A 0.02 M solution of pyridinium hydrochloride has pH=3.44. Calculate the ionization constant of pyridine.

A 0.02 M solution of pyridinium hydrochloride has pH=3.44. Calculate t

1.	A 0.02 M solution of pyridinium hydrochloride has pH=3.44. Calculate the ionization constant of pyridine.
Answer» <html><body><p></p>Solution :`pH = 3.44 , i.e., log [H^(+)]=-3.44 = bar(4).56 :.[H^(+)]=3.63xx10^(_4)M` <br/> `C_(5)H_(5)N.HCl+aq hArr C_(5)H_(5)overset(+)<a href="https://interviewquestions.tuteehub.com/tag/ncl-570043" style="font-weight:bold;" target="_blank" title="Click to know more about NCL">NCL</a>^(-)+H^(+)` <br/> `K_(a)=([C_(5)H_(5)overset(+)NCl^(-)][H^(+)])/([C_(5)H_(5)N.HCl])=((3.63xx10^(-4))(3.63xx10^(-4)))/(2xx10^(-2))=6.588xx10^(-6)` <br/> `pK_(a)=-log(6.588xx10^(-6))=6-0.8187=5.<a href="https://interviewquestions.tuteehub.com/tag/18-278913" style="font-weight:bold;" target="_blank" title="Click to know more about 18">18</a>` <br/> `pK_(a)+pK_(b)=14 :. pK_(b)=14-5.18 = 8.82` <br/> `-log K_(b) = 8.82 or log K_(b) = - 8.82 = bar(-).18 :. K_(b)=1.514xx10^(-9)` <br/> Alternatively, Pyridine hydrochloride is a salt of weak <a href="https://interviewquestions.tuteehub.com/tag/base-892693" style="font-weight:bold;" target="_blank" title="Click to know more about BASE">BASE</a> and strong acid . <a href="https://interviewquestions.tuteehub.com/tag/hence-484344" style="font-weight:bold;" target="_blank" title="Click to know more about HENCE">HENCE</a>, <br/> `pH=-(1)/(2)[log K_(w)-logK_(b)+logc],i.e., 3.44 = - (1)/(2) [-14-logK_(b)+log(2xx10^(-2))]` <br/> or `6.88=14+log K_(b) + 1.70 or log K_(b) = - 8.82 = bar(9).18 or K_(b)=1.5xx10^(-9)`.</body></html>