Codeine C18H21NO3 is a weak organic base. A 5.0 x 10^-3 M solution of codeine has a pH of 9.95. Calculate the value of Kb for this substance. What is the pKb for this base?

Respuesta :

Answer:

Kb = [tex]4.45\times10^{-7}\ mol/L[/tex]

[tex]p^{Kb}=6.35[/tex]

Explanation:

For a weak organic base, the formula to find [tex]p^{OH}[/tex] is given by:

[tex]p^{OH}=p^{K_b}+\log c[/tex]

where c is the concentration of base.

Here c= [tex]5\times10^{-3}\ M[/tex]

[tex]p^{H}=9.95\\p^{OH}=14-p^{H}=14-9.95=4.05[/tex]

Substituting the above values in the formula,we get:

[tex]p^{k_b}=p^{OH}-\log c\\p^{k_b}=4.05-\log (5\times10^{-3})\\p^{K_b}=6.35\\K_b=$antilog 6.35=4.45\times10^{-7}\ mol/L[/tex]

Hence:

Kb = [tex]4.45\times10^{-7}\ mol/L[/tex]

[tex]p^{Kb}=6.35[/tex]