Question

`NO_(3)^(-)toNO_(2)` (acid medium) `E^(0)=0.790V`
`NO_(3)^(-)toNH_(3)OH^(+)` (acid medium) `E^(0)=0.731V`.
At what `pH`, the above two will have same `E` value ? Assume the concentration of all other species `NH_(3)OH^(+)` except `[H^(+)]` to be unity.

Answer 1

Correct Answer - `pH=1.5`
`overset(+5)(N)O_(3)^(-)+2H^(+)+e^(-)tooverset(+4)(N)O_(2)+H_(3)O,0.79"volt"`
`overset(+5)(N)O_(3)^(-)+8H^(+)+6e^(-)toNH_(3)OH^(+)+2H_(2)O,0.731"volt"`
`E=0.79-(0.0591)/(1)log((1)/([H^(+)]^(2)))=0.731-(0.591)/(6)log((1)/([H^(+)]^(8)))`
`0.059=0.059(2-(8)/(6))pHimpliespH=(6)/(4)=1.5`