The indicator constant for an acidic indicator, `HIn` is `5xx10^(-6)M`. This indicator appears only in the colour of acidic form when `([In])/([HIn])le(1)/(20)` and it appears only in the colour of basic form when `([HIn])/([In])le(1)/(40)` . The pH range of indicator is `[` Given `: log 5=0.7]`

Options

A. `4.3-6.3`
B. `4.0-6.6`
C. `4.0-6.9`
D. `3.7-6.6`

Answer

3

Explanation

`pH=P_(ki n)+log_(10)[(ln^(-))/(Hln)]`
`pH=[6-log_(10)5]+log_(10)[(1)/(20)]=4`
`PH=P_(k i n)+log_(10)[(ln^(-))/(Hln)]`
`=P_(ki n)+log_(10)[(40)/(1)]`
`=6-log_(10)5+log_(10)40`
`=6-0.7+1.6=6.9`