The weak acid HX has an acid-dissociation constant at
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
The weak acid HX has an acid-dissociation constant Ka=4.5×10−6 at 25∘C. Two separate solutions of HX are prepared: Solution 1 is 0.050M and Solution 2 is 0.0050M.
(a) Without performing detailed calculations, predict which solution has the greater percent ionization and explain your reasoning.
(b) A student measures the percent ionization of Solution 1 to be 2.1%. Assuming the value of Ka is constant, estimate the percent ionization expected for Solution 2 and outline your reasoning steps.
(c) Explain qualitatively why the percent ionization actually observed for very dilute solutions like Solution 2 may differ from the estimate in part (b). In your explanation, discuss the role of water’s autoionization and its impact on calculated Ka values if it is ignored.