Calculate the pH of a solution composed of 155mL of 0.1 M acetic acid and 45 g of sodium acetate. The pKa of acetic acid is 4.76.
MY ANSWER:
pH = 4.76 + log(3.53M/0.1M)
pH = 6.31
To calculate the pH of the solution, you can use the Henderson-Hasselbalch equation, which relates the pH of a solution to the pKa of the acid and the concentrations of the acid and its conjugate base.
The Henderson-Hasselbalch equation is: pH = pKa + log([A-]/[HA])
Where:
- pH is the logarithmic measure of the concentration of hydrogen ions in the solution.
- pKa is the logarithmic measure of the acidity of the acid.
- [A-] is the concentration of the conjugate base (in this case, sodium acetate).
- [HA] is the concentration of the acid (in this case, acetic acid).
Given:
- pKa = 4.76 (the acidity constant of acetic acid)
- [A-] = 45 g of sodium acetate (To convert grams to moles, divide by the molar mass of sodium acetate: 45 / (82.03 g/mol) = 0.548 mol)
- [HA] = 0.1 M (The molarity of acetic acid is already given)
Now we can plug these values into the equation:
pH = 4.76 + log(0.548/0.1)
pH = 4.76 + log(5.48)
pH = 4.76 + 0.739
pH = 5.499
Therefore, the pH of the solution is approximately 5.50.