1.

What will be the pH of 4xx10^(-5)M A_(2)B solution which is assumed to be dissociated 75% in water. [Given : K_(b)(AHO)=5xx10^(-9),H_(2)B is strng acid.]

Answer»


Solution :`{:(""A_(2)B""hArr""2A^(+)""+""B^(2-)),(4xx10^(-5)xx0.25""2xx4xx10^(-5)xx0.75""0.75xx4xx10^(-5)),(""10^(-5)""(6XX10^(-5)-X)""3xx10^(-5)):}`
`{:(A^(+)+""H_(2)O""hArr""AOH+H^(+)),((6xx10^(-5)-x)""x ""x):}`
or `(10^(-5))/(5)=(x^(2))/((6xx10^(-5)-x))`
or `5x^(2)=6xx10^(-10)-x xx10^(-5)`
`5x^(2)+10^(-5)x+6xx10^(-10)=0`
or `x=(-10^(-5)+SQRT(10^(-10)+120xx10^(-10)))/(10)`
`x=(-10^(-5)+10^(-5)xxsqrt(121))/(10)`
`x=(10^(-5)(11-1))/(10)=10^(-5)`
`pH=5`


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