Question

Calculate the pH of $1.0L$ of $0.10M$ pyridine solution to which $0.3mol$ of pyridinium chloride $C_5{H}_{5}N{H}^{+}Cl$, has been added, assuming no change in volume.

Answer 1

After nursing base and its ball, a buffer solution will be form of a weak base and salt of its conjugate acid

Menderson Hassilbatch equation will be used to solve

$pOH=p^{k_b}+\log$ [conjugate and weak base]

Value of $k_b$ can be taken from literature $=1.5\times {10}^{-9}$

$\left[C_3{H}_{5}N\right]=$ [weak base] $=0.1M$

$\left[C_3{H}_{5}N{H}^{+}C{l}^{-}\right]=$ [Conjugate acid] $=0.3M$

$pOH=-\log \left(1.5\times {10}^{-9}\right)+\log \left(\frac{0.3}{0.1}\right)$

$pOH=8.8239+0.47712$

$pOH=9.30$

$pH+pOH=14$

$pH=14-9.30$

$pH=4.69$