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What is the value of pK(b)(CH(3)COO^(c-)...

What is the value of `pK_(b)(CH_(3)COO^(c-))` if `wedge^(@)._(m)=390 S cm^(-1) mol ^(-1)` and `wedge_(m)=7.8 S cm^(2) mol^(-1)` for `0.04 M` of `CH_(3)COOH` at `25^(@)C`?

A

`9.3`

B

`9.2`

C

`4.7`

D

`4.8`

Text Solution

Verified by Experts

The correct Answer is:
b
`alpha=(wedge_(m))/(wedge^(@)._(m))=(7.8)/(390)=0.02`
`K_(A(ch_(3)cooh))=(calpha.calpha)/(c-calpha)`
`=(calpha^(2))/(1-alpha)=(0.04xx(0.02)^(2))/(1-0.02)~~!.6xx10^(-5)`
Use`:pK_(a)+pK_(b)=pK_(w)=14`
`impliespK_(b)=14-pK_(a)=14-4.8=9.2`
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