The standard electrode potential for the two electrode `A^(+)//A and B^(+)//B` are respectively 0.5V and 0.75V. The emf of the given cell `A|A^(+)(a=1)||B^(+)(a=1)|` B will be

Options

A. 1.25 V
B. `-1.25 V`
C. `-0.25 V`
D. `0.25 V`

Answer

D

Explanation

`A | A^(+) (a = 1) || B^(+)(a =1) | B`
EMF `= E_("cathode") - E_("anode") = 0.75 - (0.5)`, EMF = 0.25 V