CHEMISTRY · Multi-part · AP · Chemistry · Acids and Bases · Acids and Bases
Problem
A chemist dissolves 0.180g of a weak, monoprotic base B (molar mass 73.0gmol−1) in enough water to make 250.0mL of solution at 25∘C. The measured pH of the solution is 11.62.
(a) Calculate the hydroxide-ion concentration [OH−] in the solution.
(b) Determine the initial molarity of base B before ionization occurs.
(c) Using the data from parts (a) and (b), compute the base-dissociation constant Kb and the corresponding pKb for B.
(d) Calculate the percent ionization of base B in this solution.
(e) Using the relationship between Ka and Kb, determine pKa for the conjugate acid HB+. Comment on the relative acidic strength of HB+ compared with NH4+ (pKa=9.25).