pH of a buffer solution consisting of sodium hydrogen oxalate (NaHC₂O₄) and oxalic acid (H₂C₂O₄), the Henderson-Hasselbalch equation is typically used. This equation is particularly useful for buffer solutions, as it relates the pH to the pKa and the concentrations of the acidic and basic components of the buffer.

The Henderson-Hasselbalch equation is stated as follows:

[ \text{pH} = \text{pKa} + \log\left(\frac{[\text{Base}]}{[\text{Acid}]}\right) ]

In this scenario, the base is represented by NaHC₂O₄, and the acid is represented by H₂C₂O₄. We have:

• pKa = 1.25

• Concentration of the base (NaHC₂O₄) = 40.0 mmol/L

• Concentration of the acid (H₂C₂O₄) = 4.0 mmol/L

Substituting these values into the equation entails first calculating the ratio of the concentrations:

[ \frac{[\text{Base}]}{[\