CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
Ammonia, NH₃, is titrated with hydrochloric acid. A chemist places 50.0 mL of 0.150 M NH₃ (Kb=1.8×10−5) in a beaker and adds 0.300 M HCl from a buret until exactly one equivalence point is reached.
(a) Calculate the volume (in mL) of HCl delivered to reach the equivalence point.
(b) Determine the molar concentration of ammonium ions, NH₄⁺, present at the equivalence point.
(c) Using appropriate equilibrium calculations, determine the pH of the solution at the equivalence point. Express the final pH to two decimal places.
(d) Methyl orange changes color in the pH range 3.1 – 4.4. Would methyl orange provide a sharp endpoint for this titration? Justify your answer quantitatively.