What would be the magnitude of `EMF` of the following cell`:`

at `25^(@)C` ? The ionization constant of acetic acid, `K_(a)~ 10^(-5)`, while that of formic acid, `K_(a)~10^(-4)`

Options

A. `0.0295V`
B. `0.059V`
C. `-0.059V`
D. `-0.0295V`

Answer

b

Explanation

At anode `:`
`0.1M` acetic acid `+0.1M` sodium acetate `implies` Acidic buffer.
`:. pH_(a)=pK_(a)+log [(sal t)/(Aci d)]" "(pK_(a(CH_(3)COOH))=5)`
`=5+log((0.1)/(0.1))=5`
At cathode `:`
`0.1M` formic acid `+0.1M` sodium formate `implies` Acidic buffer.
`:.pH_(c)=pK_(a)+log((0.1)/(0.1))" "[pK_(a(HCOOH))=4]`
`pH_(c)=4`
`E_(cell)=-0.059(pH_(c)-pH_(a))=-0.059*4-5)=0.059V`