Question

Calculate the pH of a buffer solution that contains 0.2 moles of acetic acid (CH3COOH) and 0.1 moles of sodium acetate (NaCH3COO) dissolved in one liter of solution. The dissociation constant of acetic acid is 1.8 x 10^-5.

Answer 1

To calculate the pH of the buffer solution, we can use the Henderson-Hasselbalch equation:pH = pKa + log  [A-]/[HA] where pH is the pH of the solution, pKa is the negative logarithm of the acid dissociation constant  Ka , [A-] is the concentration of the conjugate base  acetate ion, CH3COO- , and [HA] is the concentration of the weak acid  acetic acid, CH3COOH .First, we need to find the pKa value. The pKa is the negative logarithm of the Ka:pKa = -log Ka  = -log 1.8 x 10^-5   4.74Now, we can use the Henderson-Hasselbalch equation to find the pH of the buffer solution:pH = 4.74 + log  [0.1]/[0.2] pH = 4.74 + log  0.5 pH  4.74 - 0.3pH  4.44So, the pH of the buffer solution is approximately 4.44.