For `Cr_(2)O_(7)^(2)+14 H^(+)+6e^(-)rarr2Cr^(3+)+7H_(2)O`
`E^(@)=1.33 V.At 298 k, [Cr_(2)O_(7)^(2-)] =4.5` millimole
`[Cr^(3+)]=15` millimole ,E is 1.067 v The pH of the solution is nearly eual to

Options

A. 2
B. 3
C. 5
D. 4

Answer

A

Explanation

`Cr_(2)O_(7)^(2-)+14 HG^(+)+6e^(-)rarr2Cr^(3+)+7 H_(2)O`
`E=E^(@)=-(0.059)/(n) log[(Cr^(3+))]^(2)[(H_(2)O^(7))]/[(Cr_(2)O_(7)^(2-)][H^(+)]^(14)`
`1.067 =1.33 -0.059/6 log 15xx10^(-3)(1^(7))/(4.5xx10^(-3))[H^(+)]^(14)`
or `+14 pH =28.041`
`pH=(28.041)/(4)=2`