CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
An unknown monoprotic weak acid, HX, has pKa=4.75 at 25 °C. Two separate solutions are prepared: Solution A is 0.050 M HX(aq) and Solution B is 0.0050 M HX(aq), both at 25 °C.
(a) Convert the given pKa value to Ka.
(b) Determine the percent ionization of the acid in Solution A.
(c) Determine the percent ionization of the acid in Solution B.
(d) By what factor does the percent ionization change when the concentration is decreased from 0.050 M to 0.0050 M? Show numerical support for your answer.
(e) Justify the trend observed in parts (b)–(d) using principles of chemical equilibrium.