A 100 mL sample of 0.100 M aqueous acetic acid, CH3COOH
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
A 100 mL sample of 0.100 M aqueous acetic acid, CH3COOH, is at equilibrium with its ions at 25 °C. (The acid-dissociation constant for acetic acid is Ka=1.8×10−5.) The sample is then transferred to a 1.000 L volumetric flask and diluted to the mark with distilled water, keeping the temperature constant.
(a) Calculate the pH of the original 0.100 M acetic acid solution before dilution. Show all steps.
(b) Calculate the molar concentration of undissociated CH3COOH and of acetate ion, CH3COO−, in the original solution.
(c) Immediately after the dilution (before any reaction occurs), determine the new molar concentration of CH3COOH present in the flask.
(d) After equilibrium is re-established in the diluted solution, calculate the new pH. Include a clearly labeled ICE (initial-change-equilibrium) table or an equivalent systematic method in your work.
(e) Compare the percent ionization of acetic acid before and after dilution. Explain how the change you observe is consistent with the shift predicted for the equilibrium.