Pyridine, C5H5N, is a weak base [Kb = 1.78 × 10–9]. — Acid-Base Equilibrium / Solubility Chemistry Question
Problem Context
Pyridine, C5H5N, is a weak base [Kb = 1.78 × 10–9].
Calculate the [OH–] and pH of a 0.240 M solution of pyridine.
Model Answer
pH=9.32
A 20.0 mL portion of 0.240 M pyridine solution is titrated with 0.120 M HCl.
i. Calculate the pH after 20.0 mL of the HCl solution has been added.
Model Answer
(0.240M pyridine) (0.0200L)=0.0048mol pyridine
(0.120M HCl) (0.0200L)=0.0024mol HCl
pH=5.25
ii. Calculate the pH at the equivalence point.
Model Answer
Equivalence point (20.00mL pyridine)(0.240M) + (40.00mL) (0.120M HCl) = 0.0800M pyH+
pH=3.17
If MgCl2 is added to a 0.240 M solution of pyridine, what is the minimum [Mg2+] at which Mg(OH)2 will precipitate?
[Ksp = 5.6 × 10–12]
Model Answer
= 1.3 × 10^-2
For a solution with [Mg2+] = 0.10 M and [C5H5N] = 0.240M what must the [C5H5NH+] be to just prevent the precipitation of Mg(OH)2?
Model Answer
= 5.71 × 10^-4