chem question need help solving

Question

What is the pH of a solution that results from diluting 0.50 mol formic acid (HCO2H) and 0.10 mol sodium formate (NaHCO2) with water to a volume of 1.0 L? (Ka of HCO2H = 1.8e10-4)

H = 1.8



10

-

4

Answer 1

[HCO2H] = 0.50 mol/L = 0.50 M

[HCO2-] = 0.10 mol/L = 0.10 M

pKa = -log Ka = -log 1.8x10^-4 = 3.74

Henderson Hasselbalch equation:

pH = pKa + log [salt]/[acid]

pH = 3.74 + log (0.10/0.50)

pH = 3.74 + log 0.2

pH = 3.74 + (-0.699)

pH = 3.04