1.

For Cr_(2)O_(7)^(2-)(aq)+14H^(+)(aq)+6e^(-) to 2Cr^(3+)(aq)+7H_(2)O(aq) E^(@)=1.33" V". At [Cr_(2)O_(7)^(2-)]=4.5" millimole" , [Cr^(3+)]=15" millimole", E is1.067" V". The pH of the solution is :

Answer»

SOLUTION :`-E_(cell)=-((772xx1000" CV "mol^(-1)))/((4)xx(96500" C " mol^(-1)))=2V` ltbr? For the given reaction :
`Cr_(2)O_(7)^(2-)(aq)+14H^(+)(aq)+6e^(-) to 2Cr^(3+)(aq)+7H_(2)O(aq)`
`1.067=1.33-(0.0591)/(6)"log"([Cr^(3+)]^(2)[H_(2)O]^(7))/([Cr_(2)O_(7)^(2-)][H^(+)]^(14))`
`1.067=1.33-9.85xx10^(-3)"log"((15xx10^(-3))^(2)xx(1)^(7))/((4.5xx10^(-3))[H^(+)]^(14))`
`2 log[15xx10^(-3)]-log[4.5xx10^(-3)]-14" log "[H^(+)]=(0.263)/(9.85xx10^(-3))`
`2xx(-1.82)+2.34+14 pH=26.7`B
`14 pH=26.7+1.3=28`
`pH=(28)/(14)=2`.


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