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Pyridine is a weak base that is used in the manufacture of pesticides and plastic resins. It is also a component of cigarette smoke. Pyridine ionizes in water as follows: C5H5N+H2O⇌C5H5NH++OH− The pKb of pyridine is 8.75. What is the pH of a 0.460 M solution of pyridine? (Assume that the temperature is 25 ∘C.) Express the pH numerically to two decimal places.

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onyebuchinnaji

Answer:

The pH of the solution is 9.46

Explanation:

         C₅H₅N + H₂O ⇌ C₅H₅NH+OH⁻

I          0.46

C         - x                           +x +x

E         0.46 - x                        

-LogKb = Pkb

[tex]Kb =10^{[-PKb]} = 10^{[-8.75]} = 1.778 X 10^{-9}[/tex]

[tex]Kb = \frac{[C5H5NH][OH^-]}{[C5H5N]}[/tex]

[tex]1.778 X10^{-9}= \frac{X^2}{0.46-X} \\\\X^2 = 8.1788 X 10^{-10} - 1.778 X10^{-9}X\\\\X^2 + 1.778 X10^{-9}X -8.1788 X 10^{-10}\\\\X = 2.85977 X 10^{-5} = [OH^-][/tex]

pOH = -Log[OH⁻]

pOH = -Log [2.85977 x 10⁻⁵]

pOH = 4.54

pOH + pH = 14

pH = 14 - pOH

pH = 14 - 4.54

pH = 9.46

Therefore, the pH = 9.46

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