Respuesta :
Answer:
Amount of pyridine required = 0.0316 M
Explanation:
pH of a buffer solution is calculated by using Henderson - Hasselbalch equation.
[tex]pH=pK_a+log\frac{[Conjugate\ base]}{[weak\ acid]}[/tex]
Pyridinium is a weak acid and in the presence of its conjugate base, it acts as buffer.
Henderson - Hasselbalch equation for pyridine/pyridinium buffer is as follows:
[tex]pH=pK_a+log\frac{[Py]}{PyH^+]}[/tex]
pH = 4.7
[tex]pK_a=5.2[/tex]
[tex]PyH^+[/tex] (Pyridinium)=0.100 M
Substitute the values in the formula
[tex]pH=pK_a+log\frac{[Py]}{PyH^+]}\\4.7=5.2 log\frac{[Py]}{0.100}[/tex]
[tex]4.7-5.2=log\frac{[Py]}{0.100} \\-0.5=log\frac{[Py]}{0.100}\\\frac{[Py]}{0.100}=antilog -0.5\\\frac{[Py]}{0.100}=0.316[/tex]
[tex]\frac{[Py]}{0.100} =0.316[/tex]
[Py]=0.0316\ M
Amount of pyridine required = 0.0316 M
