Question

Assuming 0.40 m of ha and 0.05 m of naa with a ka of 2.45x10⁻⁴, what is the pH of this solution?

a) 2.74
b) 3.20
c) 4.63
d) 5.35

Answer 1

The pH of the solution is approximately 3.20.

Step-by-step explanation:

The pH of a solution can be calculated using the equation: pH = -log[H+]. In this case, we have information about the concentration of HCO₂H (0.40 M) and its conjugate base HCO₂Na (0.05 M). The pKa of formic acid (HCO₂H) is given as 3.75. Since HCO₂H is a weak acid, we can use the Henderson-Hasselbalch equation to find the pH:

pH = pKa + log([conjugate base]/[acid]) = 3.75 + log(0.05/0.40) ≈ 3.20

Therefore, the pH of this solution is approximately 3.20, so the correct answer is b) 3.20.