Question

Consider the titration of 100.0 mL of 0.200 M acetic acid by 0.100 M KOH. Calculate the pH of the resulting solution after 200 mL of KOH have been added. (For acetic acid, ( K_a = 1.8 times 10^(-5) ))

a) 3.74
b) 4.24
c) 4.74
d) 5.24

Answer 1

The initial pH of the acetic acid solution can be calculated using the ICE approach. The final pH of the resulting solution after adding 200 mL of KOH is the same as the initial pH.

Step-by-step explanation:

The initial pH of the acetic acid solution can be calculated using the ICE approach. The formula for acetic acid is CH3COOH, and its Ka value is 1.8 × 10^(-5). The concentration of acetic acid is 0.200 M, so the initial concentration of H3O+ can be calculated as √(Ka × [CH3COOH]) = √(1.8 × 10^(-5) × 0.200) = 1.32 × 10^(-3) M. Therefore, the initial pH is -log(1.32 × 10^(-3)) = 2.879.

When 200 mL of 0.100 M KOH is added to the acetic acid solution, it will react with the acetic acid to form acetate ion (CH3COO-) and water. The volume of the resulting solution will be 100.0 mL + 200 mL = 300.0 mL. At this point, the titration is not yet at the equivalence point, so the pH is not affected by the acetate ion. Therefore, the pH of the resulting solution after 200 mL of KOH have been added is also 2.879.